ABI3 mediated repression of RAV1 gene expression promotes efficient dehydration stress response in Arabidopsis...

Dehydration stress response is a complex mechanism in plants involving several factors and hormone signalling pathways. RAV1 is a member of the AP2/ERF family of transcription factors that works in various developmental pathways. Here we show that downregulation of RAV1 gene expression is important for efficient dehydration stress response. Interestingly, the B3-domain transcription factor ABI3 negatively regulates RAV1 expression. In absence of ABI3, RAV1 expression increases during dehydration stress compared to control. As a part of stress response, ABI3 occupancy increases in the RAV1 promoter region. Such regulation of RAV1 gene expression seems vital as absence of RAV1 leads to reduced water loss during dehydration stress and consequently faster recovery compared to wild type. rav1 mutant seedlings show more abundant root growth under control condition and higher primary root elongation compared to wild type when subjected to dehydration stress. Mutants also exhibit enhanced ABA sensitivity compared to wild type. At the transcript level, rooting genes like NAC1, ARF16, SLR and SLR-downstream genes like ARF7, PLT3, SHR show differential expression in rav1 mutant, compared to wild type. Additionally, ethylene-responsive genes ETR1, EIN2 and ERF1 also get differentially expressed in presence and absence of RAV1 under control and stress conditions. This indicates an altered ethylene response in the rav1 mutant. All these features render rav1seedlings better equipped for responding to dehydration stress. It thus becomes evident that ABI3 mediated regulation of RAV1 gene expression is a significant part of dehydration stress signalling for efficient stress management at the molecular and morphological level.