Abstract：
Soft tunic syndrome is an infectious disease caused by the flagellate Azumiobodo hoyamushi, which severely damages the aquaculture of the edible ascidian Halocynthia roretzi. Tunic is a cellulosic extracellular matrix entirely covering the body in ascidians and other tunicates, and its dense cuticle layer covers the tunic surface as a physical barrier against microorganisms. When the tunic of intact H. roretzi individuals was cut into strips, electron-dense fibers (DFs) appeared on the cut surface of the tunic matrix and aggregated to regenerate a new cuticular layer in seawater within a few days. DF formation was partially or completely inhibited in individuals with soft tunic syndrome, and DF formation was also inhibited by the presence of some proteases, indicating the involvement of proteolysis in the process of tunic softening as well as cuticle regeneration. Using pure cultures of the causative flagellate A. hoyamushi, the expression of protease genes and secretion of some proteases were confirmed by RNA-seq analysis and a 4-methylcoumaryl-7-amide substrate assay. Some of these proteases may degrade proteins in the tunic matrix. These findings suggest that the proteases of A. hoyamushi is the key to understanding the mechanisms of cuticular regeneration inhibition and tunic softening.
摘要：
软衣综合征是一种由鞭毛虫Azumiobodohoyamushi引起的传染病，这严重损害了可食用海鞘Halocynthiaroretzi的水产养殖。外衣是一种纤维素细胞外基质，完全覆盖海鞘和其他外衣，其致密的角质层覆盖了外衣表面，作为抵抗微生物的物理屏障。当完整的H.roretzi个体的外衣被切成条状时，电子致密纤维（DF）出现在外衣基质的切割表面，并在几天内在海水中聚集以再生新的角质层。在软膜综合征患者中，DF的形成被部分或完全抑制，和DF的形成也被一些蛋白酶的存在抑制，表明蛋白水解参与了外皮软化和角质层再生的过程。使用致病性鞭毛虫A.hoyamushi的纯培养物，通过RNA-seq分析和4-甲基香豆酰-7-酰胺底物测定证实了蛋白酶基因的表达和一些蛋白酶的分泌。这些蛋白酶中的一些可以降解外衣基质中的蛋白质。这些发现表明，A.hoyamushi的蛋白酶是理解表皮再生抑制和外衣软化机制的关键。
