两套组氨酸代谢系统在水稻细菌性条斑病菌致病中的功能与机制

由稻黄单胞菌稻生致病变种（Xanthomonas oryzae pv. oryzicola, Xoc）引起的细菌性条斑病是水稻上一种重要的细菌病害。申请者在前期工作中已明确DSF（Diffusible Signal Factor）信号系统调控了Xoc在水稻上的致病性,并鉴定了DSF信号途径下游的5个致病因子。其中，HshB与Xoc已知的组氨酸代谢途径中一个保守的组份HutI具有同样的结构域，但两者没有序列同源性。近期结果表明：在Xoc中，DSF信号系统通过一种间接机制来调控下游hshB和HutI的转录；hshB和hutI均调控组氨酸代谢和致病性。本项目以hshB和HutI为研究对象，从上游层面研究DSF信号系统调控两者转录的分子机制，并明确调控机制的异同点；从下游层面解析两者在调控组氨酸代谢和致病性方面的关系。研究结果将揭示黄单胞菌中DSF信号途径调控组氨酸代谢和致病性的一种新机制。

Bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola is an important bacterial rice disease. In previous works, we have addressed the critical roles of DSF signal system in the virulence of Xoc, and identified five DSF-controlled and uncharacterized virulence factors.Of these, HshB shared a same and conserved domain with HutI, a critical component of the known histidine degradation system in Xoc, however, no similarity was observed in sequence between each other. Furthermore, our recent results, on one hand, showed that DSF signal system used an indirect and uncharacterizaed mechanism(s) to modulate the expression of hshB and HutI at transcriptional level; on the other hand, revelad that both hshB and hutI were involved in histidine degradation and virulence in Xoc.In the present study, on one hand, we aim to investigate and compare the genetic mechanisms of DSF signal system in the transcriptional regulation of hshB and hutI; on the other hand, we are interested to address the relationship(s) between hshB and HutI in modulating histidine degredation and virulence in Xoc. Our results will reveal a new mechanism of DSF signal pathway in the modulation of histidine degradation and virulence in Xanthomonas.