Clathrin Light Chains are essential in negative regulation of cell death and immunity in Arabidopsis through interacting with autophagy pathway

Abstract

Clathrin plays a critical role in clathrin-mediated endocytosis (CME) in plants, and it is required for autophagy in mammals. However, the functional interconnection of clathrin with autophagy has not been firmly established in plants. We demonstrate that loss of function of clathrin light chain (CLC) subunit 2 and 3 results in salicylic acid (SA)- and H2O2-dependent accelerated senescence and activated defense responses in Arabidopsis, which are hallmarks displayed in autophagy-related gene (ATG) mutants. Similar to atg mutants, the clc2-1clc3-1 double mutant has enhanced sensitivity to both carbon and nitrogen starvation and enhanced resistance to biotrophic bacterial and fungal pathogens. In addition, the autophagy flux was significantly reduced in the roots of clc2-1clc3-1 mutant plants relative to Col-0 plants under carbon starvation conditions. Furthermore, our Yeast-2-hybrid (Y2H) and Luciferase complementation assays showed that CLC2 directly interacted with ATG8h and ATG8i. Mutations within the unique ATG8-interacting motif (AIM) of CLC2 as well as at the LIR/AIM-docking site of ATG8h abolished the interaction between CLC2 and ATG8h. As anticipated, both GFP-ATG8h/GFP-ATG8i and CLC2 were subjected to autophagic degradation in the vacuoles. Together, our data revealed that the accelerated senescence and activated immune responses observed in Arabidopsis clc2-1clc3-1 mutant plants result from impaired autophagy, and CLC2 participates in autophagy through directly interactions with ATG8h and ATG8i in an AIM- and LDS-dependent manner. Our results unveil a previously unidentified link between the function of CLCs and autophagy.