| Summary: | 碩士 === 國立中興大學 === 生物化學研究所 === 99 === Xanthomonas is a Gram-negative bacterial pathogens. It can infect not only a variety of important economic crops, but also the model plant Arabidopsis thaliana. Xanthomonas use the type III secretion system to deliver the type III effector proteins into the plant cells to help bacteria multiply. However, the functions of most effector proteins are still unknown. Here XVE:xopd8004 transgenic plants showed etiolated phenotypes with long hypocotyls and chlorophyll-less cotyledons. This phenomenon is the same with the deficiency of photomorphogenesis. So far, the related researches of XopD largely confined to that of X. campestris pv. vescatoria 85-10. The protein size of XopD85-10 is 760 amino acids. Although XopD8004 only has 442 amino acids,
Nevertheless XopD8004 can specifically recognize and hydrolyze the SUMO-modified proteins in vitro and in vivo. Using a pull-down assay, XopD8004 was found to interact with HFR1, a transcription factor in light signaling transduction pathway. Moreover, using confocal laser scanning, the fluorescent signal of XopD8004-YFP was observed in the nucleus as foci and co-localized with HFR1-CFP. As a result, we proposed that HFR1 is the cellular target protein of XopD8004 and may be involved in the plant immune response. Here, we also established a protocol to identify ADP ribosyltransferases (ADP-RTs) activity of type III effectors. In P. syringae, three type III effectors have been suggested to have ADP-RTs activities including HopO1-1, HopO1-2 and HopU1. According to the method, we have observed ADP-RTs activity of HopU1. Although X. axonopodis XopAI306 has been suggested to have similar domain as HopO1-1, no enzyme activity was observed using our method.
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