Ubiquitination is a critical post-translational protein modification that has been implicated in diverse cellular processes, including abiotic stress responses, in plants. In the present study, we identified and characterized a T-DNA insertion mutant in the At5g10650 locus. Compared to wild-type Arabidopsis plants, at5g10650 progeny were hyposensitive to ABA at the germination stage. At5g10650 possessed a single C-terminal C3HC4-type Really Interesting New Gene (RING) motif, which was essential for ABA-mediated germination and E3 ligase activity in vitro. At5g10650 was closely associated with microtubules and microtubule-associated proteins in Arabidopsis and tobacco leaf cells. Localization of At5g10650 to the nucleus was frequently observed. Unexpectedly, At5g10650 was identified as JAV1-ASSOCIATED UBIQUITIN LIGASE1 (JUL1), which was recently reported to participate in the jasmonate signaling pathway. The jul1 knockout plants exhibited impaired ABA-promoted stomatal closure. In addition, stomatal closure could not be induced by hydrogen peroxide and calcium in jul1 plants. jul1 guard cells accumulated wild-type levels of H2O2 after ABA treatment. These findings indicated that JUL1 acts downstream of H2O2 and calcium in the ABA-mediated stomatal closure pathway. Typical radial arrays of microtubules were maintained in jul1 guard cells after exposure to ABA, H2O2, and calcium, which in turn resulted in ABA-hyposensitive stomatal movements. Finally, jul1 plants were markedly more susceptible to drought stress than wild-type plants. Overall, our results suggest that the Arabidopsis RING E3 ligase JUL1 plays a critical role in ABA-mediated microtubule disorganization, stomatal closure, and tolerance to drought stress.
Bibliographical noteFunding Information:
This work was supported by grants from the National Research Foundation (Mid-Career Researcher Program, Project no. 2017R1A2B2006750/2020R1A2B5B02001590 and Basic Science Research Program, Project Number 2018R1A6A1A03025607, Republic of Korea) to W.T.K. S.G.Y was a recipient of Hyundai Motor Chung Mong-Koo Foundation Scholarship.
All Science Journal Classification (ASJC) codes
- Plant Science
- Cell Biology