The Asparagine-Rich Protein NRP Facilitates the Degradation of the PP6-type Phosphatase FyPP3 to Promote ABA Response in Arabidopsis

The phytohormone abscisic acid （ABA） plays critical roles in abiotic stress responses and plant develop- ment. In germinating seeds, the phytochrome-associated protein phosphatase, FyPP3, negatively regulates ABA signaling by dephosphorylating the transcription factor ABI5. However, whether and how FyPP3 is regulated at the posttranscriptional level remains unclear. Here, we report that an asparagine-rich protein, NRP, interacts with FyPP3 and tethers FyPP3 to SYP41/61-positive endosomes for subsequent degradation in the vacuole. Upon ABA treatment, the expression of NRP was induced and NRP-mediated FyPP3 turnover was accelerated. Consistently, ABA-induced FyPP3 turnover was abolished in an nrp null mutant. On the other hand, FyPP3 can dephosphorylate NRP in vitro, and overexpression of FyPP3 reduced the half-life of NRP in vivo. Genetic analyses showed that NRP has a positive role in ABA-mediated seed germination and gene expression, and that NRP is epistatic to FyPP3. Taken together, our results identify a new regulatory circuit in the ABA signaling network, which links the intracellular trafficking with ABA signaling.

ESCRT-Ⅲ component OsSNF7.2 modulates leaf rolling by trafficking and endosomal degradation of auxin biosynthetic enzyme OsYUC8 in rice

The endosomal sorting complex required for transport(ESCRT)is highly conserved in eukaryotic cells and plays an essential role in the biogenesis of multivesicular bodies and cargo degradation to the plant vacuole or lysosomes.Although ESCRT components affect a variety of plant growth and development processes,their impact on leaf development is rarely reported.Here,we found that OsSNF7.2,an ESCRT-Ⅲ component,controls leaf rolling in rice(Oryza sativa).The Ossnf7.2 mutant rolled leaf 17(rl17)has adaxially rolled leaves due to the decreased number and size of the bulliform cells.OsSNF7.2is expressed ubiquitously in all tissues,and its protein is localized in the endosomal compartments.OsSNF7.2 homologs,including OsSNF7,OsSNF7.3,and OsSNF7.4,can physically interact with OsSNF7.2,but their single mutation did not result in leaf rolling.Other ESCRT complex subunits,namely OsVPS20,OsVPS24,and OsBRO1,also interact with OsSNF7.2.Further assays revealed that OsSNF7.2 interacts with OsYUC8 and aids its vacuolar degradation.Both Osyuc8and rl17 Osyuc8 showed rolled leaves,indicating that OsYUC8 and OsSNF7.2 function in the same pathway,conferring leaf development.This study reveals a new biological function for the ESCRT-Ⅲcomponents,and provides new insights into the molecular mechanisms underlying leaf rolling.