Bacterial and plant natriuretic peptides improve plant defense responses against pathogens

FICARRA, FLORENCIA A.; GOTTIG, NATALIA; GARAVAGLIA, BETIANA S.; GRANDELLIS, CAROLINA; OTTADO, JORGELINA

MOLECULAR PLANT PATHOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2018 vol. 19 p. 801 - 811

1464-6722

Plant natriuretic peptides (PNPs) are implicated in the regulation of ions and water homeostasis, and their participation in the plant immune response has been also proposed. Xanthomonas citri subsp. citri contains a gene encoding a PNP-like protein (XacPNP) that has no homologues in other bacteria. XacPNP mimics its Arabidopsis thaliana homolog AtPNP-A by modifying host responses to create favorable conditions for pathogen survival. However, the ability of XacPNP to induce plant defense responses was never investigated. Here, and to further study the role of XacPNP in vivo, A. thaliana lines over-expressing XacPNP and also, lines over-expressing AtPNP-A or AtPNP-A deficient plants were generated. Plants over-expressing XacPNP as well as AtPNP-A showed larger stomatal aperture and were more resistant to saline or oxidative stress than PNP deficient lines. First, and to further study the role of PNP in biotic stress responses, A. thaliana leaves were infiltrated with pure recombinant XacPNP and showed enhanced expression of genes related with the defense response and a higher resistance to pathogen infections. Moreover, AtPNP-A expression increased in A. thaliana upon Pseudomonas syringae pv. tomato (Pst) infection. These evidences led us to analyze the transgenic plants responses to pathogens. Plants over-expressing XacPNP and AtPNP-A were more resistant to Pst infection compared to control plants, while PNP deficient plants were more susceptible and showed a stronger HR when challenged with a non-host bacteria. Therefore, XacPNP, acquired by horizontal gene transfer, is able to mimic PNP functions even in the increase of plant defense responses.