Cloning of silkworm 3-hydroxyisobutyrate dehydrogenase gene and its expression patterns analysis in simulated weightless environment

The full length cDNA of silkworm hibadh gene was cloned by RT-PCR and RACE (Rapid amplification of cDNA ends) technique. The hibadh gene and its deduced amino acid sequences were analyzed. The tissue distribution of hibadh gene in 5th instar silkworm larvae was tested by RT-PCR. The expression patterns of hibadh gene in simulated weightless environment were analyzed by real time RT-PCR. The results showed that the full length hibadh cDNA sequence was 1074 bp in lenth, including an open read frame of 969 bp encoding the entire coding region of Hibadh (GenBank accession No. EU719652). The deduced amino acid sequence similarities of hibadh between silkworm and Burkholderia ambifaria, Drosophila melanogaster, Apis mellifera, Xenopus tropicalis, Mus musculus, Homo sapiens were 46%, 43%, 48%, 44%, 45%, 45%, respectively. Signal peptide analysis showed that Hibadh was a secretory protein. There wasn't glycosyl-phosphatidyl inositol anchor site in Hibadh amino acid sequence. Molecular weight and isoelectric point of Hibadh were 34.1 kD and 9.14 respectively. The RT-PCR tests indicated that the hibadh gene expressed in head, silk gland, midgut, cuticle, blood, fat body, tuba malpighii of the 5th instar silkworm larvae. There were different expression patterns of hibadh gene during different silkworm embryo period in simulated weightless environment. Simulated weightlessness resulted in the expression of silkworm hibadh gene up regulated 2.3-fold (P < 0.05), up regulated 4.6-fold (P < 0.01), down regulated 7.6-fold (P < 0.01), down regulated 2.6-fold (P < 0.05) during apophysis formation period, inverse period, trachea formation period, and whole embryo period, respectively. There was no significant change of hibadh gene expression during other period of silkworm embryo between simulated weightless and control groups. There were different response patterns to simulated weightless environment between hibadh gene and whole body of silkworm. Gene showed much higher sensitivity compared to whole body in response to environment. This study is useful for the further research on the gravity biological mechanism of hibadh gene.