噬菌体溶源/溶菌周期转换是自然界重要的生物学现象，但目前并不清楚何时何种条件下会发生周期转换。申请人所在课题组前期已发现传统的丝裂霉素C无诱导效果，而外源噬菌体刺激能诱导10株水稻白叶枯病菌噬菌体溶源/溶菌周期的转换，为进一步搞清楚外源刺激诱导溶源/溶菌周期转换的机制，本项目拟在前期已分离纯化获得28个外源刺激诱导白叶枯病菌溶源/溶菌周期转换所释放的前噬菌体，透射电镜观察结合基因组酶切分析排除外源噬菌体的基础上，首先通过测定水稻白叶枯病菌诱导释放的烈性噬菌体基因组，以进一步鉴定噬菌体溶源/溶菌周期的转换；其次qPCR测定白叶枯病菌编码前噬菌体基因的表达情况，以鉴定溶源/溶菌周期转换的相关基因；最后构建溶源/溶菌周期转换相关基因的突变体和回补体，测定和比较其与野生型的差异，以明确水稻白叶枯病菌噬菌体溶源/溶菌转换的机制，为通过调控溶源/溶菌周期转换来生态控制水稻白叶枯病提供理论依据。

Lysogenic/lytic cycle switch in bacteriophage is important. However, it is still not clear about the timing and factors that can induce the cycle switch. Previous study within our group shows that the cycle switch of 10 strains of Xanthomonas oryzae pv. oryzae can be activated upon the addition of exogenous phages, but cannot be induced by using the traditional mitomycin C. Here, to elucidate the mechanism of lysogenic/lytic cycle switch in bacteriophage of X. oryzae pv. oryzae, we collected and purified 28 prophages released upon exogenous insult. Further transmission electron microscope technique and enzymic fingerprinting of phage genome were applied to verify the induced prophages. Then the whole genome sequence of the released lytic phages will be identified to support the lysogenic/lytic cycle switch. Moreover, qPCR will be applied to determine the gene expressions, which are predicted to be involved in the lysogenic/lytic cycle switch in bacteriophage of X. oryzae pv. oryzae. Furthermore, the mutant and complementary strains will be constructed and compared with the wild type to determine the characterizations, which are related to the cycle switch upon exogenous insults. Accordingly, the mechanism of lysogenic/lytic cycle switch will be elucidated. Taken together, understanding on mechanism for cycle switch in bacteriophage of X. oryzae pv. oryzae induced by exogenous insult will contribute greatly to its biological control.