Over‐Expression of AtATG8h Enhances Resistance Against Biotrophic Pathogens but Compromises Resistance Against Necrotrophic Pathogen in Arabidopsis

AtATG8h and AtATG8i belong to a unique sub-group of the nine ATG8 proteins encoded in the Arabidopsis genome. Unlike other ATG8s that need ATG4 protease for cleavage to expose their C-terminal Gly residue for attachment of phosphatidylethanolamine (PE) and thus subsequent recruitment to the autophagosomal membranes, AtATG8h and AtATG8i directly carry a Gly residue at their C-termini and can be lipidated without the action of ATG4. We previously showed that CLATHRIN LIGHT CHAIN 2 (CLC2) participates in the autophagy process via interacting with AtATG8h and AtATG8i. Simultaneously knocking out AtATG8h and AtATG8i by CRISPR/CAS9 technology compromised autophagy, and as a consequence, enhanced the resistance to a biotrophic fungal pathogen. In this study, we took a gain-of-function approach to further investigate the roles of AtATG8h in disease resistance. Our results showed that overexpression of AtATG8h enhanced the resistance to biotrophic bacterial and fungal pathogens but compromised the resistance to a toxin secreted from a necrotrophic fungal pathogen. The enhanced resistance to the biotrophic pathogens was correlated with the increased expression of Pathogenesis-related (PR) gene, enhanced callose deposition and levels of both salicylic acid (SA) and H₂O₂, whereas the compromised resistance to the necrotrophic fungal toxin was correlated with the significantly reduced expression of the genes in the jasmonic acid (JA) pathway. These results indicated that either knocking out or overexpressing AtATG8h resulted in a similar outcome in Arabidopsis disease resistance. The underpinning molecular mechanism is discussed.