Fluctuation of plastid genetics in angiosperm Sodmergen College of Life Sciences Peking ...

30 Pages·2008·0.9 MB·German

PlantCellPhysiol.49(6):958–968(2008)
doi:10.1093/pcp/pcn069,availableonlineatwww.pcp.oxfordjournals.org
(cid:1)TheAuthor2008.PublishedbyOxfordUniversityPressonbehalfofJapaneseSocietyofPlantPhysiologists.
Allrightsreserved.Forpermissions,pleaseemail:[email protected]
Occurrence of Plastids in the Sperm Cells of Caprifoliaceae: Biparental Plastid
Inheritance in Angiosperms is Unilaterally Derived from Maternal Inheritance
Yingchun Hu, Quan Zhang, Guangyuan Rao and Sodmergen*
KeyLaboratoryofCellProliferationandDifferentiation(MinistryofEducation),CollegeofLifeSciences,PekingUniversity,Beijing
100871,PRChina
Itiswidelyheldthatorganellesinheritfromthematernal the mitochondrial genome (Ankel-Simons and Cummins
lineage. However, the plastid genome in quite a few angio- 1996, Mogensen 1996). For plastids, maternal (Correns D
o
sperms appears to be biparentally transmitted. It is unclear 1909)andbiparental(Baur1909)transmissionwereinitially w
n
how and why biparental inheritance of the genome became characterizedinMirabilisandPelargonium,respectively,and loa
d
activated.Here,wedetectedwidespreadoccurrenceofplastids it has been shown that the genome is inherited in a diverse e
d
inthespermcells(acellularprerequisiteforbiparentalinher- manner, i.e. maternally in the majority and biparentally in fro
m
itance) of traditional Caprifoliaceae. Of the 12 genera the minority of angiosperm species (Tilney-Bassett 1978, h
sampled, the sperm cells of Abelia, Dipelta, Heptacodium, Kuroiwa1991).Todate,thegeneticregulationofmaternal ttp
s
Kolkwitzia,Leycesteria,Linnaea,Lonicera,Symphoricarpos, inheritance is unclear, despite the fact that elimination of ://a
Triosteum and Weigela possessed inheritable plastids. The paternalplastidsinmalereproductivecellsisakeyfactor(for ca
d
other genera, Sambucus and Viburnum, lacked plastids in reviews,seeHagemannandSchro¨der1989,Mogensen1996). e
m
sperm cells. Interestingly, such exclusion of plastids in the The elimination of paternal plastids occurs at various ic
.o
spermcellsofsomeCaprifoliaceaeappearedtobeassociated stages of pollen development, including plastid exclusion u
p
withthedivergenceofDipsacalesphylogeny.Closerexamina- during the first pollen mitosis (Lycopersicon-type) and .co
m
tionofWeigelafloridarevealedthatbothplastidsandplastid plastid degeneration in the generative and sperm cells /p
c
DNA were highly duplicated in the generative cells. This (Solanum-type; Hagemann and Schro¨der 1989). Another p
/a
impliesthattheappearanceofplastidsinspermcellsinvolved possible way to eliminate paternal plastids is exclusion of rtic
cellularmechanisms.Becausesuchmechanismsmustenhance sperm cytoplasm during fertilization, as reported in le
-a
thestrengthofplastidtransmissionthroughthepaternalline- Hordeum vulgare (Mogensen 1988); however, this is not b
s
age and appear ubiquitous in species exhibiting biparental or well supported because H. vulgare is more probably a tra
c
potential biparental plastid inheritance, we presume that Lycopersicon-type species (Mogensen and Rusche 1985, t/4
9
biparental plastid genetics may be a derived trait in angio- Sodmergen et al. 2002). After plastid elimination, the /6
sperms. This is consistent with our extended phylogenetic mature male reproductive cells are free of intact plastids /95
8
analysis using species with recently discovered modes of andplastidDNA(HagemannandSchro¨der1989,Kuroiwa /1
8
potential plastid inheritance. The results show thatbasal and 1991).Thisdeterminesmaternalinheritanceinangiosperms 12
1
earlyangiospermshavematernalplastidtransmission,whereas and largely facilitates the identification of species having 0
1
all potential biparental transmission occurs at terminal maternal inheritance. By visually confirming the lack of b
y
branchesofthetree.Thus,unlikepreviousstudies,wesuggest plastid nucleoids in male reproductive cells, Corriveau and gu
e
thatbiparentalplastidinheritanceinangiospermswasunilat- Coleman (1988) and Q. Zhang et al. (2003) demonstrated s
t o
erallyconvertedfromthematernaltransmissionmodeduring that (cid:1)80% of angiosperm species display maternal plastid n
0
lateangiospermevolution. inheritance. However, these studies still detected the 3
A
occurrence of inheritable plastids in cells of (cid:1)20% of p
Keywords: Angiosperm — Caprifoliaceae — Non- angiosperm species (Corriveau and Coleman 1988, Q. ril 2
0
Mendelian genetics — Plastid inheritance. Zhang et al. 2003). Because plastids in male reproductive 19
Abbreviations:DAPI,40,6-diamidino-2-phenylindole;DiOC , cells are potentially transmitted to the zygote, the cytolog-
6
3,30-dihexyloxacarbocyanineiodide. ical trait of occurrence of plastids in these cells is termed
‘potential biparental plastid inheritance’. Comparing this
cytological evidence with knowngenetic data, it was found
that, with few exceptions, potential biparental plastid
Introduction inheritance appears in good agreement with biparental
transmission (Miyamura et al. 1987, Corriveau and
It is accepted that extranuclear genomes are inherited Coleman 1988, Nagata et al. 1999). Therefore, it can be
throughthematernallineage,andthisiswellestablishedfor suggestedthat biparental inheritance of theplastid genome
*Correspondingauthor:E-mail,[email protected];Fax,þ86-10-62751526.
958
Fluctuationofplastidgeneticsinangiosperm 959
emerged at a distinct rate, probably up to 20%, at the Diervillaceae and Linnaeaceae, comprises 13 genera (Bell
species level in angiosperms. etal.2001,Donoghueetal.2003;W.H.Zhangetal.2003).
