title: Comparative transcriptome analyses on silk glands of six silkmoths imply the genetic basis of silk structure and coloration.
abstract: 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.
authors.affiliation: Kunming University of Science and Technology, 727 South Jingming Road, Chenggong District, Kunming, Yunnan Province, 650500, China.|State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiaochang Road, Kunming, Yunnan Province, 650223, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Key Sericultural Laboratory of Agricultural Ministry, Institute of Sericulture and Systems Biology, Southwest University, 2 Tiansheng Road, Beibei District, Chongqing, 400715, China.
authors.forename: Fangyin
authors.initials: F
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiaochang Road, Kunming, Yunnan Province, 650223, China.
authors.forename: Yandong
authors.initials: Y
authors.lastname: Ren
authors.affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiaochang Road, Kunming, Yunnan Province, 650223, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiaochang Road, Kunming, Yunnan Province, 650223, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Institute of Zoology, Chinese Academy of Sciences, 69 East Beichen Road, Chaoyang District, Beijing, 100101, China.
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Yang
authors.affiliation: Shenyang Agricultural University, 120 Dongling Road, Shenhe District, Shenyang Province, 110866, China.
authors.forename: Yanqun
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Center for Epigenetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiaochang Road, Kunming, Yunnan Province, 650223, China. wwang@mail.kiz.ac.cn.
authors.forename: Wen
authors.initials: W
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiaochang Road, Kunming, Yunnan Province, 650223, China. xiangh@mail.kiz.ac.cn.
authors.forename: Hui
authors.initials: H
authors.lastname: Xiang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000235:genetics*; D019295:Computational Biology; D005349:Fibroins / Q000737:chemistry / Q000235:genetics; D056726:Genetic Association Studies; D014644:Genetic Variation; D059014:High-Throughput Nucleotide Sequencing; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D010802:Phylogeny; D019655:Quantitative Trait, Heritable; D047030:Sericins / Q000737:chemistry / Q000235:genetics; D047011:Silk; D059467:Transcriptome
chemical_list: D019476:Insect Proteins; D047030:Sericins; D047011:Silk; D005349:Fibroins