RNA沉默是一种重要的植物防卫机制。植物病毒通常进化出一类称为RNA沉默抑制子的蛋白，干扰寄主的miRNA与siRNA途径，抑制RNA沉默。但是，病原细菌如何抑制寄主RNA沉默尚不清楚。迄今为止，细菌编码的RNA沉默抑制子仅发现于丁香假单胞菌番茄变种，且仅作用于miRNA途径。柑橘黄龙病菌亚洲种(CLas)为革兰氏阴性菌，是引发我国柑橘黄龙病的主要病原。项目前期研究发现：CLas编码一种非典型分泌蛋白ncsp11，抑制siRNA介导的RNA沉默。因而，ncsp11可能代表了一类此前未知的细菌RNA沉默抑制子。本项目基于此发现展开，拟解析ncsp11抑制RNA沉默的分子基础，分析其对寄主小RNA生物合成的影响，鉴定与ncsp11特异互作的寄主蛋白，阐释蛋白互作在CLas侵染、定殖过程中的作用。预期结果将揭示病原细菌抑制寄主RNA沉默的新机制，同时为阐明CLas致病机理提供新依据。

RNA silencing is a fundamental defense mechanism in plants. Plant viruses usually evolve suppressor of RNA silencing that interfere with miRNA and siRNA pathways to suppress RNA silencing. However, it is remain uncertain how pathogenic bacteria challenge the host RNA silencing. So far, the bacterial suppressor of RNA silencing (BSR) has only been identified in Pseudomonas syringae pv. tomato, and target only the host miRNA pathway. ‘Candidatus Liberibacter asiaticus’ (CLas) belongs to Gram-negative α-proteobacteria, and is the causal agent of citrus Huanglongbing (HLB) prevalent in China. Recently, we identified that a CLas-encoded non-classically secreted protein is able to inhibit siRNA-mediated RNA silencing, indicating a novel BSR. Accordingly, in this study, a series of experiments will be performed to investigate the molecular basis of ncsp11 suppressing RNA silencing, dissect the effect of ncsp11 on sRNA biogenesis, screen the host protein(S) interacting with ncsp11, and characterize the biological significance of the ncsp11-host protein(s) interacting. The resulting data will not only disclose a novel mechanism of pathogenic bacteria interfering with the host RNA silencing, but provide new evidence for elucidate the pathogenesis of CLas.