Arabidopsis PAD4 lipase-like domain is a minimal functional unit in resistance to green peach aphid

Abstract

Plants have evolved mechanisms to attract beneficial microbes and insects while protecting themselves against pathogenic microbes and pests. In Arabidopsis, the immune regulator PAD4 functions with its cognate partner EDS1 to limit pathogen growth. PAD4, independently of EDS1, reduces infestation by Green Peach Aphid (GPA). How PAD4 regulates these defense outputs is unclear. By expressing the N-terminal PAD4-lipase-like domain (LLD) without its C-terminal ‘EDS1-PAD4’ (EP) domain, we interrogated PAD4 functions in plant defense. Here we show that transgenic expression of PAD4^LLD in Arabidopsis is sufficient for limiting GPA infestation, but not for conferring basal and effector-triggered pathogen immunity. This suggests that the C-terminal PAD4-EP domain is necessary for EDS1-dependent immune functions. Moreover, PAD4^LLD is not sufficient to interact with EDS1, indicating the PAD4-EP domain is required for heterodimerisation. These data provide molecular evidence that PAD4 has domain specific functions.