Chitin deacetylases (CDAs, including CDA1 and CDA2) are considered key enzymes for body cuticle formation and tracheal morphogenesis in various insect species. However, their functions in the formation of the cuticular intima of the foregut and hindgut are unclear. Here, we investigated the roles of their respective genes LmCDA1 and LmCDA2 in this process, in the hemimetabolous insect Locusta migratoria. Transcripts of LmCDA1 and LmCDA2 were highly expressed both before and after molting in the foregut. In the hindgut, their expression was high only before molting. In both the foregut and hindgut, LmCDA1 protein was localized in the basal half of the chitin matrix (procuticle), whereas LmCDA2 was detected in the upper half of the procuticle. Knockdown of LmCDA1 by RNA interference (RNAi) in 5th-instar nymphs caused no visible defects of the hindgut cuticle. By contrast, the chitinous lamellae of the cuticular intima in the foregut of knockdown animals were less compact than in control animals. RNAi against LmCDA2 led to thickening of both the foregut and hindgut cuticles, with a greater number of thinner laminae than in the respective control cuticles. Taken together, our results show that LmCDA1 and LmCDA2 have distinct, but overlapping, functions in chitin organization in the foregut cuticle. However, in the hindgut, this process seems independent of LmCDA1 activity but requires LmCDA2 function. Thus, the CDAs reflect tissue-specific differences in cuticular organization and function, which need further detailed molecular and histological analyses for full comprehension.

中文翻译：

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LmCDA1和LmCDA2在蝗虫前肠和后肠表皮形成中的作用

几丁质脱乙酰酶（CDA，包括 CDA1 和 CDA2）被认为是各种昆虫物种体表皮形成和气管形态发生的关键酶。然而，它们在前肠和后肠表皮内膜形成中的功能尚不清楚。在这里，我们研究了它们各自的基因LmCDA1和LmCDA2在这个过程中的作用，在半代谢昆虫Locusta migratoria 中。LmCDA1和LmCDA2 的转录本在前肠蜕皮前后均高度表达。在后肠中，它们只有在蜕皮前才会有高表达。在前肠和后肠中，LmCDA1 蛋白定位于几丁质基质（前皮）的基底半部，而 LmCDA2 位于前皮的上半部。通过 RNA 干扰 (RNAi) 在 5 龄若虫中敲除 LmCDA1不会导致后肠表皮出现明显缺陷。相比之下，敲除动物前肠内膜的几丁质薄片不如对照动物紧密。针对LmCDA2 的RNAi导致前肠和后肠表皮增厚，与相应的对照表皮相比，薄层的数量更多。总之，我们的结果表明 LmCDA1 和 LmCDA2 在前肠角质层的几丁质组织中具有不同但重叠的功能。然而，在后肠中，这个过程似乎与 LmCDA1 活动无关，但需要 LmCDA2 功能。因此，CDA 反映了表皮组织和功能的组织特异性差异，需要进一步详细的分子和组织学分析才能充分理解。