Engineering ion flux of the stomatal complex for enhanced photosynthesis and water use efficiency

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We propose a concerted assessment of stomatal kinetics and its relevance to crop yields and water use. Our aims are (1) to demonstrate the feasibility of manipulating stomatal kinetics by translating knowledge of BLINK1 optogenetics in Arabidopsis into two crop models, and (2) to test the hypothesis of a two-cell, two-stroke 'pump' for solute transfer as a target for further enhancements in accelerating stomatal kinetics. In the latter case, we propose (i) a quantitative analysis of the ion transport characteristics of the surrounding cells and their coordination with stimuli known to trigger guard cell transport for stomatal opening and closing, and (ii) optogenetic and related manipulations of K+ flux of the surrounding cells in order to understand the transport coordination between surrounding and guard cells.

We will build on our recent success with the light-activated K+ channel BLINK1 in Arabidopsis in each case. Both the practical and fundamental challenges will take advantage of targeted optogenetic expression within the leaf epidermis and, additionally, on the development of new optogenetic tools with improved light sensitivities and altered light regulation. Experiments will follow methodologies similar to those used successfully to date, including voltage clamp, gas exchange and biomass studies. We will use extant knowledge of BLINK1 variants in extending the optogenetic tools, and we will draw on heterologous expression to identify and quantify the most promising of these prior to use. Finally, we will target expression between cell types to assess, in response to light, the component contributions from the surrounding and guard cells and to extract stomatal kinetics and their coupling to photosynthesis. We expect these studies to expand our fundamental understanding of stomatal mechanics and to establish their kinetics as a bona fide target for future efforts in crop improvement.

This proposal is for a synergy in practical and fundamental research building on a core of ideas at the centre of the international plant photosynthesis and stomatal biology communities. The research will stimulate thinking around strategies for enhancing crop yields and reducing agricultural water consumption, and it should inform methodologies for approaching crop engineering. In the long term the research is expected to benefit fundamental researchers as well as agriculture and industry through conceptual developments as well as the introduction of new technologies relevant to plant productivity and water use efficiency. The research will feed into higher education training programmes through capacity building at the postgraduate and postdoctoral levels. Additional impact is proposed through public displays and the development of teaching resources building on the background work for this proposal. Finally the research will help guide future efforts in applications to agricultural/industrial systems. The applicants have established links with industrial/technology transfer partners and research institutes to take advantage of these developments. Further details of these, and additional impacts will be found in Part 1 of the Case for Support and in the attached Impact Pathways.