细胞自噬介导番茄环纹斑点病毒突破西花蓟马唾液腺释放屏障的传毒机理

Overcoming salivary gland escape barriers serves as a crucial determinant of virus transmission by insects. It is not yet known how Tomato zonate spot virus overcomes salivary gland escape barriers of Frankliniella occidentalis for the transmission. Previous studies demonstrated that virus-containing autophagosome-like vesicles were distributed within or out of the salivary cavity of viruliferous F. occidentalis. Inhibition of autophagy considerably decreased the virus transmission rates by its vectors. We further found that disrupting of salivary gland myosin significantly decreased the virus transmission rates by viruliferous F. occidentalis but its autophagy remained unaffected, suggesting TZSV probably induce autophagosome vesicles to overcome salivary gland escape barriers and derived by the myosin for transmission. The proposed project will study autophagosomes induced by TZSV that is the primary way for virus overcoming salivary gland escape barriers, and the role of myosin in the process of translocation apical plasmalemma with virus-containing autophagosomes. The results will provide a comprehensive insight to combat barriers responsible for transmission of vector-transmitted viruses and facilitate to find a new strategy for blocking the horizontal transmission of viruses.

虫媒病毒通过介体唾液腺细胞质膜的能力决定了介体昆虫的传毒效率。西花蓟马是番茄环纹斑点病毒（TZSV）重要媒介，但目前还不明确TZSV如何克服西花蓟马唾液腺释放屏障实现传毒。前期研究发现，携带TZSV的西花蓟马唾液腔的质膜内外均存在包裹病毒粒子的类自噬泡结构，抑制自噬泡形成能显著降低蓟马传毒率；肌球蛋白（myosin）抑制剂处理带毒蓟马，蓟马传毒率显著下降，但对细胞自噬形成无影响。因此，TZSV能否借助细胞自噬泡，在myosin推动下穿过唾液腺细胞质膜释放到唾液腔实现传毒是个重要科学问题。本项目拟研究TZSV侵染激活西花蓟马唾液腺细胞自噬反应、自噬泡是TZSV突破介体蓟马唾液腺质膜的关键途径，及myosin在带毒自噬泡穿膜过程中的作用，阐明myosin协助TZSV诱导形成包裹病毒的自噬泡穿过质膜进入到唾液腔，完成病毒释放的机理。研究结果将为探索阻断病毒水平传播的策略构建提供理论依据和指导。

由番茄环纹斑点病毒（Tomato zonate spot virus, TZSV）引起的番茄环纹斑点病毒病主要由西花蓟马（Franiklinella occidentalis）等蓟马类昆虫以持久增殖型方式传播。该病害是我国西南地区重要的虫传病毒病害，并有蔓延暴发的趋势。持久增殖型病毒经中肠扩散侵入昆虫唾液腺细胞后，会进行复制增殖，进而随着分泌的唾液进入唾液腺腺泡细胞的内腔中，然后在昆虫取食时随唾液传至寄主植物。本研究发现，西花蓟马在感病植株上取食1小时后病毒即可在肠腔建立初侵染点，4小时后病毒即可侵染西花蓟马唾液腺；病毒侵染西花蓟马消化道可激活细胞自噬反应，包裹病毒的自噬泡穿过上皮细胞进入肌肉组织，再穿过肌肉组织释放到血腔。同时，自噬泡还可携带病毒从唾液腺泡细胞释放到唾液腔，完成病毒由中肠上皮细胞到唾液腔的扩散过程。在此过程中，细胞骨架蛋白myosin可为自噬泡携带病毒运动提供轨道和动力。此外，本研究还发现TZSV侵染辣椒植株显著降低辣椒叶片水杨酸(SA)的含量，进而提高介体西花蓟马种群适合度；同时，TZSV侵染的辣椒植株进一步提高了西花蓟马在与棕榈蓟马种间竞争中的优势，促进西花蓟马对TZSV的传播。研究结果为探索病害的流行规律和制定有效的防控策略提供理论支撑。