Transcriptomic profiling uncovers novel players in innate immunity in Arabidopsis thaliana

In this research a high-throughput RNA sequencing based transcriptome analysis technique (RNA-Seq) was used to evaluate differentially expressed genes (DEGs) in the wild type Arabidopsis seedling in response to flg22, a well-known microbe-associated molecular pattern (MAMP), and AtPep1, a well-known peptide representing an endogenous damage-associated molecular patterns (DAMP). The results of our study revealed that 1895 (1634 up-regulated and 261 down-regulated) and 2271 (1706 up-regulated and 565 down-regulated) significant differentially expressed genes in response to flg22 and AtPep1 treatment, respectively. Among significant DEGs, we observed that a number of hitherto overlooked genes have been found to be induced upon treatment with either flg22 or with AtPep1, indicating their possible involvement in innate immunity. Here, we characterized two of them, namely PP2-B13 and ACLP1. pp2-b13 and aclp1 mutants showed an increased susceptibility to infection by the virulent pathogen Pseudomomas syringae pv tomato mutant hrcC-, as evidenced by an increased growth of the pathogen in planta. Further we present evidence that the aclp1 mutant was deficient in ethylene production upon flg22 treatment, while the pp2-b13 mutant, was deficient in ROS production. The results from this research provide new information to a better understanding of the immune system in Arabidopsis.