Diapause specific gene expression in the eggs of multivoltine silkworm Bombyx mori, identified by suppressive subtractive hybridization

Molecular mechanism controlling egg diapause remains obscure in silkworm, Bombyx mori. An attempt is made to decipher various molecular events occurring during embryonic diapause in multivoltine silkworm, B. mori. Using suppressive subtractive hybridization (SSH), 186 cDNA clones isolated from both diapause and nondiapause eggs were sequenced. Of the sequenced clones, 29 matched with silkbase entries and these identified putative genes were classified into six functional groups such as regulatory, food utilization, stress response, metabolic, ribosomal and transposable elements. Among these genes, twelve belonged to regulatory group while, one taste receptor type 2 member 117 gene was related to food utilization. One heat shock cognate 70 kDa protein and 3 of the ubiquitin family were identified under stress response category. Similarly, four genes were identified as metabolic genes, 3 belonging to chitin family and one propanediol utilization protein. Of the seven genes identified in ribosomal groups, most of them were 60s ribosomal protein subunits. However, one negative regulation of transcription gene identified was a transposable element. The qPCR analysis confirmed the expression of 21 of the above genes, wherein, 6 were upregulated during diapause, 12 during non-diapause, while, 3 remained unchanged.