Analysis of ESTs and gene expression patterns of the poste-rior silkgland in the fifth instar larvae of silkworm, Bom-byx mori L.

Abstract

The fibroin gene expression pattern and regulation of the posterior silkgland were studied by means of expressed sequence tags (ESTs) using the first and fifth day larvae of the fifth instar of silkworm, Bombyx mori L (strain: C 108). The results showed that there were 911 repetitive ESTs and 1950 single sequences (Singlets) among total 2861 consentient sequences, which were spliced. 1335 sequences were identified and the other 1526 were unknown. 5560 sequences (55.89%) in the posterior silkgland cell of the silkworm were new ESTs without homology with EST data published by Mita et al. The number of repetitive ESTs and single sequences from the first day larvae of the fifth instar was double more than that of the fifth day of the same instar in the silkworms. The unigenes which were more than 50 in repetitive EST size (contig size) came to only about 0.5% in total consentient sequences. There were significant differences between gene expression frequencies, and expressed genes were related to fibroin synthesis and its secretion and fibroin composition. Comparing the fifth day with the first day of the fifth instar, the genes-expressed quantity of fibroin heavy-chain gene was 18 fold higher, fibroin light-chain gene 9 fold and fibroin P52 gene 8 fold. 508 genes functioned for cellular component and 315 for enzyme after function tracing. These results implied that the gene expression of the first day was mainly for preparation for fibroin synthesis except for the growth of silkgland cells, and the gene expression of the fifth day of the fifth instar was mainly for synthesizing and excreting fibroin. Because the ratio of heavy chain, light chain and p25 of fibroin was not 6:6:1 as theoretically expected, or its special H-chain structure, the H-chain gene was not easy to detect through EST technique. Most of genes among total 2861 consentient sequences functioned for fibroin synthesis and secretion. This suggested the fibroin synthesis and secretion procedure of the posterior silkgland was more complex than the knowledge we have.

Inhibition of silkworm vacuolar‐type ATPase activity by its inhibitor Bafilomycin A1 induces caspase‐dependent apoptosis in an embryonic cell line of silkworm

“…The posterior silk gland synthesizes liquid silk fibroin, the middle silk gland synthesizes sericin. Glued by sericin in the middle silk gland, liquid silk fibroin flows to the anterior silk gland to form gel‐like silk proteins under the interaction of biochemical factors (such as H + and metal ions) and physical forces, and then finally spun as solid silk fibers by the spinneret (Terry, Knight, Porter, & Vollrath, ; X. Wang et al, ; Zhong et al, ). The anterior silk gland is the key site for the conformational changes in silk fibroin.…”

Comparative analysis of the silk gland transcriptomes between the domestic and wild silkworms

“…To understand the tissue specificity and functional diversification, the silk gland transcriptome in domestic silkworm has been investigated in previous studies [ 10 - 13 ]. Expressed sequence tags were sequenced in the PSGs on days 1 and 5 of fifth-instar larvae [ 10 ]. Differential gene expression patterns between anterior/median silk glands (A/MSG) and PSGs were examined on day 3 of fifth-instar larvae [ 11 ].…”

Gene expression profiling in porcine mammary gland during lactation and identification of breed-and developmental-stage-specific genes

“…Single-pass, partial sequencing of randomly selected cDNA clones from cDNA libraries to generate expressed sequence tags (EST), combined with bioinformatics analysis, has proved powerful for the discovery of alternative splicing (AS) [3,4] , novel genes [5] and the characterization of gene function [6,7] , the differential and quantitative analysis of expression patterns [8,9] , as well as the evaluation of the gene expression profile in a given tissue [10][11][12] . Previous efforts to generate ESTs from mammary gland cDNA libraries were limited.…”