Kimura Satoshi, Nakayama Kei, Wada Masahisa, Kim Ung-Jin, Azumi Kaoru, Ojima Takao, Nozawa Akino, Kitamura Shin-Ichi, Hirose Euichi
Department of Biomaterial Science, Graduate School of Agricultural and Life Science, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Dis Aquat Organ. 2015 Oct 16;116(2):143-8. doi: 10.3354/dao02913.
Soft tunic syndrome is a fatal disease in the edible ascidian Halocynthia roretzi, causing serious damage to ascidian aquaculture in Korea and Japan. In diseased individuals, the tunic, an integumentary extracellular matrix of ascidians, softens and eventually tears. This is an infectious disease caused by the kinetoplastid flagellate Azumiobodo hoyamushi. However, the mechanism of tunic softening remains unknown. Because cellulose fibrils are the main component of the tunic, we compared the contents and structures of cellulose in healthy and diseased tunics by means of biochemical quantification and X-ray diffractometry. Unexpectedly, the cellulose contents and structures of cellulose microfibrils were almost the same regardless of the presence or absence of the disease. Therefore, it is unlikely that thinning of the microfibrils occurred in the softened tunic, because digestion should have resulted in decreases in crystallinity index and crystallite size. Moreover, cellulase was not detected in pure cultures of A. hoyamushi in biochemical and expressed sequence tag analyses. These results indicate that cellulose degradation does not occur in the softened tunic.
软被囊综合征是可食用海鞘柄海鞘的一种致命疾病，对韩国和日本的海鞘养殖业造成严重破坏。在患病个体中，海鞘的被囊（一种海鞘的体表细胞外基质）会软化并最终撕裂。这是一种由动质体鞭毛虫阿苏拟波豆虫引起的传染病。然而，被囊软化的机制仍然未知。由于纤维素原纤维是被囊的主要成分，我们通过生化定量和X射线衍射法比较了健康和患病被囊中纤维素的含量和结构。出乎意料的是，无论疾病是否存在，纤维素微原纤维的纤维素含量和结构几乎相同。因此，微原纤维在软化的被囊中不太可能发生变细，因为消化应该会导致结晶度指数和微晶尺寸降低。此外，在阿苏拟波豆虫的纯培养物中，通过生化和表达序列标签分析未检测到纤维素酶。这些结果表明，软化的被囊中不会发生纤维素降解。
