456 / 2019-02-26 14:23:12

Unravelling a potential pathway linking plasma membrane to chloroplasts and its role in the regulation of plant defence responses

TYLCV,Chloroplast,Defence,N-myristoylation,Tomato,Target signal,Geminivirus

全体主题 > Biotic Stress

Plant pathogens need to suppress plant defence responses in order to establish a successful infection. Plants have diverse strategies against viral invasion, which include production of defensive hormones such as salicylic acid (SA). C4, a small protein encoded by Tomato yellow leaf curl virus and essential for infectivity, contains two overlapping localization signals, an N-myristoylation motif and a chloroplast transit peptide, and consistently localizes in two distinct subcellular compartments, namely plasma membrane (PM) and chloroplasts (1). PM localization overrides chloroplast localization, since a non-myristoylable mutant version of C4 (C4G2A) localizes to chloroplasts exclusively; moreover, activation of defence responses leads to a re-localization of C4 from PM to chloroplasts. We have found that C4G2A interferes with retrograde signaling from the chloroplast through the interaction with the chloroplast calcium sensing receptor protein, CAS, which is required for the pathogen-associated molecular patterns (PAMP)-induced expression of defence genes, SA biosynthesis, and regulation of cytoplasmic calcium oscillations (2), all of them repressed by C4G2A. Interestingly, this dual localization is also present in a number of pathogen effectors and in a subset of defence-related plant proteins. These findings suggest that an intrinsic route in plants delivering proteins from the PM to chloroplasts might be hijacked by plant pathogens to suppress defence responses.