Generating cell-type-specific multi-targeted amiRNA and CRISPR libraries to reveal ABA delivery mechanisms

Climate changes and population growth present significant challenges to global food security. Plants are subjected to environmental stresses which affect plant growth and productivity and result in yield loss worldwide. Plants utilize the phytohormone abscisic acid (ABA) to cope with these challenges, as it regulates various processes including drought tolerance, growth and development. Up to date, the molecular mechanisms that determine ABA movement towards the guard cells to promote stomatal closure and resist abiotic stresses are not entirely clear. To understand where ABA synthesis occurs in the leaf and to identify redundant ABA-specific transporters, we have developed a new system that exploits two properties: First, the ability to control ABA synthesis at a high spatiotemporal resolution. Second, the ability to silence gene families in a “transportome-scale” cell-type-specific level. To control ABA production, we have generated aba2-1, pSUC2:XVE:ABA2 plants. Inducible phloem-specific ABA biosynthesis fully complemented the leaf ABA developmental and physiological deficiency. We have established a unique targeted transportome-scale, forward-genetic approach to overcome functional redundancy in this background. We generated a new amiRNA library containing 5,655 amiRNAs designed to target multiple transporters, driven under cell-type specific promoters. We revealed putative ABA transporters that are involved in ABA movement from the phloem to the guard cells. This work is expected to reveal how plants balance ABA localization and homeostasis to define leaf physiology and adaptation to abiotic stresses.