Why does biparental inheritance of plastids appear Weinitiallyexaminedplantsfromthe12generaavailablein
to be widespread in angiosperms? This is related to the China,byvisuallyinspectingmaturemalereproductivecells
fundamental question of how non-Mendelian genetics for the presence of plastid DNA. Mature pollen grains
benefit eukaryotes. Birky (1995) addressed this issue by of the species listed in Table 1 were sampled, stained with
conducting a concise phylogenetic analysis. The study 40,6-diamidino-2-phenylindole (DAPI) and examined by
examined the mode of plastid inheritance in ancestral epifluorescence microscopy. Except for V. sargentii, which
angiosperms and produced equivocal results, finding that hasbicellularpollen,thepollenofallspecieswastricellular,
plastid inheritance had alternated frequently between withtwospermandonevegetativecell.AsshowninFig.1,
D
maternal and biparental modes during angiosperm phylog- wedetectedfluorescentnucleoidsassociatedwiththesperm o
w
eny. It was therefore suggested that plastid inheritance had nuclei of Abelia biflora, Dipelta floribunda, Heptacodium nlo
evolvedmanytimesinangiospermphylogenyinresponseto miconioides, Kolkwitzia amabilis, Leycesteria formosa, ad
e
vwaerydiensgcrainbde caogmepnleerxalsepleactttieornnpthreastsudrieffser(Bsifrrkoym19t9h5e).aHboevree LTirnionsateeaumbopreinanlias,tiLfiodnuimceraandmaWacekigiie,laSyfmloprihdoar.icIanrpcoosnstrinaesnt,siisn, d from
study in terms of the fluctuation of plastid genetics in Sambucus williamsii and Vibernum sargentii, no such h
angiosperms.Theoccurrenceofpotentialbiparentalinheri- nucleoids were associated with the sperm or generative ttps
tanceintraditionalCaprifoliaceaeprovidedavaluableclue nuclei. The fluorescent nucleoids correspond to organellar ://a
c
for our study. The results suggest that plastid inheritance DNA in male reproductive cells (see below), and indicate ad
e
was initially uniparental, and that biparental transmission potential organelle transmission from the paternal lineage. m
ic
derived unilaterally from the maternal transmission mode TheresultsshowninFig.1thusindicatematernalorganelle .o
u
during recent angiosperm evolution. p
transmission in two genera (defined here as pattern I), .c
o
including the outgroup Adoxa moschatellina, and potential m
Results biparentalorganelleinheritancein10genera(patternII)of /pc
p
Caprifoliaceae (Table 1). /a
Potential biparental plastid inheritance in Caprifoliaceae To determine whether the observed nucleoid fluores- rticle
The traditional Caprifoliaceae family, which was cence corresponded to plastid and/or mitochondrial DNA, -a
b
s
recently classified into Adoxaceae, Caprifoliaceae, we next performed electron microscopy, immunoelectron tra
c
t/4
9
Table 1 Plastids, mitochondria, plastid DNA and mitochondrial DNA in the mature generative or sperm cells of /6
/9
traditional Caprifoliaceae 5
8
/1
8
Species Epifluorescence microscopy Electron Immunoelectron 1
2
microscopy microscopy 10
1
DAPI staining DAPI–DiOC6 staining pt/mt ptDNA/mtDNA by
Cell type/pattern ptDNA/mtDNA g
u
e
Sambucus williamsii M3/I /(cid:2) (cid:2)/þ /(cid:2)a st o
Viburnum sargentii M2/I /(cid:2) (cid:2)/þ /(cid:2)a n 0
Abelia biflora B3/II þ/(cid:2) þ/þ 3 A
DHieppetlatacofdloiurmibumndicaonioides BB33//IIII pril 2
0
1
Kolkwitzia amabilis B3/II þ/(cid:2) þ/þ 9
Leycesteria formosa B3/II
Linnaea borealis B3/II
Lonicera maackii B3/II þ/(cid:2) þ/þ þ/(cid:2)a
Symphoricarpos sinensis B3/II
Triosteum pinnatifidum B3/II
Weigela florida B3/II þ/(cid:2) þ/þ þ/(cid:2)a
Adoxa moschatellina (outgroup) M3/I (cid:2)
B3,tricellularpollenwithpotentialbiparentalorganelleinheritance;M2,bicellularpollenwithpotentialmaternalorganelleinheritance;
M3,tricellularpollenwithpotentialmaternalorganelleinheritance;ptDNA,plastidDNA;mtDNA,mitochondrialDNA;pt,plastid;mt,
mitochondrion.
aThenumberofgoldparticlesindicatedlowlevelsofmitochondrialDNA.
960 Fluctuationofplastidgeneticsinangiosperm
microscopy and DAPI–DiOC (3,30-dihexyloxacarbocya- suggesting that the fluorescent nucleoids in the sperm cells
6
nine iodide) double staining fluorescence microscopy on of pattern II species correspond to plastid DNA.
pollen cells for six species: S. williamsii and V. sargentii DAPI–DiOC double staining confirmed the above
6
for pattern I transmission, and A. biflora, K. amabilis, results. Because carbocyanine DiOC stains membranes,
6
L. maackii and W. florida for pattern II transmission. The mitochondriawithcristaearemuchmoreintensivelystained
resultsaresummarizedinTable1,andimagesforW.florida and emit remarkably stronger fluorescence than plastids.
