Chitinase Gene And ¦Â-1, 3 - Glucanase Gene Transgenic Rice Disease Resistance Research

Fungal rice sheath blight (Rhizoctonia solani) is one of the most destructive diseases in rice, which often causes huge loss of grain production in China. There is no genetic source for disease resistance to this pathogen, neither good tool to control this disease. We transferred a double-gene expression cassette with the rice chitinase gene and the alfalfa P -1, 3-glucanase gene to japonica rice, Taipei 309, and obtained transgenic lines resistant to R. solani.1 . The rice basic chitinase gene RCH10ya,s expressed under the control of its native promoter and the cauliflower mosaic virus (CaMV)35S enhancer, the alfalfa acidic β-1, 3-glucanase, AGLU, was expressed under the control of the CaMV35S double promoter. Both expression structures were tandemly inserted in the transformation vector, pBHOl, resulting in the plasmid pZlOO. pZlOO was transformed into rice (Oryza. saliva. L. ssp. japonica. cv. Taipei309) by agrobacterium tumefacies-mediated and biolistic bombardment transformations. Independent 13 and 5 transformants were obtained from the transformation methods, respectively, and were shown to contain the double-gene expression trasgene by PCR analysis.2 . Segregation of the T1 progenies of the transgenic lines was analyzed by PCR analysis. Results showed that the inheritance of the Tl progenies was complex.3 . Genomic DNA Southern blot analysis was conducted, which indicated that the expression cassette had integrated into the rice genome.4. Northern blotting analysis with the RCH10 and AGLU probes revealed expression variation among these transformants on transcription levels.Similar expression patterns were observed in both RCH10 and AGLU transcripts from the same individuals.5 . Disease resistance to R. solani was evaluated in the transgenic plants. It was demonstrated that the Z100 rice exhibited enhanced resistance to R. solani, and resistance levels were, somehow, related to expression levels of the transgene, indicating that disease resistance is transgene expression dose-dependent. Two independent lines with high disease resistance as well as high expression levels of RCH10 and AGLUwere selected for the further studies and molecular breeding for sheath blight resistance. Results presented here demonstrates that disease resistance can beachieved by co-expressing two or more plant defense genes, where geneticsource of disease resistance is simple invaluable.