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Title: Reduced susceptibility to Xanthomonas citri in transgenic citrus expressing the FLS2 receptor from Nicotiana benthamiana

Author
item Hao, Guixia
item Pitino, Marco
item Duan, Ping
item Stover, Eddie

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2015
Publication Date: 2/1/2016
Citation: Hao, G., Pitino, M., Duan, Y., Stover, E. 2016. Reduced susceptibility to Xanthomonas citri in transgenic citrus expressing the FLS2 receptor from Nicotiana benthamiana. Molecular Plant-Microbe Interactions. 29:132-142.

Interpretive Summary: Use of biotechnology to express resistance genes provides a novel approach to enhance plant immunity and broad-spectrum disease resistance. The citrus canker disease is one of the important diseases damaging citrus production worldwide. In this study, we used biotechnology to express a gene in canker-susceptible citrus from a plant that is not canker-susceptible. The gene used produces a receptor that recognizes part of the canker bacterium and triggers non-host resistance. Our study showed that the citrus producing the new receptor was canker resistant and displayed a range of resistance responses. The results suggest that canker susceptible Citrus genotypes lack the receptor that recognizes the canker bacterium and that resistance of these genotypes can be enhanced by expressing the receptor from a resistant species.

Technical Abstract: Overexpression of plant pattern-recognition receptors (PRRs) by genetic engineering provides a novel approach to enhance plant immunity and broad-spectrum disease resistance. The citrus canker disease associated with Xanthomonas citri is one of the important diseases damaging citrus production worldwide. In this study, we cloned FLS2 receptor gene from N. benthamiana cDNA and inserted it into the binary vector pBinPlus/ARS for citrus transformation. The integration of transgene in transgenic lines was confirmed by Polymerase chain reaction (PCR) and the gene expression of NbFLS2 was compared by reverse transcriptase quantitative PCR (RT-qPCR). Reactive oxidase species (ROS) production in response to flg22Xcc of X. citri (Xcc) was detected in transgenic Hamlin but not in non-transformed controls. Much lower ROS production was detected from nontransformed Hamlin and Carrizo seedlings challenged with flg22Xcc. Transgenic lines expressing NbFLS2 were selected and evaluated for resistance to canker induced by X. citri 3213. Our results showed that the integration and expression of the NbFLS2 gene in citrus can increase canker resistance when challenged with spray inoculation. The results suggest that canker susceptible Citrus genotypes lack strong basal defense induced by Xcc flagellin and the resistance of these genotypes can be enhanced by transgenic expression of the flagellin receptor from a resistant species.