Chitin, the major structural polysaccharide of arthropods, is an important constituent of the insect extracellular structures, cuticle and gut peritrophic matrix. Synthesis of cuticular chitin is strictly coordinated with the ecdysone-regulated molting cycle of insect development (the term "ecdysone" is used in this paper instead of "ecdysteroids" since the exact ratio of various hormonal forms changes during metamorphosis). Based on observed similarities between the fungal chitin synthases and other processive beta-glycosyltransferases, we have identified the first insect chitin synthase genes, DmeChSA and DmeChSB (Database accession numbers: EMBL/GenBank/DDBJ A83122, A83126, AJ309488, AJ309489), from Drosophila melanogaster. Chromosomal localization has identified these genes close to and on either side of the centromere of the third chromosome. Partial cDNA clones of both genes have been isolated from a pupal cDNA library. To obtain the first insight into the transcriptional regulation of chitin synthesis, we have monitored the expression of DmeChSA and DmeChSB during the periods of the late-larval and prepupal ecdysone pulses that direct metamorphosis. Transcripts of either gene are barely detected prior to and during the late-larval ecdysone pulse. Once the late-larval ecdysone pulse is ceased completely, both DmeChSA and DmeChSB genes show a remarkable up-regulation.

中文翻译：

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果蝇变态发生期间几丁质合酶DmeChSA和DmeChSB基因的阶段特异性表达。

甲壳素是节肢动物的主要结构多糖，是昆虫细胞外结构，角质层和肠道周围营养基质的重要组成部分。表皮甲壳质的合成与蜕皮激素调节的昆虫蜕皮周期严格协调（本文使用术语“蜕皮激素”代替“蜕皮甾类”，因为在变态过程中各种激素形式的确切比例会发生变化）。基于观察到的真菌几丁质合酶与其他进行性β-糖基转移酶之间的相似性，我们从果蝇中鉴定了第一个昆虫几丁质合酶基因DmeChSA和DmeChSB（数据库登录号：EMBL / GenBank / DDBJ A83122，A83126，AJ309488，AJ309489）黑色素瘤。染色体定位已鉴定出这些基因靠近第三条染色体着丝粒并在其两侧。从genescDNA文库中分离了两个基因的部分cDNA克隆。为了获得对几丁质合成的转录调控的第一见解，我们已经监测了指导变态的后期幼虫和pu前蜕皮激素脉冲期间DmeChSA和DmeChSB的表达。在幼虫蜕皮激素脉冲之前和期间几乎未检测到任何一个基因的转录本。一旦幼虫蜕皮激素脉冲完全停止，DmeChSA和DmeChSB基因均显示出明显的上调。我们已经监测了DmeChSA和DmeChSB在幼虫晚期和pu前蜕皮激素脉冲期间的表达，这些脉冲指导了变态。在幼虫蜕皮激素脉冲之前和期间几乎未检测到任何一个基因的转录本。一旦幼虫蜕皮激素脉冲完全停止，DmeChSA和DmeChSB基因均显示出明显的上调。我们已经监测了DmeChSA和DmeChSB在幼虫晚期和pu前蜕皮激素脉冲期间的表达，这些脉冲指导了变态。在幼虫蜕皮激素脉冲之前和期间几乎未检测到任何一个基因的转录本。一旦幼虫蜕皮激素脉冲完全停止，DmeChSA和DmeChSB基因均显示出明显的上调。