Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850.
Department of Plant Pathology, University of Florida, Gainesville, FL 32611.
Phytopathology. 2022 Jan;112(1):145-153. doi: 10.1094/PHYTO-07-21-0301-FI. Epub 2022 Jan 13.
' Liberibacter asiaticus' (CLas), the devastating pathogen related to Huanglongbing (HLB), is a phloem-limited, fastidious, insect-borne bacterium. Rapid spread of HLB disease relies on CLas-efficient propagation in the vector, the Asian citrus psyllid , in a circulative manner. Understanding the intracellular lifecycle of CLas in psyllid midgut, the major organ for CLas transmission, is fundamental to improving current management strategies. Using a microscopic approach within CLas-infected insect midgut, we observed the entry of CLas into gut cells inside vesicles, termed Liberibacter-containing vacuoles (LCVs), by endocytosis. Endocytosis is followed by the formation of endoplasmic reticulum-related and replication permissive vacuoles (rLCVs). Additionally, we observed the formation of double membrane autophagosome-like structure, termed autophagy-related vacuole (aLCV). Vesicles containing CLas egress from aLCV and fuse with the cell membrane. Immunolocalization studies showed that CLas uses endocytosis- and exocytosis-like mechanisms that mediates bacterial invasion and egress. Upregulation of autophagy-related genes indicated subversion of host autophagy by CLas in psyllid vector to promote infection. These results indicate that CLas interacts with host cellular machineries to undergo a multistage intracellular cycle through endocytic, secretory, autophagic, and exocytic pathways via complex machineries. Potential tactics for HLB control can be made depending on further investigations on the knowledge of the molecular mechanisms of CLas intracellular cycle.
‘亚洲韧皮杆菌’(CLas),与黄龙病(HLB)相关的破坏性病原体,是一种局限于韧皮部、苛刻的、昆虫传播的细菌。HLB 疾病的迅速传播依赖于 CLas 在传播媒介亚洲柑橘木虱中以循环方式进行有效的繁殖。了解 CLas 在柑橘木虱中肠内的细胞内生命周期,是改善当前管理策略的基础。我们使用感染了 CLas 的昆虫中肠内的显微镜方法,观察到 CLas 通过内吞作用进入肠细胞内的囊泡,称为含韧皮杆菌的空泡(LCVs)。内吞作用之后,形成与内质网相关的和复制许可的空泡(rLCVs)。此外,我们观察到形成双膜自噬体样结构,称为自噬相关空泡(aLCV)。含有 CLas 的囊泡从 aLCV 中逸出并与细胞膜融合。免疫定位研究表明,CLas 使用内吞作用和外排作用样机制介导细菌入侵和逸出。自噬相关基因的上调表明 CLas 在木虱载体中通过宿主自噬的颠覆来促进感染。这些结果表明,CLas 通过复杂的机制与宿主细胞机制相互作用,通过内吞作用、分泌作用、自噬作用和外排作用途径经历多阶段的细胞内周期。可以根据对 CLas 细胞内周期分子机制的进一步研究,制定 HLB 控制的潜在策略。