Transcriptomic analysis reveals the regulation network of BmKruppel homolog 1 in the oocyte development of Bombyx mori

Kriippel homolog 1(Kr-hl),a zinc finger transcription factor,is involved in the metamorphosis and adult reproduction of insects.However,the role of Kr-hl in reproduction of holometabolic insects remains to be elucidated.The regulation network of 7-associated genes in the reproduction in Bombyx mori was investigated in this study.The higher expression level of BmKr-hl in the ovaries was detected during the late pupal stage and adults.RNA interference(RNAi)-mediated depletion of BmKr-hl in the female at day 6 of pupae resulted in abnormal oocytes at 48 h post-double-stranded RNA treatment,which showed less yolk protein deposition and partially transparent chorion.RNA-seq and subsequent differentially expressed transcripts analysis showed that knockdown of BmKr-hl caused a decrease in the expression of 2882 genes and an increase in the expression of 2565 genes in the oocytes at day 8 of pupae.Totally,27 genes coding for transcription factors were down-regulated,while six genes coding for other transcription factors were up-regulated.BmKr-hl bound to the Kr-hl binding site of the transcription factors AP-1(activating protein-1)and FOXG1 to increase their messenger RNA tran・scripts in the BmN cells,respectively.Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses of that positively co-expressed with AP-1 and FOXG1 transcripts showed mainly enrichment in the metabolic-related pathways,the nu・tri ent absorption and the yolk protein absorption processes.These data suggested that BmKr-h 1 might directly regulate the metabolic-related pathways,the nutrient absorption and the yolk protein absorption processes or probably through AP-1 and/or FOXG1 to regulate oocyte development.

Genome-wide microarray screening for Bombyx mori genes related to transmitting the determination outcome of whether to produce diapause or nondiapause eggs

The bivoltine silkworm Bombyx mori （Lepidoptera： Bombycidae） exhibits a maternally controlled embryonic diapause. Maternal silkworms decide whether to lay diapause or nondiapause eggs depending on environmental factors such as the temperature and photoperiod during the egg and larval stages, and then induce diapause eggs during the pupal stage. However, little is known about the molecular mechanism that conveys the outcome of whether to produce diapause or nondiapause eggs from the egg or larval stages to the pupal stage. This study used microarray analysis to investigate differentially expressed genes in the larval brains of diapause- and nondiapause-egg producers, to which bivoltine silkworms were destined by thermal or photic stimulation during the egg stage. The cytochrome P450 18al and Kriippel homolog i genes were upregulated in producers of diapause eggs compared with those of nondiapause eggs under both experimental conditions. Cytochrome P450 18al encodes a key enzyme for steroid hormone inactivation and Krfippel homolog 1 is an early juvenile hormone-inducible gene that mediates the repression of metamorphosis. The upregulation of these genes during the larval stage might be involved in the signaling pathway that transmits information about the diapause program from the egg stage to the pupal stage in the silkworm.