Phosphatidylinositol-phospholipase C2 regulates pattern-triggered immunity in Nicotiana benthamiana.

Phospholipid signaling plays an important role in plant immune responses against phytopathogenic bacteria in Nicotiana benthamiana. Here, we isolated two phospholipase C2 (PLC2) orthologs in the N. benthamiana genome, designated as N. benthamiana PLC2-1 and 2-2. Both NbPLC2-1 and NbPLC2-2 were expressed in most tissues and induced by infiltration with bacteria and flg22. NbPLC2-1 and NbPLC2-2 (NbPLC2s) double-silenced plants showed a moderately reduced growth phenotype. The induction of the hypersensitive response was not affected, but bacterial growth and the appearance of bacterial wilt were accelerated in NbPLC2s-silenced plants challenged with Ralstonia solanacearum that was compatible with N. benthamiana. NbPLC2s-silenced plants showed reduced expression levels of NbPR-4, a marker gene for jasmonic acid signaling, and decreased jasmonic acid and jasmonoyl-L-isoleucine contents after inoculation with R. solanacearum. The induction of pathogen-associated molecular pattern-triggered immunity (PTI) marker genes was reduced in NbPLC2s-silenced plants after infiltration with R. solanacearum or Pseudomonas fluorescens. Accordingly, the induced resistance by flg22 was compromised in NbPLC2s-silenced plants. In addition, flg22-induced PTI marker genes' expression, oxidative burst, stomatal closure and callose deposition were all reduced in NbPLC2s-silenced plants. Thus, NbPLC2s might have important roles in pre- and post-invasive defenses, namely in PTI induction.