Arabidopsis RAV1 transcription factor, phosphorylated by SnRK2 kinases, regulates the expression of ABI3,ABI4, and ABI5 during seed germination and early seedling development

Abstract

These three authors contributed equally to this work. SUMMARYThe phytohormone abscisic acid (ABA) modulates a number of processes during plant growth and development. In this study, the molecular mechanism of Arabidopsis RAV (Related to ABI3/VP1) transcription factor RAV1 involving ABA signaling was investigated. RAV1-underexpressing lines were more sensitive to ABA than wild-type plants during seed germination and early seedling development, whereas RAV1-overexpressing lines showed strong ABA-insensitive phenotypes. Overexpression of RAV1 repressed ABI3, ABI4, and ABI5 expression, and RAV1 bound to the ABI3, ABI4, and ABI5 promoters in vitro and in vivo, indicating that RAV1 directly down-regulates the expression of ABI3, ABI4, and ABI5. The interruption of ABI5 function in RAV1-U abi5 plants abolished the ABA-hypersensitive phenotype of RAV1-U plants, demonstrating that ABI5 is epistatic to RAV1. RAV1 interacted with SNF1-RELATED PROTEIN KINASE SnRK2.2, SnRK2.3 and SnRK2.6 in the nucleus. In vitro kinase assays showed that SnRK2.2, SnRK2.3 and SnRK2.6 phosphorylated RAV1. Transient expression assays revealed that SnRK2.2, SnRK2.3 and SnRK2.6 reduced the RAV1-dependent repression of ABI5, and the ABA-insensitive phenotype of the RAV1-overexpressing line was impaired by overexpression of SnRK2.3 in the RAV1 OE3 plants. Together, these results demonstrated that the Arabidopsis RAV1 transcription factor plays an important role in ABA signaling by modulating the expression of ABI3, ABI4, and ABI5, and that its activity is negatively affected by SnRK2s.

A Predictive Coexpression Network Identifies Novel Genes Controlling the Seed-to-Seedling Phase Transition in Arabidopsis thaliana

“…Expression profiles for each gene of single stages of the transition matched with known expression profiles (Ding et al, 2006;Tepperman et al, 2006;Hammani et al, 2011;Narsai et al, 2011;Feng et al, 2014), validating the data set. Expression data across the seven developmental stages displayed high reproducibility.…”

“…Expression data are hosted in the National Center for Biotechnology Information Gene Expression Omnibus database (http://www.ncbi.nlm.nih.gov/ geo/query/acc.cgi?token=onyxsyycjtaxxux&acc=GSE65394). Validation of the seed-to-seedling transcriptome data set was performed by comparison with previously published expression patterns of genes known to be differentially expressed across seed-to-seedling developmental stages (Supplemental Table S1; Ding et al, 2006;Tepperman et al, 2006;Hammani et al, 2011;Narsai et al, 2011;Feng et al, 2014).…”

Phosphorylation of ARF2 Relieves Its Repression of Transcription of the K+ Transporter Gene HAK5 in Response to Low Potassium Stress

“…In the ABA signaling pathway, transcription factor RAV1 represses the expression of ABI3, ABI4, and ABI5. Protein kinases SnRK2s are activated by the ABA signal and then phosphorylate RAV1, which removes RAV1 repression on ABI5 transcription (Feng et al, 2014). Here, we demonstrated that low-K + stress triggers a rapid phosphorylation of ARF2 ( Figure 9B).…”

ABA receptor PYL9 promotes drought resistance and leaf senescence

“…4 D and E). ABA-activated SnRK2s phosphorylate RAV1 (30), which positively regulates leaf senescence in Arabidopsis (31). According to the Arabidopsis eFP browser, expression of ORE1, ORS1, and AtNAP is enhanced by ABA (Fig.…”