The SCF E3 Ligase AtPP2-B11 Plays a Negative Role in Response to Drought Stress in Arabidopsis

Ubiquitination is a eukaryotic post-translational protein modification, implicated in various cellular processes in higher plants, and E3 ligases play an essential role in this cascade. In this study, we identified an Skp1-Cullin-F-box (SCF) E3 ligase encoding gene, Arabidopsis phloem protein 2-B11 (AtPP2-B11; At1g80110), by searching drought-responsive element in the promoter regions of 1,488 putative E3s in the Arabidopsis genome. The expression of AtPP2-B11 in seedlings was remarkably induced with increased duration of drought treatment. Transgenic lines overexpressing AtPP2-B11 exhibited obvious hypersensitivity to drought stress during seed germination and in mature plants. Protein interaction assay with Arabidopsis Skp1 (ASK) proteins showed that AtPP2-B11 strongly interacted with ASK 7, ASK 18, and ASK 19, respectively, indicating that AtPP2-B11 may function as an F-box protein. An AtPP2-B11-interacting protein, AtLEA14, was identified by a yeast two-hybrid screening and bimolecular fluorescence complementation assay. Real-time quantitative RT-PCR and Western blot analysis showed that the transcript and protein levels of AtLEA14 decreased in 35S::AtPP2-B11 transgenic plants subjected to drought conditions. Transgenic Arabidopsis plants overexpressing AtPP2-B11 showed altered expression of abiotic stress response marker genes (COR15a, COR47, ERD10, KIN1, RAB18, and RD22) under both normal and drought conditions. Overall, these results suggested that AtPP2-B11, a SCF E3 ligase, played an important role in response to drought stress as a negative regulator in Arabidopsis.