| Project Detail |
Plants have evolved a sophisticated system to perceive and transmit external stimuli to the cell interior and inform growth and defense. The host lab discovered a new pathway linking the PM to chloroplasts and regulating defence, based on inducible protein re-localization, co-opted by pathogens during evolution. Both the plant protein CALCIUM DEPENDENT PROTEIN KINASE 16 (CPK16) and the viral protein C4 from tomato yellow leaf curl virus re-localize from the PM to chloroplasts upon activation of pathogen associated molecular pattern (PAMP)-triggered immunity (PTI); from the organelle, CPK16 acts as a positive regulator of downstream defence responses, while C4 acts as a suppressor. However, the molecular and cellular events enabling and regulating protein trafficking from PM to chloroplasts remain elusive. Preliminary data in the host lab found the colocalization of C4 with SYP61- and Ara7-positive compartments upon flg22 treatment; among them, C4 colocalizes with Ara7 at the periphery of chloroplasts. Upon flg22 treatment, CPK16 was also able to form mobile dots in the cytoplasm. These results suggest that endocytosis is likely to be involved in C4/CPK16 trafficking from the PM to chloroplasts. In addition, phosphorylation regulation and N-terminal cleavage could also regulate the PM-to-chloroplast protein trafficking as evidenced by mass spectrometry analyses. In this project, I will utilize both CPK16 and C4 to investigate the molecular determinants underlying the protein trafficking from the cell surface to chloroplasts, including how proteins are transported from the PM to chloroplasts (Objective 1) and how N-myristoylated C4 and CPK16 are released from membrane compartments prior to chloroplast import (Objectives 2). By using cell biology, protein biochemistry, molecular biology, and plant genetic methods, this project will expand our understanding of the PM-to-chloroplast protein trafficking and serve as stepping stone for the engineering of immune responses. |
