Optogenetic Manipulation of Guard Cell Ion Transport Enhances Plant Water Use Efficiency and Carbon Capture

Plant growth and productivity are strongly correlated with water availability that has been a limiting factor, especially at arable lands. The demand for engineering crops to withstand such extreme conditions without jeopardising growth and yield is higher than ever. The control of ion transport in guard cells dictates stomatal movements enabling the uptake of CO₂ in expense of water vapour release, and therefore optimizing the trade-off between transpirational water loss and carbon gain. Here, we showcase the potential of optogenetic engineering to modulate guard cell ion transport in order to improve water use efficiency. Blue light activation of blue-light gated K⁺ channel (BLINK) was confirmed in mutants impaired in stomatal opening under blue light. We further validated the photoactivation of BLINK by showing the BLINK-expressing lines having higher K⁺ conductance in blue light. Gas exchange measurements revealed faster stomatal movements and improved water use of BLINK-expressing plants when grown under fluctuating light condition, and in combination with water stress. We therefore propose the use of BLINK as an optogenetic tool to alter stomatal behaviour and improve water use efficiency without a penalty in carbon fixation.