Chloroplast function and ion regulation in plants growing on saline soils: lessons from halophytes
Date
2017
Authors
Bose, J.
Munns, R.
Shabala, S.
Gilliham, M.
Pogson, B.
Tyerman, S.
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Journal article
Citation
Journal of Experimental Botany, 2017; 68(12):3129-3143
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Jayakumar Bose, Rana Munns, Sergey Shabala, Matthew Gilliham, Barry Pogson and Stephen D. Tyerman
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Abstract
Salt stress impacts multiple aspects of plant metabolism and physiology. For instance it inhibits photosynthesis through stomatal limitation, causes excessive accumulation of sodium and chloride in chloroplasts, and disturbs chloroplast potassium homeostasis. Most research on salt stress has focused primarily on cytosolic ion homeostasis with few studies of how salt stress affects chloroplast ion homeostasis. This review asks the question whether membrane-transport processes and ionic relations are differentially regulated between glycophyte and halophyte chloroplasts and whether this contributes to the superior salt tolerance of halophytes. The available literature indicates that halophytes can overcome stomatal limitation by switching to CO2 concentrating mechanisms and increasing the number of chloroplasts per cell under saline conditions. Furthermore, salt entry into the chloroplast stroma may be critical for grana formation and photosystem II activity in halophytes but not in glycophytes. Salt also inhibits some stromal enzymes (e.g. fructose-1,6-bisphosphatase) to a lesser extent in halophyte species. Halophytes accumulate more chloride in chloroplasts than glycophytes and appear to use sodium in functional roles. We propose the molecular identities of candidate transporters that move sodium, chloride and potassium across chloroplast membranes and discuss how their operation may regulate photochemistry and photosystem I and II activity in chloroplasts.
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© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved.