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Abstract

Plant cell surface receptors sense microbial pathogens by recognizing microbial structures called pathogen or microbe-associated molecular patterns (PAMPs/MAMPs). There are two major types of plant pattern recognition receptors: 1. Leucine-rich repeat receptor proteins (LRR-RP) and leucine-rich repeat receptor kinases (LRR-RK) and 2. Plant receptor proteins and receptor kinases carrying ectopic lysin motifs (LysM-RP and LysM-RK). Although many studies focused on the signal pathways triggered by these receptors individually, the exact overlap and the differences, respectively, between these pathways remain unknown. We use three different PAMPs, flg22, nlp20, chitin (chitohexaose), and their corresponding receptor types, FLS2 (RLK), RLP23 (RLP), CERK1 (LYM-RK) for our comparisons. By systematic analyses of defense responses such as transcriptome changes, ROS burst and accumulated hormones, we found that flg22 triggers faster and stronger early responses, and also causes more extensive transcriptome changes. On the other hand, only nlp20-treatment results in high amounts of salicylic acid and camalexin accumulation. After mutant lines screening we found that BIK1 may play different roles in signaling after flg22 and nlp20 treatments. We will present a more complete picture of PAMP-triggered immunity and to discover new key components participating in plant immunity.