Structure of the gene for the arylphorin-type storage protein SP 2 of Bombyx mori.
Two forms of storage proteins termed "SP 1" and "SP 2", respectively, accumulate in a stage-dependent fashion in the larval hemolymph of the silkworm Bombyx mori. We have cloned and analyzed the genomic sequence encoding SP 2, an arylphorin-type storage protein. The SP 2 structural gene contains five exons spanning over 5 kilobases of chromosomal DNA. The transcription initiation site of the SP 2 gene was identified at the nucleotide level and a typical TATA box was located 30 base pairs upstream of the transcription initiation site. The 5'-flanking region of the gene contains a sequence homologous to the SV 40 enhancer "core" structure. A region homologous to the Drosophila enhancer sequence predicted for the fat body specificity of gene expression exists in the 5'-upstream region. Developmental profiles of the SP 2 mRNA and its precursor in the fat body indicate that the biosynthesis of SP 2 is developmentally regulated at the level of transcription. The exon/intron composition of the SP 2 gene is remarkably similar to that of the SP 1 gene. Moreover, the deduced primary structures of SP 1 and SP 2 exhibit nearly 30% homology, implying that two storage protein genes of the B. mori silkworm might have evolved from a common ancestor.
Fujii
T
T
Department of Biology, Tokyo Metropolitan University, Japan.
Sakurai
H
H
Izumi
S
S
Tomino
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics* / Q000254:growth & development; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D004330:Drosophila / Q000235:genetics; D004742:Enhancer Elements, Genetic; D005091:Exons; D005216:Fat Body / Q000378:metabolism; D005796:Genes; D007301:Insect Hormones / Q000235:genetics*; D019476:Insect Proteins; D007438:Introns; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D013539:Simian virus 40 / Q000235:genetics; D014158:Transcription, Genetic
D007301:Insect Hormones; D019476:Insect Proteins; D012333:RNA, Messenger; C041137:storage proteins, Insecta; D004247:DNA