Arabidopsis Functions in the ABA Signaling Pathway and Is Regulated by Proteolysis.

Plants have evolutionarily established resistance responses to a variety of abiotic stress conditions, in which ABA mediates the integrated regulation of these stress responses. Numerous proteins function at the transcription level or at the protein level when contributing to controls of the ABA signaling process. Although osmotin is identified as a salt-inducible protein, its function in the abiotic stress response is yet to be elucidated. To examine the role of Arabidopsis () in the ABA signaling pathway, a deletion mutant generated by a CRISPR/Cas9 system and the double mutant () were analyzed for various ABA responses. Both and showed reduced levels of ABA responses in seeds and leaves. Moreover, proline level and expression of the proline biosynthesis gene was significantly reduced in Interestingly, OSM34 binds to SKP2A, an F-Box protein whose transcription is induced by ABA. The protein stability of OSM34 was determined to be under the control of the 26S proteasome. In conclusion, our data suggest that OSM34 functions as a positive regulator in the generation of ABA responses and is under post-translational control.