A natriuretic peptide molecule from Vigna angularis, VaEG45, confers rust resistance by inhibiting fungal development

Novel function and mechanism of a PNP molecule VaEG45 from adzuki bean involved in plant immunity. Plant natriuretic peptides (PNPs) can affect a broad spectrum of physiological responses in plants acting as peptidic signaling molecules. However, PNPs may play additional roles in plant immunity. Our previous transcriptome data of adzuki bean (Vigna angularis) in response to Uromyces vignae infection revealed association of PNP-encoding gene VaEG45 with U. vignae resistance. To determine the function of VaEG45 in disease resistance, we cloned the 589 bp nucleotide sequence of VaEG45 containing 2 introns, encoding a putative 13.68 kDa protein that is 131 amino acids in length. We analyzed expression in different resistant cultivars of V. angularis and found significant induction of VaEG45 expression after U. vignae infection. Transient expression of VaEG45 improved tobacco resistance against Botrytis cinerea. We next analyzed the mechanism by which VaEG45 protects plants from fungal infection by determination of the biological activity of the prokaryotic expressed VaEG45. The results showed that the fusion protein VaEG45 can significantly inhibit urediospores germination of U. vignae, mycelial growth, and the infection of tobacco by B. cinerea. Further analysis revealed that VaEG45 exhibits β-1, 3-glucanase activity. These findings uncover the function of a novel PNP molecule VaEG45 and provide new evidence about the mechanism of PNPs in plant immunity.