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Poster: Molecular & Cellular Plant-Microbe Interactions: Biotechnology


Overexpression of a modified plant thionin enhances disease resistance to citrus canker and Huanglongbing (HLB, citrus greening)
G. HAO (1), E. stover (1) (1) usda/ars/hrl, U.S.A.

Huanglongbing (HLB or citrus greening disease) caused by Candidatus Liberibacter asiaticus (Las) is a great threat to the US citrus industry. Citrus canker is also an economically important disease associated with a bacterial pathogen (Xanthomonas citri). In this study, we characterized endogenous citrus thionins and investigated their expression in different citrus tissues. We aim to develop citrus resistant to both HLB and citrus canker through expression of modified plant thionin. In order to improve effective for disease resistance, we modified and synthesized the sequence encoding plant thionin and cloned into binary vector pBinPlus/ARS. The construct was introduced into Agrobacterium strain EHA105 and used for citrus transformation. Transgenic Carrizo plants expressing the modified plant thionin were successfully generated through Agrobacterium-mediated transformation. Transgenic Carrizo plants expressing the modified thionin gene were challenged with X. citri 3213 at various concentrations, and showed a significant reduction in canker symptoms and a decrease in bacterial growth compared to nontransgenic plants. Furthermore the transgenic citrus plants were challenged with HLB via graft inoculation. The results showed significant decrease in the Las titer in transgenic Carrizo compared with nontransgenic plants. These data, thus, provide a promising approach to engineering citrus disease resistance against HLB and canker.