Regulation of photosynthesis in plants under abiotic stress

306 Pages·2014·12.96 MB·English

Regulation of Photosynthesis in plants under abiotic
stress
A thesis submitted to the University of Manchester for the
degree of PhD in the Faculty of Life Sciences
2014
Sashila Abeykoon Walawwe
1
Table of contents
List of Figures 5
List of Tables 9
Abbreviations 10
Abstract 12
Declaration 13
Copyright Statement 13
Acknowledgements 14
Chapter 1- General Introduction 15
1.1. Introduction 16
1.2. Photosynthesis 18
1.2.1. Light capture and electron transport chain 18
1.2.2. Cyclic electron transport 31
1.2.3. The Calvin-Benson-Bassham cycle 39
1.3. Effects of abiotic or environmental stress on plants 43
1.3.1. Salt stress 43
1.3.1.1. Effects of salt stress on plants 45
1) Effects of salt on plant growth 45
2) Effects of salt on photosynthesis 46
3) Effects of salt on water relations and ion balance in plants 47
4) Effects of salt on photosynthetic pigments, proteins and lipid 48
composition
5) Effects of salt on leaf anatomy and the structure of chloroplast 49
6) Effects of salt on the nitrate and malate metabolism 50
1.3.1.2. Sensing and signal transduction in salt stress tolerance 51
1.3.1.3. Transcriptomics and proteomics of salt tolerance 55
1.3.1.4. Salt tolerance mechanisms in plants 59
1) Ion regulation and compartmentalization 59
2) Accumulation of compatible solutes 64
3) Involvement of the antioxidant enzymes 65
4) Involvement of plant hormones 67
1.3.1.5. Effects of salt stress on other photosynthetic organisms 69
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1) Cyanobacteria 69
2) Algae 73
1.3.2. Drought stress 75
1.3.3. Heat stress 76
1.3.4. Low temperature stress 77
1.4. Effects of Environmental stress on the electron transport of photosynthesis 80
1.4.1. Effects on energy use in photosynthesis 81
1.4.1.1. Reactive oxygen species (ROS) formation 82

1.4.2. Effects on components of the electron transport 85
1.5. Regulation of electron transport chain of photosynthesis under stress conditions 89
1.5.1. State-transitions (qT) 89
1.5.2. High-energy state Quenching (qE) 92
1.5.3. Other electron transport pathways involved in regulatory process 98
1.5.3.1. Mehler Reaction 98
1.5.3.2. Chlororespiration 100
1.6. Involvement of Plastid terminal oxidase (PTOX) in alternative electron transport 103
in the electron transport chain of Thellungiella salsuginea
1.7. Aims and Objectives 110
Chapter 2- Effect of salt stress on the regulation of photosynthesis in barley 112
(Hordeum vulgare L.)
Preface 113
2.1. Abstract 114
2.2. Introduction 115
2.3. Materials and Methods 119
2.4. Results 130
2.5. Discussion 140
Chapter 3- Physiological evaluation of salinity stress in two rice varieties from Sri Lanka 149
Preface 150
3.1. Abstract 151
3.2. Introduction 152
3.3. Materials and Methods 157
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3.4. Results 169
3.5. Discussion 187
Chapter 4- Regulation of photosynthesis in Thellungiella salsuginea under abiotic stress 197

