Liu Xuelu, Fan Yanyan, Zhang Chao, Dai Meixue, Wang Xuefeng, Li Weimin
Citrus Research Institute, Southwest University, Chongqing, China.
Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.
Front Microbiol. 2019 Jul 24;10:1684. doi: 10.3389/fmicb.2019.01684. eCollection 2019.
" Liberibacter asiaticus" (CLas), one of the causal agents of citrus Huanglongbing (HLB), secretes proteins with functions that are largely unknown. In this study, we demonstrated that CLIBASIA_00460, one of the CLas-encoded Sec-dependent presecretory proteins, might contribute to the phytopathogenicity of CLas. was conserved in CLas strains and expressed at a significantly higher level in citrus than in Asian citrus psyllid. -mediated transient expression in epidermal cells showed that the mature CLIBASIA_00460 (m460) without the putative Sec-dependent signal peptide was localized in multiple cellular compartments including nucleus at 25°C, but that nuclear accumulation was greatly decreased as the temperature rose to 32°C. When overexpressed a (PVX)-based expression vector in , m460 induced no local symptoms, but tiny necrotic spots were scattered on the systemic leaves. However, NLS-m460, which contains the SV40 nuclear localization sequence (NLS) at the N-terminus to promote nuclear import of m460, caused chlorosis and necrosis in the local leaves and severe necrosis in the systemic leaves. Taken together, these data suggest that CLIBASIA_00460 represented a novel virulence factor of CLas, and that nuclear localization of this protein was temperature dependent and positively correlated with its pathogenicity .
亚洲韧皮杆菌（CLas）是柑橘黄龙病（HLB）的致病因子之一，它分泌的蛋白质功能大多未知。在本研究中，我们证明了CLIBASIA_00460是CLas编码的依赖Sec的前分泌蛋白之一，可能对CLas的致病性有贡献。它在CLas菌株中保守，在柑橘中的表达水平显著高于亚洲柑橘木虱。在烟草表皮细胞中进行的病毒介导的瞬时表达表明，没有假定的依赖Sec信号肽的成熟CLIBASIA_00460（m460）在25°C时定位于包括细胞核在内的多个细胞区室，但随着温度升至32°C，核积累大大减少。当在烟草中基于马铃薯X病毒（PVX）的表达载体上过表达m460时，未诱导局部症状，但在系统叶上散布有微小的坏死斑。然而，在N端含有SV40核定位序列（NLS）以促进m460核输入的NLS-m460，在局部叶片中引起黄化和坏死，在系统叶片中引起严重坏死。综上所述，这些数据表明CLIBASIA_00460是CLas的一种新型毒力因子，该蛋白的核定位依赖温度且与其致病性呈正相关。
