Diapause-specific gene expression in pupae of the flesh fly Sarcophaga crassipalpis

Several cDNAs isolated from brains of diapausing pupae of the flesh fly, Sarcophaga crassipalpis, show expression patterns unique to diapause. To isolate such cDNAs a diapause pupal brain cDNA library was screened by using an elimination hybridization technique, and cDNAs that did not hybridize with cDNA probes constructed from the RNA of nondiapausing pupae were selected for further screening. The 95 clones that did not hybridize in the initial library screen were selected for further characterization. These clones were then screened against diapause and nondiapause pupal poly(A)(+) Northern blots. The secondary screen identified 4 diapause-up-regulated clones, 7 diapause-down-regulated clones, 8 clones expressed equally in both diapause and nondiapause, and 75 clones without detectable expression. The diapause-up-regulated and down-regulated clones were further characterized by partial DNA sequencing and identity searches by using GenBank. Identities between our cloned cDNAs and other genes included those linked to cell cycle progression, stress responses, and DNA repair processes. The results suggest that insect diapause is not merely a shutdown of gene expression but is a unique, developmental pathway characterized by the expression of a novel set of genes.

从肉蝇（Sarcophaga crassipalpis）滞育蛹脑组织中分离得到的若干互补DNA（complementary DNA，cDNA），呈现出仅在滞育状态下特有的表达模式。为分离此类cDNA，研究人员采用扣除杂交技术对滞育蛹脑组织cDNA文库进行筛选，选取未与非滞育蛹RNA构建的cDNA探针发生杂交的序列，用于后续筛选。初筛中未发生杂交的95个克隆被选出，用于进一步的特征分析。随后，针对滞育与非滞育蛹的聚腺苷酸化RNA（poly(A)(+)）Northern印迹（Northern blots），对这些克隆开展二次筛选。二次筛选结果显示，共获得4个滞育上调克隆、7个滞育下调克隆、8个在滞育与非滞育状态下表达水平无差异的克隆，以及75个未检测到表达的克隆。研究人员通过部分DNA测序及基于基因银行（GenBank）的同源性检索，对滞育上调与下调克隆开展进一步特征分析。本研究克隆的cDNA与其他基因的同源序列，涉及细胞周期进程、应激反应及DNA修复过程相关基因。研究结果表明，昆虫滞育并非仅仅是基因表达的静默关闭，而是一条以全新基因集表达为特征的独特发育通路。