Antioxidant enzyme activities in different genders and tissues of amphioxus Branchiostoma belcheri tsingtauense

Information regarding antioxidant enzymes in amphioxus remains lacking, and this study was carried out to examine the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in different genders and tissues of amphioxus Branchiostoma belcheri tsingtauense. Results show that (1) CuZn-SOD, CAT and GPX activities in the whole amphioxus B. belcheri tsing- tauense were basically at the same levels in male and female amphioxus, whereas both T-SOD and Mn-SOD activities in male amphioxus were significantly higher than that in the female (P<0.05); (2) The testis had significantly higher T-SOD and CuZn-SOD activities than the ovary (P<0.05); (3) CuZn-SOD activity was undetectable in the guts of male and female amphioxus; (4) For both male and female am- phioxus, the activities of CAT and GPX in the gonads including testis and ovary were the lowest (P<0.05) among the tissues examined; (5) The gut and gill had the same level GPX activities while the gut had a higher CAT activity; (6) There was no clear difference in CAT and GPX activities in the corresponding tissues between male and female amphioxus. The study on SOD, CAT and GPX activities in different genders and tissues of the protochordate provides data for future comparison of amphioxus antioxidant enzymes with those of invertebrates and vertebrates.     

文昌鱼与比较基因组学和分子发育生物学

文昌鱼是现存的与脊椎动物原始祖先最接近的无脊椎动物，长期以来一直作为研究动物进化和胚胎发育的典型材料。目前，文昌鱼的基因序列和表达模式已经被广泛用于不同物种之间的比较基因组学研究和发育同源性分析中。文昌鱼独特的进化地位和它未经复制的基因组使其在比较基因组学中有着无可比拟的优越性，通过对文昌鱼、无脊椎动物和脊椎动物的基因组之间的比较，可以揭示脊椎动物原始祖先基因组的结构和演化过程进而探索人类的起源。同时，通过对文昌鱼和其它物种发育基因表达图式的比较可以显示不同生物身体部位之间的同源关系，并可以了解发育基因是如何引起不同物种之间形态变化的。     

Gel microbead cultivation with a subenrichment procedure can yield better bacterial cultivability from a seawater sample than standard plating method

A gel microbead (GMD) cultivation method was employed to cultivate microorganisms from an amphioxus breeding zone in Qingdao, P. R. China. The culture results were compared with those by standard plating method. In the GMD-based method, the microcolony-forming GMDs were sorted by fluorescence-activated cell sorting (FACS). To further get pure cultures, a subsequent enrichment culture and a streaking purification procedure were conducted on marine R2A medium. Eighty bacterial strains isolated by the GMD-based method were randomly selected for sequencing. These isolates belonged to Alphaproteobacteria (33%), Gammaproteobacteria (44%), Bacteroidetes (11%), Actinobacteria (5%), Firmicutes (5%), Epsilonproteobacteria (1%), and Verrucomicrobia (1%), the last two groups being usually difficult to culture. The 16S rRNA gene sequences revealed a diverse community with 91.1%-100% of the bacterial rRNAs similarities. Thirteen strains were sharing 16S rRNA gene sequence which was less than 97% similar to any other rRNA genes currently deposited in TYP16S database. Seventy isolates derived from the standard plating method fell into 4 different taxonomic groups: Alphaproteobacteria (9%), Gammaproteobacteria (81%), Bacteroidetes (7%) and Firmicutes (3%) with a 16S rRNA gene sequence similarities between 95.8%-100%, in which only 3 strains were sharing 16S rRNA gene sequence of less than 97%. The results indicated that the GMD-based method with subenrichment culture yielded more taxonomic groups and more novel microbial strains, including members of previously rarely cultured groups, when compared with the standard plating method, and that this method markedly improved the bacterial cultivability.     

Morphological and functional studies on the epidermal cells of amphioxus (Branchiostoma belcheri tsingtauense) at different developmental stages

Epidermal cells of amphioxus at different developmental stages were investigated by electron microscopy and colloidal carbon tracing experiments. Amphioxus epidermal cells showed different ultrastructural characteristics at larval and adult stages. The epidermal cells at all larval stages studied (24–96 h) had numerous vesicles containing electron dense materials in their apical cytoplasm. In tracing experiments, carbon particles were found in apical vesicles and interoellular spaces. Under scanning electron microscope, many crater-like protrusions were observed on the surface of the cells. These results indicated that amphioxus larval epidermal cells may be capable of endocytosis. The epidermal cells of 3-month and adult amphioxus were obviously secretory ones characterized by well-developed peripheral filaments, a prominent Golgi apparatus and abundant apical secretory vesicles. This study also showed that adult amphioxus body surface mucus contained lectin that could agglutinate human red blood cells. The authors propose that the epidermal cells of amphioxus larva and adult may contribute to the immune defense of the amimal by different means. Project 3860811 supported by NSFC and study also supported by the Shandong Natural Science Foundation (Grant No. 92D1144).