Photosystem II Subunit S overexpression increases the efficiency of water use in a field-grown crop

Katarzyna Głowacka,Katherine Kucera,Amanda P Cavanagh,Johannes Kromdijk,Krishna K Niyogi,Lauriebeth Leonelli,Andrew D B Leakey,Jiayang Xie,Stephen P Long,Donald R Ort

doi:10.1038/s41467-018-03231-x

Abstract

Insufficient water availability for crop production is a mounting barrier to achieving the 70% increase in food production that will be needed by 2050. One solution is to develop crops that require less water per unit mass of production. Water vapor transpires from leaves through stomata, which also facilitate the influx of CO2 during photosynthetic assimilation. Here, we hypothesize that Photosystem II Subunit S (PsbS) expression affects a chloroplast-derived signal for stomatal opening in response to light, which can be used to improve water-use efficiency. Transgenic tobacco plants with a range of PsbS expression, from undetectable to 3.7 times wild-type are generated. Plants with increased PsbS expression show less stomatal opening in response to light, resulting in a 25% reduction in water loss per CO2 assimilated under field conditions. Since the role of PsbS is universal across higher plants, this manipulation should be effective across all crops.

Highlights

Insufficient water availability for crop production is a mounting barrier to achieving the 70% increase in food production that will be needed by 2050
Transpiration is proportional to the water vapor pressure deficit (VPD) from leaf to air, which represents the gradient between the humidity in leaf internal airspaces and drier air surrounding the leaf
PSBS-28, PSBS43, psbs-4, and WT N. tabacum plants were grown in a controlled-environment cabinet and Photosystem II Subunit S (PsbS) transcript and protein levels were measured in samples from the youngest fully expanded leaves

Summary

Introduction

Insufficient water availability for crop production is a mounting barrier to achieving the 70% increase in food production that will be needed by 2050. In tobacco plants containing reduced amounts of cytochrome b6/f13, ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco)[13,14], glyceraldehyde 3-phosphate dehydrogenase[15], or sedoheptulosebisphosphatase[16] net assimilation rate was substantially reduced, but stomatal conductance often remained relatively unaltered compared to the wild-type (WT) These results show clearly that the stomatal opening signal does not scale directly with the rate of CO2 uptake. QA is the primary electron acceptor downstream of photosystem II and its oxidation state reflects the balance between excitation energy at photosystem II and the rate of the Calvin–Benson cycle This predicts that decreasing the excitation pressure at photosystem II should directly affect stomatal opening in response to light by keeping

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Results

Conclusion