Induction of innate immune responses by flagellin from the intracellular bacterium, ‘CandidatusLiberibacter solanacearum’

BMC Plant Biology

Research Article

Hong Lin¹  Ed Stover²  Yongping Duan²  Guixia Hao²  Marco Pitino²  Fang Ding² 

[1] USDA-ARS, San Joaquin Valley Agricultural Sciences Center, 93648, Parlier, CA, USA;USDA-ARS, U. S. Horticultural Research Laboratory, 2001 South Rock Rd, 34945, Fort Pierce, FL, USA;

关键词: Candidatus Liberibacter solanacearum;    Flagellin;    Flg22;    Cell death;    Reactive oxygen species;    Gene expression;   

DOI  :  10.1186/s12870-014-0211-9

 received in 2013-11-26, accepted in 2014-07-24,  发布年份 2014

来源: Springer

【 摘 要 】

Background‘Candidatus Liberibacter solanacearum’ (Lso) is a phloem-limited alphaproteobacterium associated with the devastating zebra chip disease of potato (Solanum tuberosum). Like other members of Liberibacter, Lso-ZC1 encodes a flagellin domain-containing protein (FlaLso) with a conserved 22 amino-acid peptide (flg22Lso). To understand the innate immune responses triggered by this unculturable intracellular bacterium, we studied the pathogen-associated molecular patterns (PAMPs) that triggered immunity in Nicotiana benthamiana, using the flg22Lso peptide and the full length flaLso gene.ResultsOur results showed that the expression of flaLso via Agrobacterium-mediated transient expression induced a slow necrotic cell death in the inoculated leaves of N. benthamiana, which was coupled with a burst of reactive oxygen species (ROS) production. Moreover, the expression of several representative genes involved in innate immunity was transiently up-regulated by the flg22Lso in N. benthamiana. The FlaLso, however, induced stronger up-regulation of these representative genes compared to the flg22Lso, especially that of flagellin receptor FLAGELLIN SENSING2 (FLS2) and respiratory burst oxidase (RbohB) in N. benthamiana. Although neither cell death nor ROS were induced by the synthetic flg22Lso, a weak callose deposition was observed in infiltrated leaves of tobacco, tomato, and potato plants.ConclusionThe flagellin of Lso and its functional domain, flg22Lso share characteristics of pathogen-associated molecular patterns, and trigger unique innate immune responses in N. benthamiana. Slow and weak activation of the innate immune response in host plants by the flagellin of Lso may reflect the nature of its intracellular life cycle. Our findings provide new insights into the role of the Lso flagellin in the development of potato zebra chip disease and potential application in breeding for resistance.

【 授权许可】

Unknown   
© Hao et al. 2014. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.