and V. sargentii are shown in Fig. 2. Double staining is therefore routinely used to distinguish
In all pattern II species examined, mature sperm cells mitochondria from plastids under epifluorescence micros-
had both plastids and mitochondria (Fig. 2a), whereas in copy (Nagata et al. 1999). The cell sections were first
pattern I species only mitochondria were observed in the observed under UV excitation to detect nucleoid fluores-
D
generative or sperm cells (Fig. 2d). Extensive observation cence and then under blue excitation to observe mitochon- o
w
through serialsectionsconfirmed theabsence ofplastids in drial fluorescence. The nucleoid fluorescence in the sperm nlo
thecellsofpatternIspecies.Weexaminedtheearlierstages cells of pattern II species did not correspond to the ad
e
ospfepcoielsleanredeevxeclloupdmedendturainndgtfhoeunfidrstthpaotllpelnasmtiidtsosoisf(pFaitgte.r2ne)I, mofitopclahsotinddrDiaNlfAlu.orWesecencocenc(lFuidge.2tch)aatndpothteunstwiaalsbinipdaicreantitvael d from
which indicates that pattern I species exhibit Lycopersicon- plastid inheritance occurs in 10 of the 12 Caprifoliaceae h
typeplastidtransmission,themostcommonmechanismfor genera that we examined. ttps
maternalplastidinheritanceinangiosperms(forreferences, ://a
c
a
seeHagemannandSchro¨der1989).Weperformedimmuno- Duplication of plastids and plastid DNA d
e
m
electron microscopy on both pattern I and II species to ToidentifyhowplastidsandplastidDNAarepreserved ic
verifythelocalizationofDNAintheorganelles.Theresults in the sperm cells of pattern II species, we intensively .ou
p
showed strong and consistent localization of gold particles examinedthegenerativeandspermcellsofW.floridausing .c
o
on plastids of pattern II species (Fig. 2b), indicating that serial electron microscopy. Our observations detected m
/p
plastids in these sperm cells contained large amounts of ‘dividing plastids’ in the generative cells that were peeling c
p
DNA. In contrast, the mitochondria in the cells of both offthepollenintine.Afewplastidsinthecellsofthisstage /a
pattern types consistently showed no labeling (Fig. 2b, f), were dumbbell-shaped, with distinct plastid division rticle
-a
b
s
tra
c
t/4
9
/6
/9
5
8
/1
8
1
2
1
0
1
b
y
g
u
e
s
t o
n
0
3
A
p
ril 2
0
1
9
Fig.1 PollencellsoftraditionalCaprifoliaceaespeciesstainedwithDAPI.Fluorescentgranules(aggregates),whichindicatethepaternal
contributionofcytoplasmicDNA,appeartobeassociatedwiththespermnucleiofA.biflora,D.floribunda,H.miconioides,K.amabilis,
L. formosa, L. borealis, L. maackii, S. sinensis, T. pinnatifidum and W. florida but not with the sperm nuclei of S. williamsii or
A.moschatellinaorthegenerativenucleusofV.sargentii.GN,generativenucleus;VN,vegetativenucleus;SN,spermnucleus.
Fluctuationofplastidgeneticsinangiosperm 961
(c)
DAPI
DiOC
D
o
w
n
lo
a
DAPI d
e
+ d
DiOC fro
m
h
ttp
s
://a
c
a
d
e
m
ic
.o
u
p
.c
o
m
/p
c
p
/a
rtic
le
-a
b
s
tra
c
t/4
9
/6
/9
5
8
/1
8
Fig.2 PollencellsofW.floridaandV.sargentii.(a)ElectronmicrographofaW.floridaspermcell.Bothplastidsandmitochondriawere 12
observed in the cell. (b) Electron micrograph of an immunogold-labeled W. florida sperm cell. The labeling of DNA was abundant in 10
1
plastidsbutweakinmitochondria.(c)EpifluorescencemicrographsofaW.floridaspermcell.Arrowsindicateamitochondrion(stainedby b
DiOC6asanellipticalgranule)andthecorrespondingpositionintheDAPIstainingimage,andarrowheadsindicateafluorescentplastid y g
DNA granule (stained by DAPI) and the corresponding position in the DiOC6 staining image. (d) Electron micrograph of a mature ue
s
generativecellofV.sargentii.Plastidswerenotobservedinthecell.(e)ElectronmicrographofanearlygenerativecellofV.sargentii. t o
Plastidsappearedtobeapportionedtothevegetativecellatmitosis.(f)Electronmicrographofanimmunogold-labeledmaturegenerative n
0
cell of V. sargentii. The labeling of DNA was weak in mitochondria. gn, generative nucleus; m, mitochondrion; p, plastid; sn, sperm 3
nucleus;vn,vegetativenucleus. A
p
ril 2
0
1
9
machinery(rings)appearingattheconstrictionsites(Fig.3). fluorescence microscopy. In sperm cells of W. florida, each
Such structures imply plastid division (Mori et al. 2001, plastid appeared to contain a highly organized single
Kuroiwaetal.2002).Wethussuspectedthatplastidsinthe nucleoid (refer to Fig. 4). We did not detect separated
generativecellsofW.floridamightundergoactiveprolifera- nucleoids in any plastids in our study. This one-to-one
tionduringpollendevelopment.Totestthishypothesis,we correspondence, and the fact that DAPI-treated mitochon-
performed complete serial sectioning to determine the dria in sperm cells did not emit detectable fluorescence,
number of plastids in the earliest (lenticular) generative greatlyfacilitated quantification of plastids inthe cells.We
cells, just after the first pollen mitosis. In the five cells squashedthepollencellsintoathinlayersothatthenumbers
examined, newly formed generative cells contained an of fluorescent granules could be counted accurately by
averageof33.2(cid:3)5.2plastids(Table2).Wethendetermined slightlyadjustingthefocus(refertotheimageinFig.1).With
thenumberofplastidsinthespermcellswithDAPI-stained 10spermcellpairsexamined,onaverage70.7(cid:3)5.3plastids
962 Fluctuationofplastidgeneticsinangiosperm
amountoflabelingduringpollendevelopment.Theaverage
number of gold particles per plastid in the mature
sperm cells was 158% higher than in early cells (Fig. 4e).
This increased labeling was significant [Student’s t-test,
t¼2.834t (22)¼2.07]. Given the fact that the number
0.975
ofplastidsdoubledduringpollendevelopment,weconclude
that the conditions for paternal plastid contribution are
largely enhanced in the male gametophyte in W. florida.
