Pseudomonas syringae pv. actinidiae (Psa) causes destructive kiwifruit bacterial canker by invading vascular tissues across multiple plant organs. However, the cellular mechanism underlying its systemic transmission and cell-to-cell movement within these specialized vascular conduits remains unclear. In this study, a Psa-GFP strain and various microscopic techniques were used to investigate the interaction between kiwifruit and Psa. Our results reveal that Psa strategically exploits host vascular conduits for systemic movement, with the xylem vessel being the predominant avenue. In the phloem, Psa exhibits adaptive alteration in bacterial shape to traverse sieve pores, facilitating its systemic spread along sieve tubes and inducing phloem necrosis. Within the xylem, Psa breaches pit membranes to migrate between adjacent vessels. Furthermore, phloem fibers act as an initial barrier at the early stages of infection, delaying Psa's entry into vascular tissues during its journey to the xylem. Additionally, at the junctions of stem–stem or stem-leaf, branch trace or leaf trace mediates the bacterial organ-to-organ translocation, thus facilitating the systemic progression of disease. In conclusion, our findings shed light on the cellular mechanism employed by Psa to exploit the woody plant's vascular network for infection, thereby enhancing a better understanding of the biology of this poorly defined bacterium. These insights carry implications for the pathogenesis of Psa and other vascular pathogens, offering theoretical guidance for effective control strategies.

中文翻译：

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血管网络介导的丁香假单胞菌全身传播。猕猴桃引起猕猴桃细菌性溃疡病


丁香假单胞菌 pv.猕猴桃 (Psa) 通过侵入多个植物器官的维管组织，引起破坏性的猕猴桃细菌性溃疡病。然而，其在这些特殊血管内的全身传播和细胞间运动的细胞机制仍不清楚。在这项研究中，使用 Psa-GFP 菌株和各种显微技术来研究猕猴桃和 Psa 之间的相互作用。我们的结果表明，Psa 战略性地利用宿主血管导管进行全身运动，其中木质部血管是主要途径。在韧皮部中，Psa 表现出细菌形状的适应性改变以穿过筛孔，促进其沿着筛管全身扩散并诱导韧皮部坏死。在木质部内，Psa 突破纹孔膜，在相邻导管之间迁移。此外，韧皮部纤维在感染的早期阶段充当初始屏障，延迟 Psa 在到达木质部的过程中进入维管组织。此外，在茎-茎或茎-叶的连接处，枝痕或叶痕介导细菌器官到器官的易位，从而促进疾病的全身进展。总之，我们的研究结果揭示了 Psa 利用木本植物的维管网络进行感染的细胞机制，从而增强了对这种定义不明确的细菌的生物学的更好理解。这些见解对 Psa 和其他血管病原体的发病机制具有重要意义，为有效的控制策略提供理论指导。