NUCLEOTIDE SEQUENCE ANALYSIS OF LIGHT CHAIN FIBROIN GENE OF SEVERAL VIETNAMESE BIVOLTINE SILKWORM STRAIN AND THEIR TETRA-PARENTAL HYBRIDS

Abstract

Fibroin of the silkwonn Bambyx mori L. cansits a heavy chain FH fibroin of about 350 kDa and a light chain FL fibroin gene of about 25 kDa, linked by a disulfide bond. The H-L linkage is essential for the secretion of a vast amount of fibroin. Total genomic DNA was extracted from sixteen individual tissue samples of four Vietnamese bivoltine silkworm strains and their double cross hybrids. A primer set (FLI and FL2) designed by Yasucochi (1999) was applied to amplify a portion of the FL gene. The DNA fragment of 752 bp was obtained from genomic DNA and inserted into pCR® 2.1 TOPO vector for sequencing. The results showed that the sizes of amplified gene fragments range from 733bp to 735bp. Their sequence similarities compared to those in GenBank vary from 93,94 to 99,65%. We also confirmed that the FL gene sequences of sixteen samples were mutated at many positions compared with the sequence of AF541967 deposited in GenBank. There is correlationship between above-mentioned variations and cocoon's shapes, Vietnamese bivoltine silkworm strains well as genetic traits of pure strains and their tetra-parental hybrids. This genetic marker may be used in breeding and selection of silkworm. These sequences have been registered in GenBank.