Immunoelectron microscopy revealed weak labeling
(Fig.2b,f)andnofluorescentDNAsignals corresponding
D
tomitochondria(Fig.2c),suggestingthatthemitochondrial o
w
DNAinthemalereproductivecellsmaybedegradedduring n
lo
pollen development. Such degradation of mitochondrial a
d
e
DNA is a common trait that indicates maternal mitochon- d
drial inheritance. We also measured DNA labeling of fro
m
mitochondria at the early and mature stages of pollen h
development. In the early generative cell, uniform labeling ttps
with gold particles was observed in mitochondria of both ://a
c
W. florida and V. sargentii (Fig. 4a, c); this labeling was ad
e
distinct from the weak labeling observed in the mature m
Fig. 3 Dividing plastids in developing generative cells of W. ic
florida. Images were acquired from 110nm sections of the cells. sperm and generative cells (Figs. 2b, f and 4b, d). In .o
u
Arrowsindicatetheplastiddivisionrings. W. florida, examination of complete serial sections of p
.c
mitochondria from early generative and mature sperm om
cells revealed that the average number of gold particles /p
c
Table 2 Number of plastids in six early generative cells per mitochondrion in mature cells was 97% less than that p/a
and 10 mature sperm cell pairs of W. florida in early cells (Fig. 4e). Similarly, in V. sargentii, the aver- rtic
le
Early generative Mature sperm age labeling per mitochondrion was reduced by 98% in -a
b
cell cellsa (SC1/SC2) tdheegramdaattuiorne ocfelmlsito(Fchigo.nd4reia).l DTNheAseinretshueltmsadleemreopnrostdruacte- strac
33 65 (28/37) tive cells, ensuring maternal mitochondrial transmission t/49
25 76 (36/40) inthesespecies. /6/9
37 74 (35/39) 5
8
38 78 (36/42) /1
8
Occurrence of potential biparental plastid inheritance during 1
29 76 (35/41) 2
37 72 (31/41) late angiosperm phylogeny 101
The above results revealed the divergence of potential b
71 (37/34) y
plastid transmission patterns in traditional Caprifoliaceae. g
64 (37/27) u
e
66 (41/25) Based on previous studies, the genera Sambucus and st o
65 (29/36) Viburnum, which exhibit maternal transmission, along n 0
Mean(cid:3)SD 33.2(cid:3)5.2 70.7(cid:3)5.3 with Adoxa (the outgroup genus in this study), comprise a 3 A
monophyletic sister clade (recently named Adoxaceae) in p
SaTCh,espneurmmbceerll.of plastids in mature sperm cells was obtained theorderDipsacales(Belletal.2001,Donoghueetal.2003, ril 20
W. H. Zhang et al. 2003; Fig. 5). The remaining genera or 1
by counting the number of plastid DNA granules under an 9
epifluorescencemicroscope. families of this order, including Patrinia and Valeriana
(Valeriaceae), Dipsacus and Scabiosa (Dipsaceae), and
Morina (Morinaceae), all exhibit potential biparental
were counted in each pair of sperm cells (Table 2). This plastid inheritance (Q. Zhang et al. 2003; Fig. 5). The
confirmsthemultiplicationofplastidsinthemalereproduc- pattern of appearance of potential plastid inheritance
tivecellsduringpollendevelopment. implies that maternal and biparental modes may have
The duplication of plastid DNA was revealed by diverged in the early phylogeny of the order Dipsacales,
comparing the labeling of DNA per plastid between the because the genera, except for those in Adoxaceae, are
early generative and mature sperm cells. We examined monophyletic and all exhibit potential biparental plastid
complete serial sections of 12 plastids from both early and inheritance. Moreover, because mechanisms are developed
mature sperm cells and detected an increase in the total toenhancethestrengthofpaternalcontribution(seeplastid
Fluctuationofplastidgeneticsinangiosperm 963
(a) (e)
W. florida W. florida
75
n=15
n 480
drio 50 n=12 d
on sti
h a
mitoc 25 n=50 360 per pl
(b) of particles per 75 n=42 V. sargentii n=12 240 ber of particles Dow
mber 50 120 Num nload
u e
N d
25 n=42 fro
m
h
EGC MGC/MSC EGC MSC ttps
://a
c
(c) (d) a
d
e
m
ic
.o
u
p
.c
o
m
/p
c
p
/a
Fig. 4 Changes in the amounts of mitochondrial and plastid DNA labeling during pollen development. (a) Electron micrograph with rtic
immunogoldlabelingofsequentialsectionsofanearlygenerativecellofW.florida.Bothplastidsandmitochondriawerestronglylabeled le-a
inthecellsatthisstage.(b)Electronmicrographofserialsectionsofanimmunogold-labeledW.floridaspermcell.Plastidsinthecells b
s
werestronglylabeled,butlabelingofmitochondriawasdecreased.(c)Electronmicrographofanimmunogold-labeledearlygenerative tra
cellofV.sargentii.Mitochondriainthecellwerestronglylabeled.(d)Electronmicrographofserialsectionsofanimmunogold-labeled ct/4
maturegenerativecellofV.sargentii.Goldlabelingofmitochondriainthematurecellwasdecreased.(e)QuantitativechangeinDNA 9
/6
labelingpermitochondrionandplastidduringpollendevelopment.Datawerecollectedfromcompleteserialsectionsofmitochondriaand /9
plastids.Graycolumnsshowthenumberofgoldparticlespermitochondrionorplastid,asindicatedinthefigurelabels.Blackcolumns 58
showthebackgroundlevelofgoldparticlesinequivalentareasofthesections.gn,generativenucleus;m,mitochondrion;p,plastid;EGC, /1
8
earlygenerativecell;MGC,maturegenerativecell;MSC,maturespermcell.ErrorbarsindicatetheSD. 12
1
0
1
b
y
andplastidDNAduplicationinFigs.3and4e,andTable2) angiosperm genera (Fig. 6). Of these, 81.1% (167/206) g
u
in the species with potential biparental inheritance, we showed maternal plastid inheritance, and 18.9% (39/206) es
furtherproposethatbiparentalplastidinheritancemaybea showed potential biparental inheritance. Such rates are t o
n
trait that has been acquired upon maternal transmission consistent with the natural appearance of maternal and 03
A
(discussed below). potential biparental plastid transmission in angiosperms. p
We therefore performed an extended phylogenetic Becausetheaimofthisanalysiswastolearnhowandwhen ril 2
0
analysis using angiosperm species with a known potential maternal and biparental plastid inheritance evolved during 1
9
mode of plastid inheritance. Using data from previous angiosperm phylogeny, we first examined the mode of
studies, we surveyed4600 such species and confirmed that plastidtransmissionintheearliestangiosperms.Theearliest
the major clades of angiosperm phylogeny are well repre- angiosperms are Amborellaceae, Nymphaeaceae and a
sented(CorriveauandColeman1988,Q.Zhangetal.2003). clade that contains Illiciaceae, Schisandraceae, Trimenia-
As a framework, we used the most recent phylogenetic ceae and Austrobaileyaceae (Qiu et al. 1999, Soltis et al.
