| Dpp gene play a pivotal roles in the embryonic development of insects. Its function has been researched much clear in Drosophila since its first reported in Drosophila melanogaster. During the early embryonic development of Drosophila, Dpp is responsible for dorsal/ventral polarity. Late, it functions in the definition of boundaries between segmental compartments. Also, Dpp along with wingless and hedgehog, defines the position of future appendage, including wings, legs and antenna. Besides, Dpp has a function in eye development. It encodes a morphogen which responsible for the progression of the morphogenetic furrow, the induction site of the Drosophila retina.Dpp is one of the fateful genes in the process of insect development and it is conserved widely in many species. Since its first report in Drosophila melanogaster, Dpp homologues have been identified in many other insects, nemotode (C.elegans), frog (Xenopus laevis), primary eukaryotic organism, plants and mammalian. We found a dpp homolog in the analysis of silkworm genome data. Silkworm( bombyx mori) is the representative of lepidoptera and study on its developmental mechanism is of great importance. In order to work out the regulatory mechanism of silkworm embryonic development, we performed a primary study on the homologous gene of dpp in silkworm, Bombyx mori.The main research contents and results are as follows:(1) The cloning of silkworm dpp homologous gene, Bmdpp. The cloned mRNA length of the Bmdpp gene is 1437bp, comprised an open reading frame of 1146 bp which coding for a protein of 381 amino acids, the molecular weight of the BmDpp protein is 38.6kD, pI is 9.18, and TGFb_propeptide and TGFβdomain exists in it. Amino acid sequence alignment shown BmDpp share 45% identity with the Dpp of Drosophila melanogaster, nucleotide sequence alignment between the cDNA and the genome sequence shown that, It has avlternative splicing on the 5',and both of them contains 2 extrons and 1 introns, and all the extron/intron splicing boundary obey the GT-AG rule.(2) In ordor to investigate the expression profile of Bmdpp gene in different tissues and different period during embryo development, RT-PCR was performed using the cDNA from fat body, silk gland, midgut, skin, head and gonad of Bombyx mori and egg of different period from before fertilization to 8d after egg laied during embryo development as template. The RT-PCR results shows that Bmdpp is expressed in all the tissues tested and it has a high expression in most period during embryonic development,but low expression or missing in 6h -14h after egg laying. This expression pattern is similar to that of Drosophila dpp homolog. We deduced that the Bmdpp play a similar roles with Drosophila dpp homolog during embryonic development of silkworm, Bombyx mori..(3) In order to express BmDpp protein in E.coli, the complete coding sequence of Bmdpp gene was subcloned into the pET-28a(+) expression vector and the recombinant plasmid was transformed into BL21 competent cell. Then single clone was picked up and incubated at 24℃with constant shake, add IPTG to the final concentration of 1mM when the OD value reached 0.6, and continue incubate at 37℃for 4 hours, the bacteria transformed with pET-28a(+) and bacteria without IPTG inducing were used as control. After SDS-PAGE electrophoresis, a protein band about 40 kD, the same as the predicted, was obvious compared with the control, indicating the Bmdpp gene was expressed in the E.coli.
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