Cellulose is not degraded in the tunic of the edible ascidian Halocynthia roretzi contracting soft tunic syndrome

Diseases of Aquatic Organisms

Satoshi Kimura¹  Akino Nozawa¹  Kaoru Azumi¹  Kei Nakayama¹  Masahisa Wada¹  Takao Ojima¹  Shin-Ichi Kitamura¹  Ung-Jin Kim¹  , Euichi Hirose¹ 

关键词: Cellulose content;    Cellulase;    X-ray diffractometry;    EST analysis;    Azumiobodo hoyamushi;    Ascidian aquaculture;   

DOI  :  10.3354/dao02913

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: 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.

【 授权许可】

Unknown