Abscisic acid (ABA) is a plant hormone with regulatory roles spanning growth, development, and responses to abiotic and biotic stress. ABA is a key regulator of seed dormancy and ABA signaling is essential for dormancy. A number of studies have used genetic, omic and chemical approaches to dissect dormancy, with significant success. These approaches have led to better understanding of the genetic pathways involved including elucidation of the core ABA signaling pathway and the physiological responses, including ABA’s significant role in thermoinhibition. However, redundancy in the core ABA signaling pathway complicates genetic approaches, and chemical approaches are limited to compounds with herbicidal effects or lack of potency. To address these limitations, we developed antabactin (ANT), a potent ABA receptor antagonist, as a versatile research tool and agrochemical. The backbone of a potent ABA receptor agonist, Opabactin, was functionalized with a chemical library through click chemistry to generate a library of chemicals which were tested for antagonist activity and then optimized to produce ANT. ANT acts as a pan-receptor antagonist, effectively disrupting receptor-PP2C interactions. Our findings highlight ANT's efficacy in both in vitro and in planta. ANT application significantly speeds seed germination in barley, tomato, and Arabidopsis, and additionally it restores germination in thermoinhibited Arabidopsis, confirming ABA's role in thermoinhibition regulation. We also showed that, through ANT application, blocking ABA signaling fully restores germination in thermoinhibited lettuce and can be used in priming treatments to improve germination.
Beyond confirming ABA's role in thermoinhibition, we establish DELAY OF GERMINATION 1 (DOG1) as the primary regulator of dormancy and after-ripening. DOG1, a protein with unknown molecular function, is another key regulator of seed dormancy. By employing innovative seed germination phenotyping and image analysis techniques, we delineated the relative significance of these two key dormancy regulators in optimal conditions establishing DOG1 as the primary dormancy regulator over ABA in unstressed conditions. Lastly, we identified a germination-related locus in Arabidopsis through an association study, utilizing ANT to block ABA signaling.
This comprehensive exploration underscores Antabactin's potential as an agrochemical and as a tool for advancing our understanding of ABA’s role in dormancy regulation in plants. ANT's versatility offers promising avenues for future research and an increased understanding of plant growth and development.