比对6种转录组 中国学者发现遗传奥秘

　　

　蚕丝业是我国重要的特色产业，但蚕丝业主体——家蚕丝，与自然界野生的鳞翅目绢丝昆虫尤其是大蚕蛾科昆虫的茧丝相比，在一些特性如颜色和抗皱等方面不及野蚕茧丝。

　　中国科学院昆明动物研究所基因起源课题组与昆明理工大学教授董扬、西南大学教授代方银等研究组合作，开展了野生绢丝昆虫遗传资源挖掘工作。

   通过比较6种重要绢丝昆虫的丝腺转录组，鉴定到一批与丝腺发育相关的大蚕蛾科特有基因。茧丝结构蛋白分析显示，丝素重链蛋白的理化特性如等电点、亲水曲线等在大蚕蛾科内部不同属种之间存在差异；有趣的是，尽管大蚕蛾科野蚕蛾的丝蛋白都缺乏其他鳞翅目绢丝昆虫普遍存在的丝素轻链蛋白，但是轻、重链连接子P25蛋白仅在大蚕蛾科部分属种中丢失；丝胶蛋白在大蚕蛾科与蚕蛾科之间及大蚕蛾科内部存在丰富的丢失/扩增现象，这也导致了大蚕蛾科丝胶蛋白显著的种属异质性。研究还鉴定到一批与大蚕蛾科稳定茧色性状相关的基因，主要富集在转移酶类。

　　该研究分析了大蚕蛾科独特的茧丝性状相关基因资源，提示茧丝的物理特性可能由丝蛋白特性、丝腺微环境等众多因素决定，尤其是茧色稳定性可能归因于色素分子的酶促反应。

　　该研究为大蚕蛾科茧丝进化机制提供了初步线索，为未来家蚕丝的遗传改造提供了潜在的候选基因资源。

　　该研究结果近期发表在BMC genomics 上，基因起源课题组的副研究员相辉和研究员王文为共同通讯作者。

　　该研究由“973”项目、“西部之光”重点项目资助。

原文摘要：

Comparative transcriptome analyses on silk glands of six silkmoths imply the genetic basis of silk structure and coloration

Background

Silk has numerous unique properties that make it a staple of textile manufacturing for several thousand years. However, wider applications of silk in modern have been stalled due to limitations of traditional silk produced by Bombyx mori. While silk is commonly produced by B. mori, several wild non-mulberry silkmoths--especially members of family Saturniidae--produce silk with superior properties that may be useful for wider applications. Further utilization of such silks is hampered by the non-domestication status or limited culturing population of wild silkworms. To date there is insufficient basic genomic or transcriptomic data on these organisms or their silk production.

Results

We sequenced and compared the transcriptomes of silk glands of six Saturniidae wild silkmoth species through next-generation sequencing technology, identifying 37758 ~ 51734 silkmoth unigenes, at least 36.3% of which are annotated with an e-value less than 10−5. Sequence analyses of these unigenes identified a batch of genes specific to Saturniidae that are enriched in growth and development. Analyses of silk proteins including fibroin and sericin indicate intra-genus conservation and inter-genus diversification of silk protein features among the wild silkmoths, e.g., isoelectric points, hydrophilicity profile and amino acid composition in motifs of silk H-fibroin. Interestingly, we identified p25 in two of the silkmoths, which were previously predicted to be absent in Saturniidae. There are rapid evolutionary changes in sericin proteins, which might account for the highly heterogeneity of sericin in Saturniidae silkmoths. Within the six sikmoths, both colored-cocoon silkmoth specific transcripts and differentially expressed genes between the colored-cocoon and non-colored-cocoon silkmoths are significantly enriched in catalytic activity, especially transferase activity, suggesting potentially viable targets for future gene mining or genetic manipulation.

Conclusions

Our results characterize novel and potentially valuable gene resources of saturniid silkmoths that may facilitate future genetic improvement and modification of mulberry silkworms. Our results suggest that the disparate features of silk--coloration, retention, strength, etc. --are likely not only due to silk proteins, but also to the environment of silk assembly, and more specifically, that stable silk coloration exhibited by some Saturniidae silkmoths may be attributable to active catalytic progress in pigmentation.