scheme suggested by the Angiosperm Phylogeny Group 2000). Our analysis included information on Nymphaea
(Soltisetal.2000,AngiospermPhylogenyGroup2003).To (Nymphaeaceae) and Illicium (Illiciaceae), with maternal
matchtheframeworkbest,weomittedspecieswithuncertain plastid transmission (Fig. 6). In addition, our phylogenetic
phylogenicpositions. tree also suggests that maternal plastid inheritance should
The phylogenetic tree that we established displays occur in the established basal branches of angiosperms
information for potential plastid inheritance in 206 such as Nelumbo, Ceratophyllum, Magnolia, Liriodendron,
964 Fluctuationofplastidgeneticsinangiosperm
Potential biparental Patrinia heterophylla Valerianaceae s II
Valeriana officinalis d
DSMcioparsbinaioacus nase atpssacplheeinlrioesiinsdseiss DMiiprisnaaccaecaeeae aternal parental Caprifoliaceae euasteri
DKoiplkewltait zfilao raibmuanbdialia Linnaeaceae ntial m ntial bi ds I
ALTribnioenslaitaee uabm ifblo oprriaenanlaistifidum Pote Pote erids euasteri
Symphoricarpos sinensis ast D
Lonicera maackii Caprifoliaceae ow
n
Leycesteria formosa lo
a
Heptacodium miconioides d
e
WSVaibemuigrbenuluacm ufls os rwaidrilgalieanmtisiii ADdieorxivailclaecaeeae cots urosids II d from h
Fig.P5otenPtiahl ymloagteernnaeltic relatioAndoshxaip msosacmhaotenlgliangaenera in the order ore eudi ds e ttps://ac
Dseiqpusaecnacleesa.naTlhyesisborafnpclahsintidg gpeantteesrnrepoofrttehdeptrreeveiouwsalys (bBaeslledetoanl. c rosi sids I adem
2001, Donoghue et al. 2003, W. H. Zhang et al. 2003). Genera euro ic.o
with potential biparental plastid transmission are shown in gray, up
and those with maternal transmission are in black. The potential .co
m
biparental classification for Patrinia heterophylla, Valeriana offici-
/p
nalis, Dipsacus asperoides, Scabiosa tschiliensis and Morina c
p
nepalensis was taken from our previous study (Q. Zhang et al. /a
2003). Shading indicates the species of traditional Caprifoliaceae rtic
examined in this study, which were recently reclassified into le-a
Linnaeaceae,Caprifoliaceae,Diervillaceae,andAdoxaceae. eudicots bstract/4
9
Laurus, Chimonanthus, Aristolochia and Chloranthus /6
(Fig. 6). The consistent appearance of maternal transmis- /95
8
sion in these lineages implies that maternal plastid /1
8
ibnihpearrietnatnaclepilsastthide ainnhceersittraanlceconisdidtieorniveadndfrosumggemstastetrhnaatl cots elinids 12101
inheritance (Fig. 6). Moreover, phylogenetic analysis o m b
n m y
showed a distribution of potential biparental plastid ms mo co gu
inheritance throughout the taxa, implying apparently er es
polyphyletic occurrence of the trait in angiosperms. osp t on
gi 0
Discussion an agnoliids 3 April 2
m 0
Occurrence of potential biparental plastid inheritance in the 1
9
early phylogeny of Dipsacales Fig. 6 Phylogenetic distribution of 206 angiosperm genera with
known potential modes of plastid transmission. The branching
In this study, we demonstrated the widespread
patterns are based on the results of the Angiosperm Phylogeny
occurrence of potential biparental plastid inheritance in
Group (Soltis et al. 2000, Angiosperm Phylogeny Group 2003).
traditional Caprifoliaceae. This traditional family was
Genera with potential biparental plastid inheritance are shown in
recently classified into four independent families: Adox- red,andthosewithmaternalinheritanceareinblack.Branchesof
aceae,Caprifoliaceae,DiervillaceaeandLinnaeaceae,based Nymphaea and Illicium, the earliest known angiosperms, are
on intensive analysis of gene similarity (Bell et al. 2001, indicated by black dots, and those of Buxus, Nelumbo,
Ceratophyllum, Magnolia, Liriodendron, Laurus, Chimonanthus,
Donoghue et al. 2003, W. H. Zhang et al. 2003). Of these
Aristolochia and Chloranthus, the established basal angiosperm
families, Caprifoliaceae, Diervillaceae and Linnaeaceae
group,areindicatedwithasterisks(seeSupplementarymaterialfor
comprise genera that all exhibit potential biparental detailsofthegenusandrepresentativespecies).Shadingindicates
plastid inheritance (Figs. 1, 5, Table 1). This consistent thepositionoftraditionalCaprifoliaceae.
