Overexpression of AtPROPEP6 enhances Arabidopsis thaliana resistance to Southern root-knot nematode Meloidogyne incognita

Plant elicitor peptides (Peps), derived from PROPEP protein precursors, are stress-induced signaling molecules that enhance plant immunity. While previous studies of Pep-mediated immune signaling in Arabidopsis thaliana have focused on the roles of AtPROPEP1-3 genes in bacterial and fungal resistance, this study identifies the AtPROPEP6 gene as a contributor to defense against the Southern root-knot nematode (Meloidogyne incognita). In silico promoter analysis revealed enrichment of W box motifs, suggesting potential regulation by WRKY transcription factors associated with plant immune responses. Unlike other PROPEP gene family members, AtPROPEP6 shows specific upregulation in response to ascr#18, a nematode-derived molecular pattern, but not to other pathogen elicitors. Transgenic constitutive overexpression of AtPROPEP6 in A. thaliana significantly reduced gall formation and total nematode numbers and delayed nematode development. These phenotypes correlated with AtPROPEP6 transcript abundance in three independent transgenic lines and were accompanied by elevated basal AtPR1a expression. Although AtPROPEP6-overexpressing plants exhibited shorter roots, the extent of root length reduction did not align with transgene expression levels, and the number of root tips available for infection remained unchanged. Our findings expand the repertoire of defense-associated A. thaliana PROPEPs beyond AtPROPEP1-3 and identify AtPROPEP6 as a paralog contributing to plant defense against nematodes.