SCF OsFBK1 E3 ligase mediates jasmonic acid induced turn-over of OsATL53 and OsCCR14 to regulate rice anther and root lignification.

We have shown earlier the F-box protein, OsFBK1, mediating turn-over of a cinnamoyl CoA-reductase, OsCCR14, to regulate rice anther and root lignification. Currently, we have identified OsATL53, a member of ATL family of RING-H2 proteins interacting with OsCCR14 in cytoplasm. OsATL53 was identified in the same Y2H library screening as reported before for OsCCR14. OsATL53 has been found to have a cytoplasmic localization and has E3 ligase ubiquitination properties. SCF OsFBK1 mediates turn-over of OsATL53 in cytoplasm and nucleus, while of OsCCR14 in the nucleus as validated by cell-free degradation assays. In presence of jasmonic acid (JA), which plays a role in anther dehiscence, confocal FLIM analyses demonstrate OsATL53-OsCCR14 undergoing conformational changes that trigger the complex to accumulate around the nuclear periphery and signals OsFBK1 to initiate degradation of the proteins in respective cellular compartments. Biochemically, OsATL53 decreases enzymatic activity of OsCCR14 and sequesters it in the cytoplasm thereby regulating the lignification process. Knock-down rice transgenics of OsATL53 display increased lignin deposition in the anthers and roots vis-a-vis wild-type, while those of OsCCR14 have decreased lignin content. These data show OsATL53 affects activity of OsCCR14, and their JA induced degradation by SCF OsFBK1 regulates lignification of rice anthers and roots.