The Function Of Small Heat Shock Protein SHSP17.5and Heat Shock Factors In Resistance To Bacterial Blight In Rice

The bacterial blight caused by the phytopathogenic bacterium Xanthomonas oryzae pv. oryzae (Xoo), is one of the most devastating diseases in rice, which may cause great loss of rice yield and even lead to lose production completely. With the directional selection between rice and Xoo, the resistance of the original rice varieties was gradually lost. Oryza meyeriana L. is almost immune to Xoo. The new Xoo-resistant germplasm SH5was obtained through somatic hybridization with the wild rice species Oryza meyeriana L. as the donor.By whole genomic microarray analysis, up-regulated OssHSP17.5was screened out based on the expression level in resistant variety SH5after inoculated with Zhe173. The small heat shock proteins (sHSPs), which are ubiquitous stress proteins, can prevent irreversible aggregation of denatured proteins. Detailed studies have established that sHSPs are accumulated in response to a wide range of stresses, including heat, cold, drought, and pathogen attack. The aim of this paper is to study the roles of OssHSP17.5in the resistance to Xoo in rice.The thesis mainly includes three parts. Firstly, the over-expressing and gene-silence vector were constructed, then were introduced into rice variety Nipponbare and SH5, respectively. Secondly, the resistance of the transgenic rice was analyzed. Thirdly, the expression patterns of12heat shock factors(OsHsfs) in response to Xoo were compared between the resistant and susceptible rice. The results are summarized as follows:1. The expression of OssHSPl7.5in resistant and susceptible rice was analyzed by real-time quantitative PCR. The results showed that the expression of OssHSP17.5in the leaves of resistant variety SH5was up-regulated significantly than that of susceptible variety8411. Both over-expressing and gene silence vectors were constructed, and introduced into susceptible variety Nipponbare and resistant variety SH5, respectively. Transgenic rice seedlings were obtained.2. The average lesion length of OssHSP17.5-overexpressing transgenic seedlings was significantly shorter than that of wild-type plants when the leaves were inoculated with Zhe173. The gene silence transgenic rice was the opposite. The pathogenic bacteria grew more slowly in OssHSP17.5-overexpressing transgenic seedlings than in wild-type plants after inoculation, and the content of bacteria was lower in OssHSP17.5-overexpressing transgenic seedlings. Five pathogenesis related protein genes (PR1α, PR1b, PR2, PR4and PR6) and a transcription factor WRKY45were up-regulated significantly by Zhe173inoculation in OssHSPl7.5-overexpressing transgenic seedlings than in wild-type plants.3. After the leaves of resistant variety SH5and susceptible variety8411were inoculated with Zhe173, the expression of12OsHsfs was analyzed by using real-time quantitative PCR. The results showed that OsHsfA2a, OsHsfA2c, OsHsfB2b and OsHsfB2c were significantly increased in SH5than in8411. The functions of four OsHsfs on Xoo resistance are worth further investigation.