Overexpression of AtPROPEP6 enhances Arabidopsis thaliana resistance to Southern root-knot nematode Meloidogyne incognita - PubMed (original) (raw)

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

Payal Sanadhya et al. Plant Signal Behav. 2026.

Abstract

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 PROPEP_s beyond AtPROPEP1-3 and identify AtPROPEP6 as a paralog contributing to plant defense against nematodes.

Keywords: AtPROPEP6; Meloidogyne incognita; Plant elicitor peptide; plant defenses; root-knot nematode.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.

Figure 1.

Transcriptional regulation of AtPROPEP6 expression suggests an involvement in plant defenses**.** (a) Defense-related Cis-Regulatory Elements (CREs) in the promoter of the AtPROPEP6 gene. The positional distribution of predicted CREs is shown as vertical color-coded bars for individual binding sites (see also Table S2). Red–W box/WRKY binding site; black - other defense-related CREs. (b) Log2 fold change of AtPROPEPs expression in response to ascr#18 treatment. The expression pattern data were obtained from the published RNAseq analysis of Arabidopsis genes induced by ascr#18 treatment (1 µM ascr#18 treatment for 6 hours) -NCBI Bio Project Accession PRJNA550121. Numbers represent averages of 4 biological replicates, _p_-value < 0.05, FDR < 0.05.

Figure 2.

Figure 2.

AtPROPEP6 overexpression increased the basal expression of the AtPR1a marker gene. The relative expression of (a) AtPROPEP6, (b) SA marker genes (AtPRa1, AtPP22B13), and (c) JA marker genes (AtACPL1, AtPR4, AtPDF1.2) in homozygous AtPROPEP6-oe lines (6:2, 6:6, and 6:8) was determined by qRT-PCR. Results are presented as the fold change in relative basal expression compared to non-transgenic control (Col-0). Different letters indicate statistically significant differences among treatments (one-way ANOVA followed by Tukey’s post hoc test; α = 0.05; n = 3).

Figure 3.

Figure 3.

AtPROPEP6 overexpression reduces Arabidopsis susceptibility to M. incognita infection**.** (a) Root penetration assay scored at 3 dpi, and (b_–_d) galling and nematode development assay scored at 28 dpi (including (b) number of galls, (c) total nematode count, and (d) number of females). Nematode infection assays were performed on three transgenic AtPROPEP6-oe lines (6:2, 6:6, and 6:8) and wild-type Col-0 as described in Figure S1. Data points were obtained from two independent experiments (Blocks 1 and 2) with a total of n = 16 (a) and n = 8 (b_–_d) for each line per experiment. Different letters indicate statistically different results between treatments (one-way ANOVA followed by Tukey’s post hoc test p < 0.05).

Figure 4.

Figure 4.

Overexpression of AtPROPEP6 impacts root morphology and bolting. Belowground morphological measurements included (a) root length and (b) number of lateral roots in 14-day-old plants. Aboveground traits were recorded as (c_–_d) leaf area and (e) bolting at 21 days. For (a_–_c), data points were obtained from two independent experiments (Blocks 1 and 2). Different letters indicate significant differences (one-way ANOVA with Tukey's HSD, P < 0.05, n = 10). For (e), lines marked with an asterisk are significantly different from Col-0 control based on Chi-square test with a total of n = 10 for each line per experiment (p < 0.001).

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