GPA5 encodes a Rab5a effector required for post-Golgi trafficking of rice storage proteins ($) (Plant Cell)

Storage proteins secreted into vacuoles during seed development serve as precursors for germination and plant growth. In this paper, Ren et al. identified a regulator, GLUTELIN PRECURSOR ACCUMULATION 5 (GPA5) that is involved in protein trafficking into the vacuoles during seed development. The loss of function mutant gpa5 was identified through a mutant screen for defects in the vacuolar storage protein transport pathway resulting in the accumulation of glutelin precursor in the apoplast. GPA5 encodes for a phox homology domain-containing protein and is primarily expressed in the prevacuolar compartment/dense vesicles that is necessary for protein trafficking from Golgi to storage vacuoles during seed development. Further, the authors have identified that GPA5 interacts with other regulators of the protein sorting pathway, Rab5a and VPS9a and expression of GPA5 is altered in rab5a and vps9a mutants. Also, GPA5 interacts with a class C core vacuole/endosome tethering (CORVET) complex and VAMP727-containing R-soluble NSF attachment protein receptor (SNARE) complex. Thus, the authors identified a key regulator, GPA5 involved in sorting of storage proteins into vacuoles of developing seeds. (Summary by Suresh Damodaran) Plant Cell 10.1105/tpc.19.00863