Fluctuationofplastidgeneticsinangiosperm 965
occurrence of potential biparental inheritance throughout DNA in the male reproductive cells of Pelargonium zonale,
related families is unusual, because potential biparental Medicago sativa, Rhododendron mucronatum and Petunia
inheritance usually occurs only in some genera within hybrida. These species are all genetically established as
certain families (Corriveau and Coleman 1988, Q. Zhang exhibiting biparental plastid inheritance. The same phe-
et al. 2003). Furthermore, the consistent occurrence of nomenonwasthenreportedinSyringapekinensis(Liuetal.
potential biparental inheritance has emerged in other 2004a) and Wisteria sinensis (Hu et al. 2005), species that
families of Dipsacales: Dipsacaceae, Morinaceae and exhibitpotentialbiparentalplastidinheritance.Inaddition,
Valerianaceae (see our previous report: Q. Zhang et al. quantitative cytology revealed an aggressive increase
2003). Thus, except for the Adoxaceae, which exhibit in DNA-containing plastids in the generative cells of
maternal inheritance, the remaining genera in Dipsacales Chlorophytum comosum, a species genetically shown to
D
all exhibit potential biparental inheritance (Figs. 1, 5, exhibit biparental plastid inheritance (Liu et al. 2004b). o
w
Table 1). Interestingly, we found that this divergence in Togetherwiththeresultsofourstudy,itappearsthatinall n
lo
the mode of potential plastid inheritance perfectly matches speciesexaminedsofar,activeenhancementofthepaternal ad
e
the phylogeny of Dipsacales, in which the Adoxaceae contribution to inheritance is a trait that occurs in all d
are established as a small monophyletic clade and the species exhibiting biparental or potential biparental plastid from
remaining families constitute a large monophyletic clade inheritance. This implies that the conversion of plastid h
(Fig. 5). We therefore presume that the ancestor of inheritance from the maternal to the biparental mode ttps
Dipsacales may be a phylogenic turning point at which a may be a major source of the occurrence of biparental ://a
c
switch between maternal and biparental plastid inheritance inheritance in angiosperms. ad
e
occurred. To delineate a general pattern for the fluctuation in m
ic
A previous study suggested that maternal and bipa- plastidinheritanceinangiospermevolution,weconducteda .o
u
rental modes of plastid genetics had inverted and reverted meticulous phylogenetic analysis by incorporating as many p.c
throughout angiosperm phylogeny (Birky 1995). This speciesaspossiblewith known(potential)modesofplastid om
implies that maternal plastid inheritance in angiosperms inheritance. In contrast to a previous study (Birky 1995), /pc
p
maybeconvertedtobiparentalinheritanceand,inthecase our examination included Illicium verum and Nymphaea /a
of inversion, biparental inheritance may be converted to tuberosa, the earliest established angiosperms (Qiu et al. rtic
le
maternal inheritance. The identification of the switching 1999, Soltis et al. 2000) and a group of species that are -a
b
ptinhohuinesrtisct,rainatitcceawlfhlufiocchrtuutahnteedsemrinsotdaaenndgoiinfogspplhaersomtwidptihhnyehleomrgitoeandnyec.eoHfaoltpwelraesvs,teirids, kSinnuhopewprilnteamnteconetiabnreythbeFsaiesga.slp1ebcfireoasrnicmshpepeslcieieossfthdtaehtteathileas)na.gniTgoihsopeseprmemramstesr(naseraeel stract/49
because plastid inheritance was usually examined with the rootedinmaternalplastidgenetics(Fig.6).Theuniparental /6/9
5
genus of isolated families, the previous study failed to plastid inheritance found in the unicellular green alga 8/1
identify such points. In the present study, we identified the 8
Chlamydomonas (Kuroiwa et al. 1982, Nishimura et al. 1
divergencebyserialinspectionoftraditionalCaprifoliaceae, 1999) and gymnosperms (either maternal or paternal in 210
and our results appear to support the case that potential 1
gymnosperms, see Mogensen, 1996), which evolved much b
biparental inheritance seems to occur through maternal earlier than the angiosperms, supports the idea that y g
u
inheritance. The cytological examination revealed active ancestors of angiosperms had uniparental (maternal) es
duplication of plastids and plastid DNA in the generative inheritance. This was distinct from the previous study, in t on
cells of W. florida, a representative species for potential which, perhaps owing to insufficient available information 03
biparental inheritance (Figs. 3, 4). This demonstrates that A
on plastid inheritance in ancient angiosperm species, the p
the paternal contribution is enhanced by cellular mechan- mode of plastid inheritance in the ancestral angiosperms ril 2
isms that are not seen in species exhibiting maternal 0
was equivocal (Birky 1995). Based on both cytological 1
9
inheritance (for degeneration of plastids in the male
evidenceandourphylogeneticexamination,wesuggestthat
reproductive cell, see Hagemann and Schro¨der 1989). The
angiospermspeciesexhibitingbiparentalplastidinheritance
development of mechanisms for paternal contribution
may have arisen directly from their ancestors that had
supports the idea that potential biparental plastid inheri-
maternalinheritance inangiosperm phylogenywithout any
tance in Dipsacales is derived from maternal inheritance.
reversion.
Why did the previous study (Birky 1995) suggest that
Unilateral occurrence of potential biparental plastid plastid inheritance may have shifted frequently between
inheritance in angiosperms maternal and biparental modes during angiosperm phylog-
Active enhancement of the paternal contribution to eny? We presume that this difference in results may be due
plastid inheritance was first reported by Nagata et al. to the classification of angiosperm species as having a
(1999). Their study revealed selective duplication of plastid maternal or biparental mode. As a matter of fact, plastid
966 Fluctuationofplastidgeneticsinangiosperm
inheritance is neither strictly maternal nor biparental. In Maxim.,S.williamsiiHance,S.sinensisRehd.,V.sargentiiKoehne
species that exhibit maternal transmission, Nicotiana and W. florida (Bunge) A. DC], the Xiaolongmen Forest Park,
Mentougou, Beijing (A. moschatellina Linn.), the Hangzhou
tabacumforexample,paternalplastidsleaktotheoffspring
Botanical Garden, Zhejiang (H. miconioides Rehd.), the
with frequencies of 0.07 and 2.5% in interspecific and
Jiuzhaigou Valley, Sichuan (D. floribunda Maxim. and
intraspecific crosses, respectively (Medgyesy et al. 1986). T. pinnatifidum Maxim.), the Kunming Botanical Garden,
Such a low rate of paternal organelle leakage, termed Chinese Academy of Sciences, Kunming, Yunnan (L. formosa
‘occasional biparental transmission’ (Smith 1988, Yu and Wall.) and Changbai Mountain in Erdaobaihe, Jilin (L. borealis
Linn).Pollengrainsweregatheredfromtheflowersbeforeuse.
