Optimization Of The Tissue Culture System For Indica Rice And Functional Characterization Of Defense-responsive Gene 22E6EI14 In Rice

Rice bacterial blight, caused by Xanthomonas oryzae pv. Oryzae (Xoo), is one of the most devastating diseases in rice production worldwide. Gene transfer technology, as a powerful and direct tool to minimize the loss caused by plant diseases, has been getting more and more attention in resent years. Up to now, at least eight rice resistance genes, Xa1, Xa2, Xa3, Xa4, xa5, Xa10, xa13, and Xa21, for bacterial blight resistance have been introduced into rice variety IR24 to form a set of indica near-isogenic lines. In this lab, two bacterial blight resistance genes, Xa4 and xa13, have been targeted to DNA fragments from two near-isogenic lines with the genetic background of IR24 and a great number of resistance-responsive genes have also been identified from the same sets of rice lines. However, the lack of a successful tissue culture system based on these indica lines is still a major obstacle to functional complementary test of these candidate genes. Therefore, the establishment of effecient tissue culture system for the near-isogenic lines with an IR24 background will greatly facilitate molecular characterization of the R genes for bacterial blight resistance and clarification of the interaction between the R genes. On the other hand, IR24 is also one parent of some widely cultivated varieties worldwide, especially in Southeast Asia or South Asia. Genetic improvement of important rice qualities by way of gene transfer technology will also be benefited by this tissue culture system.By manipulating plant growth regulators (PGRs), organic components and salts within the culture media, we established two media for callus induction and subculture, respectively, in tissue culture of indica rice. The modified media could guarantee the production and proliferation of a great number of embryogenic calli with high regeneration capacity from mature seeds of different indica rice varieties, IRBB13, IRBB10, IRBB4, IR24, Minghui63, Zhenshan97 and 93-11. The calli obtained from this system should be ideal material for Agrobacterium-mediated transformation. Futhermore, on the basis of the composition of the induction and subculture media optimized in this study, the media for pre-culture, co-culture, and selection that were subsequent steps in Agrobacterium-mediated transformation of rice were also developed. With these media and the transformation protocols developed by Lin yongjun, we have succeeded in the efficient production of transgenic plants from rice line IRBB13.On the other hand, Chu zhaohui in this lab isolated a gene 22E6EI14 from Minhui 63. Expression of the 22E6EI14 was induced in IRBB13 after inoculation with an incompatible Xoo strain PXO99, but not in the susceptible line IR24. With the results above, Chu zhaohui supposed that 22E6EI14, as a defense-related gene, may be involved...