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Front Microbiol. 2018 Apr 27;9:847. doi: 10.3389/fmicb.2018.00847. eCollection 2018.

Stomatal Closure and SA-, JA/ET-Signaling Pathways Are Essential for Bacillus amyloliquefaciens FZB42 to Restrict Leaf Disease Caused by Phytophthora nicotianae in Nicotiana benthamiana.

Wu L1,2, Huang Z1, Li X1,2, Ma L1,2, Gu Q1,2, Wu H1,2, Liu J3, Borriss R4,5, Wu Z6, Gao X1,2.

Author information

1
College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
2
Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Education, Nanjing, China.
3
Chongqing Key Laboratory of Economic Plant Biotechnology, College of Forestry & Life Science, Chongqing University of Arts and Sciences, Yongchuan, China.
4
Nord Reet UG, Greifswald, Germany.
5
Fachgebiet Phytomedizin, Institut für Agrar-und Gartenbauwissenschaften, Humboldt-Universität zu Berlin, Berlin, Germany.
6
College of Horticulture, Nanjing Agricultural University, Nanjing, China.

Abstract

Bacillus amyloliquefaciens FZB42 is a plant growth-promoting rhizobacterium that induces resistance to a broad spectrum of pathogens. This study analyzed the mechanism by which FZB42 restricts leaf disease caused by Phytophthora nicotianae in Nicotiana benthamiana. The oomycete foliar pathogen P. nicotianae is able to reopen stomata which had been closed by the plant innate immune response to initiate penetration and infection. Here, we showed that root colonization by B. amyloliquefaciens FZB42 restricted pathogen-mediated stomatal reopening in N. benthamiana. Abscisic acid (ABA) and salicylic acid (SA)-regulated pathways mediated FZB42-induced stomatal closure after pathogen infection. Moreover, the defense-related genes PR-1a, LOX, and ERF1, involved in the SA and jasmonic acid (JA)/ethylene (ET) signaling pathways, respectively, were overexpressed, and levels of the hormones SA, JA, and ET increased in the leaves of B. amyloliquefaciens FZB42-treated wild type plants. Disruption of one of these three pathways in N. benthamiana plants increased susceptibility to the pathogen. These suggest that SA- and JA/ET-dependent signaling pathways were important in plant defenses against the pathogen. Our data thus explain a biocontrol mechanism of soil rhizobacteria in a plant.

KEYWORDS:

ABA; Bacillus amyloliquefaciens FZB42; ISR; Nicotiana benthamiana; stomata

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