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Abstract

Bacterial blight (BB) of rice is caused by bacterium Xanthomonas oryzae pv oryzae (Xoo), giving significant yield loss to the crop. The pathogen injects its Transcription Activation-Like Effectors (TALEs) into host cells, where the TALEs bind to the effector binding elements (EBEs) in host gene promoters, inducing susceptibility (S) or resistance (R) genes, thus causing disease or resistance. A major class of Xoo-induced S genes in rice encodes cellular sucrose transporters, referred to as the OsSWEET genes family. Three OsSWEET genes—OsSWEET11, OsSWEET13, and OsSWEET14—are distinctly induced by different Xoo strains from diverse geographical regions of the world, via their cognate TALEs, to cause BB in the field. Begami (JP-5) is a farmer-maintained BB-susceptible Japonica-type rice landrace from northern Pakistan, locally known as Begami and Garhla in different regions. However, the OsSWEET gene induced by Pakistani Xoo strains in Begami rice is not known. In the current study, OsSWEET11 was identified as specifically induced by KP-3, a representative Xoo strain from the Himalayan foothills, in Begami. Further, promoter analysis of OsSWEET11 in the variety identified intact EBE sequence specific to TALE PthXo1 of Xoo. The study suggests that Begami offers OsSWEET11 as a major S gene target for BB disease. The study further suggests that KP-3 harbors PthXo1, a cognate TALE of OsSWEET11, as its major virulence effector for the disease. Characterizing Xoo strains, and rice cultivars resistant or susceptible to these strains, is a fundamental step to understanding the Xoo-rice coevolution and developing race-specific resistance strategies in a specific region. The present study provides a baseline to develop a resistant Begami cultivar either by breeding or targeted editing of OsSWEET11 promoter.

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