Russell 1994), occurs ubiquitously in plants known to
exhibit maternal inheritance (e.g. Cornu and Dulieu 1988,
Epifluorescencemicroscopy
SchmitzandKowallik1986,Sewelletal.1993).Inthestudy
Inspection of plastid DNA with epifluorescence microscopy
D
of Birky (1995), a clade containing Antirrhinum, Borago, was performed according to Kuroiwa and Suzuki (1980). Mature o
w
Petunia, Lycopersicon and Nicotiana gives the example of pollengrainswereplacedonaglassslideandimmersedinadropof n
lo
the ‘inversion’ of plastid inheritance from biparental to TAN buffer (Nemoto et al. 1988) supplemented with 3% a
d
maternal mode. With the exception of Lycopersicon, glutaraldehyde and 1mgml(cid:2)1 DAPI. The pollen grains were ed
paternal plastid leakage is detected in the other genera. It squashed on the slide. After 5min of fixation and staining, the fro
samples were examined under an epifluorescence microscope m
seems that a maternal genus (Lycopersicon) derives from (Olympus, Tokyo, Japan). Photomicrographs of the cells were h
biparental genera (Antirrhinum, Borago, Petunia and captured with a cooled CCD camera (Spot-RT; Diagnostic ttps
Nicotiana). We disagree with this explanation because Instruments, Sterling Heights, MI, USA) attached to the ://a
(i) paternal plastid leakage is clearly different from microscope. ca
d
biparentalinheritanceand(ii)leakage-freematernalinheri- ThedoublestainingofpollencellswithDAPIandDiOC6was em
tance in Lycopersicon may need to be retested, because a bfiaxseeddinon3%theglumteatrhaolddeshoyfdeNiangcaatcaoedtylaalt.e(1b9u9ff9e)r.(PpoHlle7n.4g)rfaoirn2s4whearet ic.ou
species with strict maternal inheritance has not been 48C,dehydratedthroughanethanolseries,andthenembeddedin p.c
reported so far. To distinguish between paternal leakage Technovit7100resin(KulzerandCo.,Wehrheim,Germany).The om
and biparental inheritance, we adopted potential inheri- sampleswerecutinto500nmthicksectionsonanUltracutMicro- /p
c
tlienaankctaeh,giesaansctdeuldaluyclt,aivreantprdlaaistotiutdhradturpeclsliuecalatrtiloyynie,rlefdpoeordrtthsethtcerlaacsuesinfiiplcalaattesirtoiandl eDtwotehAmraePenIso(tLlaieiannincedaTd,AdwViNsiittehinllbn1euda0f,0wfAemaru.tgesmtrTr,iolaa(cid:2)n)1pdaDrnteihdvOeedCnnrt6ifeuidfnratoehdtneihnrcagson,tvaoe1ilnr,msewldigapwmssh.iletT(cid:2)hd1h1wenmis-tephgcrtm5oi0opl%(cid:2)nys1l p/article-a
occurrenceofbiparentalplastidinheritanceinangiosperms. gallate in 50% glycerol was added to the samples before the bs
epifluorescence microscopic examination. Photomicrographs were trac
Possible evolutionary pressure for biparental inheritance capturedwiththecooledCCDcameradescribedabove. t/4
9
throuIgfhbipmaarteenrtnaallpilnashteidritgaennceet,icosnien managyioqspueersmtiosnocwcuhryreidt Electronmicroscopy /6/958
For transmission electron microscopy, pollen grains were /1
occursinthelatephylogeny.Birky(1995)predictedpossible fixedin3%glutaraldehydeincacodylatebuffer(pH7.4)for24hat 81
traits, including nuclear–plastid incompatibility, that may 48C,andthenovernightin1%osmiumtetroxideat48C.Thefixed 21
0
have driven the shift of plastid genetics. We note the fact pollen grains were dehydrated through an alcohol series and 1
b
that plants with deficient chlorophyll pigmentation caused embedded in Spurr’s resin. Ultrathin sections were collected in y g
by defective plastids could be effectively recovered by copper grids with a single slot, stained in 1% uranyl acetate and ue
lead citrate, and examined under an electron microscope (JEOL, s
pollination with wild-type pollen. In Oenothera and Pisum, Tokyo, Japan). The electron photomicrographs of the cells were t o
n
it has been demonstrated that wild-type plastids are captured with a cooled CCD unit (XR40; Advanced Microscopy 0
3
inherited by F1 progeny from the paternal lineage in Techniques,Danvers,MA,USA)attachedtothemicroscope. Ap
vtyaprieopuhsenporotyppoertoiofnpsl,anatnsd(CthhieuseanpdlaSsteiadrss1re9s9t3o,reBotghdeawnoilvda- DNAImwmasunboaesleedctroonntmheicrmoestchoopdysfoofr JtohhensdoentecatniodnRoofsecnebllauulamr ril 20
1
2007). Owing to the fact that transmission of plastids (1990). Pollen grains were fixed with glutaraldehyde as described 9
above, but with the post-fixation step omitted, and embedded in
through the paternal lineage acts to rescue plants with
LR White resin (Sigma-Aldrich Chemie, Steinheim, Germany).
nuclear–plastidincompatibility,wepresumethatbiparental Continuoussectionswerecollectedinnickelgridswithasingleslot.
inheritance may have benefited the speciogenesis of species The grids were incubated with a mouse monoclonal antibody
with a defective mutation in the plastid genome. that recognizes single- and double-stranded DNA (Boehringer
Mannheim, Mannheim, Germany). After washing, the grids were
incubated with a goat anti-mouse IgM conjugated to 10nm
Materials and Methods
colloidalgold(BritishBioCellInternational,Cardiff,UK).Finally,
the samples were stained with 1% uranyl acetate and examined
Plantmaterials under the electron microscope. For a negative control, sections
We collected fresh flowers from plants grown in the Beijing were pre-treated with DNase and processed as above. The free
Botanical Garden, Institute of Botany, Chinese Academy of localization of immunogold particles was routinely confirmed on
Sciences,Beijing[A.bifloraTurcz.,K.amabilisGraebn.,L.maackii thesecontrolsections.
