The role of PRLIP2 in the defence and growth of Arabidopsis Insertional mutagenesis of PRLIP2 gene alters hormone balance and defence responses in Arabidopsis

Previously, our group identified a novel gene family responsible for encoding pathogenesis-related lipase-like proteins (PRLIPs) through a differential screening process involving Arabidopsis plants that were pre-treated with the resistance-inducing compound β-aminobutyric acid (BABA). In the present study we have characterized two independent mutant lines of Arabidopsis possessing T-DNA insertion in their PRLIP2 gene. Both prlip2 mutant lines displayed enhanced susceptibility to the virulent hemibiotrophic bacterial pathogen Pseudomonas syringae pv. DC3000 and were incapable of expressing BABA-induced resistance. This increased susceptibility was associated with a reduced expression of the PTI marker genes FRK1 (FLG22-INDUCED RECEPTOR KINASE1) and NHL10 (NDR1/HIN1-like 10) and a low expression of PR1 (PATHOGENESIS-RELATED PROTEIN 1), a marker gene for salicylic acid (SA) signalling. In contrast, the jasmonic acid (JA)/ethylene (ET) signalling pathway was up-regulated in the mutants. In addition, the mutation in the PRLIP2 gene resulted in increased plant growth and augmented auxin content. Furthermore, the elevated auxin levels in the mutant lines might counteract the SA responses, consequently up-regulating jasmonic acid (JA) signalling in these mutants. While the significant role of PRLIP2 as a negative regulator of auxin in plant defence responses has been clearly demonstrated, the precise molecular mechanisms underlying this phenomenon, which leads to divergent hormonal balance, remain incompletely elucidated.