The tracheal apical extracellular matrix (aECM) is vital for expansion of the tracheal lumen and supports the normal structure of the lumen to guarantee air entry and circulation in insects. Although it has been found that some cuticular proteins are involved in the organization of the aECM, unidentified factors still exist. Here, we found that mind the gap (Mtg), a predicted chitin‐binding protein, is required for the normal formation of the apical chitin matrix of airway tubes in the model holometabolous insect Drosophila melanogaster. Similar to chitin, the Mtg protein was linearly arranged in the tracheal dorsal trunk of the tracheae in Drosophila. Decreased mtg expression in the tracheae seriously affected the viability of larvae and caused tracheal chitin spiral defects in some larvae. Analysis of mtg mutant showed that mtg was required for normal development of tracheae in embryos. Irregular taenidial folds of some mtg mutant embryos were found on either lateral view of tracheal dorsal trunk or internal view of transmission electron microscopy analysis. These abnormal tracheae were not fully filled with gas and accompanied by a reduction in tracheal width, which are characteristic phenotypes of tracheal aECM defects. Furthermore, in the hemimetabolous brown planthopper (BPH) Nilaparvata lugens, downregulation of NlCPAP1‐N (a homolog of mtg) also led to the formation of abnormal tracheal chitin spirals and death. These results suggest that mtg and its homolog are involved in the proper organization of the tracheal aECMs in flies and BPH, and that this function may be conserved in insects.

中文翻译：

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心智参与果蝇和 Nilaparvata lugens 气管顶端细胞外基质组织的差距

气管顶端细胞外基质 (aECM) 对气管腔的扩张至关重要，并支持管腔的正常结构，以保证昆虫的空气进入和循环。尽管已经发现一些表皮蛋白参与了 aECM 的组织，但仍然存在一些未确定的因素。在这里，我们发现介意间隙（Mtg）是一种预测的几丁质结合蛋白，是模型全代谢昆虫黑腹果蝇气道管顶端几丁质基质的正常形成所必需的。与几丁质相似，Mtg 蛋白在果蝇气管的气管背干中呈线性排列。气管中mtg表达的降低严重影响了幼虫的生存能力，并导致一些幼虫出现气管甲壳素螺旋缺陷。mtg 突变体的分析表明，mtg 是胚胎气管正常发育所必需的。在气管背干的侧视图或透射电子显微镜分析的内部视图中发现了一些 mtg 突变体胚胎的不规则绦虫褶皱。这些异常气管未完全充满气体并伴有气管宽度减小，这是气管 aECM 缺陷的特征表型。此外，在半代谢的褐飞虱 (BPH) Nilaparvata lugens 中，NlCPAP1-N（mtg 的同系物）的下调也导致异常气管几丁质螺旋的形成和死亡。这些结果表明 mtg 及其同源物参与了苍蝇和 BPH 气管 aECM 的正确组织，并且该功能在昆虫中可能是保守的。在气管背干的侧视图或透射电子显微镜分析的内部视图中发现了一些 mtg 突变体胚胎的不规则绦虫褶皱。这些异常气管未完全充满气体并伴有气管宽度减小，这是气管 aECM 缺陷的特征表型。此外，在半代谢的褐飞虱 (BPH) Nilaparvata lugens 中，NlCPAP1-N（mtg 的同系物）的下调也导致异常气管几丁质螺旋的形成和死亡。这些结果表明 mtg 及其同源物参与了苍蝇和 BPH 气管 aECM 的正确组织，并且该功能在昆虫中可能是保守的。在气管背干的侧视图或透射电子显微镜分析的内部视图中发现了一些 mtg 突变体胚胎的不规则绦虫褶皱。这些异常气管未完全充满气体并伴有气管宽度减小，这是气管 aECM 缺陷的特征表型。此外，在半代谢的褐飞虱 (BPH) Nilaparvata lugens 中，NlCPAP1-N（mtg 的同系物）的下调也导致形成异常的气管几丁质螺旋和死亡。这些结果表明 mtg 及其同源物参与了苍蝇和 BPH 气管 aECM 的正确组织，并且该功能在昆虫中可能是保守的。