Fluctuationofplastidgeneticsinangiosperm 967
Phylogeneticanalysis Correns, C. (1909) Vererbungsversuche mit blass(gelb)gru¨nen und bunt-
Arecentlyestablishedphylogeneticscheme(Soltisetal.2000. bla¨ttrigensippenbeiMirabilisjalapa,UrticapiluliferaundLunariaannua.
Angiosperm Phylogeny Group 2003) was used as our framework Z.Indukt.Abstammungs-Vererbungsl.1:291–329.
Corriveau, J.L. and Coleman, A.W. (1988) Rapid screening method to
for the phylogenetic analysis. A literature survey yielded 4600
detect potential biparental inheritance of plastid DNA and results for
angiospermspecieswithknownmodesofplastidinheritance;most
over200angiosperms.Amer.J.Bot.75:1443–1458.
dataweretakenfrompreviouswide-scaleexaminations(Corriveau
Donoghue,M.J.,Bell,C.D.andWinkworth,R.C.(2003)Theevolutionof
and Coleman 1988, Q. Zhang et al. 2003). Data for potential reproductivecharactersinDipsacales.Int.J.PlantSci.164:s453–464.
biparental transmission in Jasminum and Ligustrum were from Hagemann, R. and Schro¨der, M.B. (1989) The cytological basis of the
separatestudies(Sodmergenetal.1998,Liuetal.2004a).Datafor plastidinheritanceinangiosperms.Protoplasma152:57–64.
maternalplastidtransmissioninLaurus,Chloranthus,Illicium,Ilex, Hu, Y.F., Zhang, Q. and Sodmergen, (2005) Potential cytoplasmic
BenthamiaandSpinacia,andbiparentaltransmissioninSymphor- inheritance in Wisteria sinensis and Robinia pseudoacacia
icarposwerebasedonourunpublishedresults.Weexcludedgenera (Leguminosae).PlantCellPhysiol.46:1029–1035.
Johnson, K.A. and Rosenbaum, J.E. (1990) The basal body of D
with uncertain relationships to those determined in the phyloge- o
Chlamydomonasreinhardtiidoesnotcontainimmunologicallydetectable w
netic scheme. Because the mode of plastid inheritance does not n
DNA.Cell62:615–619. lo
appear to change within a genus (Corriveau and Coleman 1988, Kuroiwa,H.,Mori,T.,Takahara,M.,Miyagishima,S.andKuroiwa,T. ad
Q.Zhangetal.2003),weusedonespeciestorepresenteachgenus. (2002) Chloroplast division machinery as revealed by immunofluores- ed
Theapproximatetimingfortheappearanceofangiospermgenera cenceandelectronmicroscopy.Planta215:185–190. fro
wastakenfromWikstro¨metal.(2001). Kuroiwa, T. (1991) The replication, differentiation, and inheritance of m
plastidswithemphasisontheconceptoforganellenuclei.Int.Rev.Cytol. h
128:1–62. ttp
SupplSeumpepnlteamryenmtaarteyrimalaterial mentioned in the article is avail- KuErpoiifwluao,reTsc.,entKmawicaronsoc,opSic.,evNidiesnhcibeafyoarshmi,ateSr.naalnindherSiataton,ceCo.fc(h1l9o8ro2-) s://ac
a
able to online subscribers at the journal website www.pcp. plastDNA.Nature198:481–483. d
e
oxfordjournals.org. Kuroiwa, T. and Suzuki, T. (1980) An improved method for the m
demonstration of the in situ chloroplast nuclei in higher plants. Cell ic
.o
Struct.Funct.5:195–197. u
Funding Liu,Y.,Cui,H.X.,Zhang,Q.andSodmergen (2004a)Divergentpotentials p.c
for cytoplasmic inheritance within the genus Syringa. a new trait om
The National Basic Research Program of China (973 Liua,ssYo.c,iZatheadnwg,itQh.,spHeuc,ioYg.eFn.easinsd.PSloadnmtePrhgyesnio(l.2010346b:)2H76e2t–er2o7g7e0n.eouspollen /pcp
Program, No. 2007CB108700); the National Natural in Chlorophytum comosum, a species with a unique mode of plastid /a
Science Foundation of China for a Creative Research inheritance intermediate between the maternal and biparental modes. rtic
Group program (No. 30421004) and a Key Program (No. PlantPhysiol.135:193–200. le-a
Medgyesy, P., Pay, A. and Marton, L. (1986) Transmission of paternal b
30430040). chloroplastsinNicotiana.Mol.Gen.Genet.204:195–198. stra
Miyamura,S.,Kuroiwa,T.andNagata,T.(1987)Disappearanceofplastid c
andmitochondrialnucleoidsduringtheformationofgenerativecellsof t/4
Acknowledgments higher plants revealed by fluorescence microscopy. Protoplasma 141: 9/6
149–159. /9
5
Mogensen,H.L.(1988)Exclusionofmalemitochondriaandplastidsduring 8
We thank Professor Hongya Gu of Peking University for /1
syngamyinbarleyasabasisformaternalinheritance.Proc.NatlAcad. 8
valuablediscussionsonangiospermphylogeny. 1
Sci.USA85:2594–2597. 2
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Mogensen,H.L.(1996)Thehowsandwhysofcytoplasmicinheritancein 0
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