Preface 198
4.1. Abstract 199
4.2. Introduction 200
4.3. Materials and Methods 206
4.4. Results 215
4.5. Discussion 231
Chapter 5- General Discussion 239
Bibliography 247
Word Count: 59755
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List of Figures
Chapter 1- Introduction
Figure 1.1. Schematic model of the major protein complexes involved in electron transport 20
chain in photosynthesis
Figure 1.2. Schematic model representing the proteins of light harvesting complex II 23
(LHCII) and reaction centre core (RCII) of photosystem II (PSII)
Figure 1.3. The model of Q cycle representing the electron and proton transport in the 26
cytochrome b f
6
Figure 1.4. Schematic model representing the proteins of light harvesting complex I (LHCI) 28
and reaction centre core (RCI) of photosystem I (PSI)
Figure 1.5. Schematic model representing the chloroplast ATP synthase 30
Figure 1.6. Possible pathways of cyclic electron transport around PSI 38
Figure 1.7. A diagram representing the major steps in the Calvin cycle or the light-independent 42
reactions
Figure 1.8. Cellular Na+ transport mechanisms and important components of the salt 54
stress responses in plant root cells
Figure 1.9. Regulation of electron transport through qE 97
Chapter 2
Figure 2.1. Far-red light induced signal giving the 100% of P700 122
Figure 2.2. Typical fluorescence signal showing all the reference points 123
Figure 2.3. P700 oxidation of which is induced by the actinic light was measured during 126
a 100 milliseconds period of darkness
Figure 2.4. The relative concentration of 'active' PSI centres (centres that can be oxidized by 127
light and are then rapidly re-reduced during a period of darkness)
Figure 2.5. The first leaf of barley plant showing the section of approximately 2.1 cm2 128

(length 3 cm x width 0.7 cm between 4 cm and 7 cm from the leaf tip
of each leaf) area
Figure 2.6. Gas exchange parameters of barley plants subjected to varying degrees 132
of salinity
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Figure 2.7. Maximum quantum yield (Fv/Fm) of control and salt-treated barley plants 133
Figure 2.8. The effect of salt treatment on the efficiency of PSII (ΦPSII), relative 135
electron transport of PSII (PSII ETR) and non-photochemical quenching (NPQ)
of barley plants
Figure 2.9. The effect of salt treatment on redox state of P700, relative proportion of the 138
active PSI centres, rate constant for P700 reduction and electron transport
rate of PSI (PSI ETR) of barley plants
Figure 2.10. The effect of salt treatment on the leaf chlorophyll content per leaf area and 139
chlorophyll a/b ratio in barley

Chapter 3
Figure 3.1. Far-red light induced signal giving 100% of P700 161
Figure 3.2. Typical fluorescence signal showing all the reference points 162
Figure 3.3. P700 oxidation induced by the actinic light was measured during a 164
100 milliseconds period of darkness
Figure 3.4. The relative concentration of 'active' PSI centres (centres that can be oxidized by 165
light and are then rapidly re-reduced during a period of darkness)
Figure 3.5. Fluorescence signal showing the relaxation kinetics 167
Figure 3.6. 34 days old At-354 and Bg-352 control and salt treated plants at the early 170
vegetative stage
Figure 3.7. Change in leaf area of two rice varieties At-354 and Bg-352 at the early 171
vegetative stage and at the flowering stage when exposed to 50 and 100 mM
of NaCl
Figure 3.8. The effect of salinity on leaf chlorophyll content per leaf area and chlorophyll 173
a/b ratio in two varieties of rice, At-354 and Bg-352
Figure 3.9. Gas exchange parameters measured in rice plants at the early vegetative stage 175
and the flowering stage of Bg-352 and At-354 exposed to: 0, 50 and 100 mM
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of NaCl
Figure 3.10. CO assimilation rate (A) as a function of internal CO concentration (Ci) in 176
2 2
plants at the tillering stage and flowering stage of Bg-352 and At-354 exposed
to: 0, 50 and 100 mM of NaCl
Figure 3.11. Maximum quantum yield (Fv/Fm) of salt stressed (50 or 100 mM) and control 177
plants at early vegetative stage and at flowering stage of At-354 and Bg-352
Figure 3.12. Photochemical efficiency (ΦPSII) and relative linear electron transport rate of 179
PSII (PSII ETR) plants at the early vegetative stage and the flowering stage of
Bg-352 and At-354 exposed to: 0, 50 and 100 mM of NaCl
Figure 3.13. Non Photochemical Quenching (NPQ) plants at the early vegetative stage and 181
the flowering stage of Bg-352 and At-354 exposed to: 0, 50 and 100 mM of NaCl
Figure 3.14. Chlorophyll fluorescence relaxation kinetics of control and salt treated plants at 182
the flowering stage recorded using the PAM 101 fluorometer.
Figure 3.15. Redox state of P700 and the proportion of 'active' PSI centres of two rice 184
varieties subjected to different salt concentrations plants at the early vegetative
stage and the flowering stage
Figure 3.16. The rate constant of P700 reduction and PSI electron transport rate (PSI ETR) of 186
plants at the early vegetative stage and the flowering stage of Bg-352 and At-354
exposed to: 0, 50 and 100 mM of NaCl.

