The Mechanism Of Short-term And Continuing ABA Interplay With Multiple Hormones To Regulate Plant Survival And Growth

The stress phytohormone, abscisic acid (ABA), plays important roles in facilitating plants to survive and grow well under a wide range of stress conditions. Previous gene expression studies mainly focused on plant responses to short-term ABA treatment, but the effect of sustained ABA treatment is poorly studied. Particularly, the difference between initial and continuing stress treatments is largely unknown. Here, we treated plants with ABA for one hour or nine days, and our genome-wide analysis indicated that the differentially-regulated genes under the two conditions were tremendously different. We analyzed other hormones’ signalling changes by using their whole sets of known responsive genes as reporters and integrating feedback regulation of their biosynthesis. We found that under short-term ABA treatment, signaling outputs of growth-promoting hormones, brassinosteroids and gibberellins, and a biotic stress-responsive hormone, jasmonic acid, were significantly inhibited, while auxin and ethylene signaling outputs were promoted, which may be required to maintain basal growth and develop alternative stress response pathways, respectively. However, sustained ABA treatment repressed cytokinin and gibberellin signaling, but stimulated auxin signaling. Using several sets of hormone-related mutants, we found several candidates in corresponding hormonal signaling pathways, including some receptors or transcription regulators, are essential in responding to ABA. Our findings indicate that interactions of ABA-dependent stress signals with specific hormones at different levels are required for plants to survive under transient stress and to adapt to continuing stressful environments.