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Key Message: The RING-type E3 ligase AtPPRT3 participates in the plant ABA responding as a positive regulator. E3 ubiquitin ligase, alike of classic plant stress resistance proteins, plays a vital role in regulating the degradation of stress-related proteins. In this study, we investigated the function of the RING-type E3 ubiquitin ligase AtPPRT3 in the ABA signaling pathway. AtPPRT3, located in the endoplasmic reticulum membrane, is involved in ABA signaling. The transcriptional expression of AtPPRT3 was induced by ABA, and the promoter region upstream of AtPPRT3 contains the ABA-responsive element (ABRE). Additionally, the β-glucuronidase (GUS) gene driven by the AtPPRT3 promoter was up-regulated in transgenic plants after ABA treated. We obtained AtPPRT3 function-deficient mutants atpprt3-1, atpprt3-2, and AtPPRT3 over-expressing lines (OE4 and OE5). In this study, atpprt3-1 and atpprt3-2 were less sensitive to exogenous ABA compared to Col-0, whereas OE4 and OE5 were more sensitive. Moreover, AtPPRT3 promotes ABA-mediated stomatal closure and inhibits water loss in Arabidopsis thaliana. After exogenous ABA treated, the transcriptional expression levels of AtDREB2A, AtKIN1, AtRD29A, AtERD10 and AtRD29B were up-regulated to greater extents in OEs and lower extents in atpprt3-1 and atpprt3-2 compared to Col-0. These results suggest that AtPPRT3 positively regulates ABA signaling in A. thaliana.

Key message: The RING-type E3 ligase AtARRE participates in the plant ABA responding as a negative regulator.Abstract: Ubiquitination protease system (UPS) is significant in post-transcriptional regulation. In UPS, E3 ligase recognizes the substrate protein and mediates the polyubiquitin chain onto the substrate. Here, we identified a new gene, named Arabidopsis thaliana ABA-related RING-type E3 ligase (AtARRE), which induced by ABA and NaCl. AtARRE encodes a functional RING-type E3 ligase protein localized in nucleus and plasma membrane of Arabidopsis. Physiological analysis demonstrated that mutation of AtARRE (T-DNA insert mutants atarre-1 and atarre-2) caused plants hypersensitivity to ABA, including enhanced stomatal closure, reduced root elongation and seed germination. However, overexpression of AtARRE transgenic lines caused plants hyposensitive to ABA compared with WT and mutant atarre plants. Under the treatment of ABA, the transcript abundances of ABA-responsive genes RD29A, RD29B, RD22 and ABI5 in atarre mutant plants were markedly higher than those of WT and AtARRE overexpression lines. Hence, these results indicate that AtARRE acts as a negative regulator of ABA-mediated stress responses in Arabidopsis. [ABSTRACT FROM AUTHOR]