A Putative Lipase-like Protein Regulates Arabidopsis Immune Gene Expression and Defense Responses
C. LIU (1), F. Cui (1), P. He (2), L. Shan (1) (1) Department of Plant Pathology and Microbiology, Institute for Plant Genomics & Biotechnology, Texas A&M University, U.S.A.; (2) Department of Biochemistry and Biophysics, Institute for Plant Genomics & Biotechnology, Texas A&M University, U.S.A.

Perception of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs) elicits PAMP-triggered immunity (PTI) and contributes to plant resistance to pathogen infection. To understand the mechanisms underlying PTI responses, we have performed a genetic screen for the Arabidopsis genes governing immune gene expression (aggie) using transgenic plants carrying a luciferase reporter under the control of the promoter of a PTI marker gene FRK1(pFRK1::LUC). The dominant mutant aggie5 showed the reduced expression of pFRK1::LUC reporter and endogenous PTI marker genes in response to the treatments by multiple PAMPs. The activation of evolutionarily conserved MAP kinase cascades constitutes a convergent step downstream of multiple PRR signaling. However, PAMP-induced MAPK activation remained unaltered in aggie5. PAMP perception triggers a rapid burst of reactive oxygen species (ROS), which was reduced in aggie5. The data suggest that AGGIE5 regulates a subset of PTI outputs. Consistent with the reduced PTI responses, the aggie5 mutant showed increased susceptibility against a virulent bacterial pathogen Pseudomonas syringae. Map-based cloning coupled with bulk population sequencing revealed that aggie5 carries a mutation in a putative lipase gene (LIP) linked to the reduced luciferase activity. Overexpression of the mutant form of LIP (LIPaggie5) in wild-type pFRK1::LUC plants reduced multiple PTI responses, mimicking the aggie5 mutant. We hypothesize that LIPaggie5 dominantly suppresses the function of multiple LIP family members and negatively regulates PTI responses in Arabidopsis. In-depth biochemical analysis of the lipase activity, lipid metabolomic profiling and integration with the PTI signaling network are ongoing.

Abstract Number: P17-562
Session Type: Poster