Chapter 4
Figure 4.1. Images showing the physical changes of leaves of 7-week old T. salsuginea 216
when exposed to stresses.
Figure 4.2. Immunoblots and relative band intensity of PTOX, cytochrome f (Cyt f) and 218
PsbA from control, salt-treated, droughted and plants exposed to different growth
7
irradiance
Figure 4.3. PTOX gene expression along with actin and the relative expression level of 220
PTOX mRNA in control and salt-treated plants.
Figure 4.4. Change in the efficiency of PSII (ΦPSII) measured in control and stressed 222
plants at the different light intensities and CO concentration of >1200 μL L-1
2
Figure 4.5. Change in the electron transport rate of PSII (ETR of PSII) measured in control 223
plants and stressed plants at the different light intensities and CO concentration
2
of >1200 μLL-1
Figure 4.6. Blue-native PAGE showing the separated complexes of isolated thylakoids of T. 225
salsuginea
Figure 4.7. PTOX genomic sequence of T. salsuginea including exons, introns and 229
untranslated regions (UTRs) coding sequence of PTOX which indicates
the annealing sites of primers used in rt-PCR analysis.
Figure 4.8. The schematic representation of the genomic structure of PTOX contains exons, 230
introns and transcription start site (ATG) and stop codon (TAA)
Chapter 5- General Discussion
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List of Tables
Chapter 1
Table 1.1. Functional groups of genes/proteins induce under salt stress 56
Table 1.2. Selective examples of genes/proteins induced by salt stress 57
Table 1.3. Reactions of the Mehler or water-water cycle 99
Chapter 3
Table 3.1. Fast and slow-relaxation components of NPQ (NPQ and NPQ , respectively) in 181
F S
two varieties of rice, At-354 and Bg-352 at the early vegetative and flowering
stages subjected to 0, 50 and 100 mM NaCl
Chapter 4
Table 4.1. PTOX and actin primers used in rt-PCR 214
Table 4.2. Proteins identified by the mass spectrometry. BN-PAGE separated protein 226
complexes of the thylakoid membranes isolated from T. salsuginea plants
exposed to salt, drought and different irradiances
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Abbreviations
A assimilation rate
ADP adenosine diphosphate
ATP adenosine triphosphate
ATPase ATP synthase
CET cyclic electron transport
Car carotenoid
Chl chlorophyll
3Chl* triplet excited state of chlorophyll
Ci internal CO concentration
2
Cyt b f cyctochrome b f complex
6 6
Cyt f cyctochrome f
ETR electron transport rate
ETC electron transport chain
Fd ferredoxin
FQR ferredoxin-plastoquinone oxidoreductase
FNR ferredoxin: NADP reductase
Fo initial fluorescence level (obtained when QA is maximally oxidised)
Fm maximum chlorophyll fluorescence level (obtained when QA is maximally reduced)
Ft actual fluorescence intensity at any time
FR far-red
gs stomatal conductance
k pseudo-first order rate constant for the reduction of oxidised P700
LED light emitter diode
LHCI light harvesting complex I
LHCII light harvesting complex II
NADP oxidized nicotinamide adenine dinucleotide phosphate
NADPH reduced nicotinamide adenine dinucleotide phosphate
NPQ non-photochemical quenching
P680 primary electron donor of PSII
P680+ oxidised primary electron donor of PSII
P700 primary electron donor of PSI
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