Arabidopsis Positively Regulates ABA Signaling by Changing the Expression Pattern of ABA-Responsive Proteins.

Phytohormone ABA regulates the expression of numerous genes to significantly affect seed dormancy, seed germination and early seedling responses to biotic and abiotic stresses. However, the function of many ABA-responsive genes remains largely unknown. In order to improve the ABA-related signaling network, we conducted a large-scale ABA phenotype screening. LSH, an important transcription factor family, extensively participates in seedling development and floral organogenesis in plants, but whether its family genes are involved in the ABA signaling pathway has not been reported. Here we describe a new function of the transcription factor in an ABA signaling pathway. In this study, we found that was localized in the nucleus, and the expression level of was significantly induced by exogenous ABA at the transcription level and protein level. Meanwhile, seed germination and root length measurements revealed that mutant lines were ABA insensitive, whereas overexpression lines showed an ABA-hypersensitive phenotype. With further TMT labeling quantitative proteomic analysis, we found that under ABA treatment, ABA-responsive proteins (ARPs) in the mutant presented different changing patterns with those in wild-type Col4. Additionally, the number of ARPs contained in the mutant was 397, six times the number in wild-type Col4. In addition, qPCR analysis found that under ABA treatment, positively mediated the expression of downstream ABA-related genes of , , and . These results indicate that in Arabidopsis, is a novel ABA regulator that could specifically change the expression pattern of APRs to positively mediate ABA responses.