Abscisic Acid Analogues That Act as Universal or Selective Antagonists of Phytohormone Receptors

The plant hormone abscisic acid (ABA) plays many important roles in controlling plant development and physiology, from flowering to, senescence. ABA is now known to exert its effects through a-family of soluble ABA receptors which in Arabidopsis-thaliana has 13 members divided into three clades. Homologues of these receptors are present in other plants, also relatively large numbers. Investigation of the roles of each homologue in mediating the diverse physiological roles of ABA is hampered by this genetic redundancy. We report herein the in vitro screening, of a targeted ABA-like analogue libraty and identification of novel antagonist hits, including the analogue PBI686 that had been developed previously as a-probe for identifying ABA-binding proteins. Further in vitro characterization of PBI686 and development of second-generation leads yielded both receptor-selective and universal antagonist hits. In planta assays in different species have demonstrated that these antagonist leads can overcome various ABA-induced physiological change's. While the general antagonists open lip hitherto unexplored avenue for controlling plant growth through inhibition of ABA-regulated physiological processes, the receptor selective, antagonist,can be developed into chemical probes to explore the physiological roles Of individual receptors.