Dias Renata O, Cardoso Christiane, Leal Camila S, Ribeiro Alberto F, Ferreira Clélia, Terra Walter R
Departamento de Bioquimica, Instituto de Quimica, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil.
Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, C.P. 11461, 05422-970 São Paulo, Brazil.
J Insect Physiol. 2019 Apr;114:1-9. doi: 10.1016/j.jinsphys.2019.02.002. Epub 2019 Feb 5.
Most insects have a peritrophic membrane (matrix) (PM) surrounding the food bolus. This structure, similarly to the cuticle, is mainly composed of chitin and proteins. The main proteins forming PM are known as peritrophins (PMP), whereas some of the cuticle proteins are the cuticle proteins analogous to peritrophins (CPAP). Both proteins are composed of one or more chitin binding peritrophin-A domain (CBD) and no other recognized domain. Furthermore, insects containing PM usually have two chitin synthase (CS) genes, one mainly expressed in carcass and the other in midgut. In this work we identified PMP, CPAP and CS genes in the genome of insects from the Polyneoptera, Paraneoptera and Holometabola cohorts and analyzed their expression profile in different species from each group. In agreement with the absence of PM, we observed less CBD-containing proteins and only one CS gene in the genome of Paraneoptera species, except for the Phthiraptera Pediculus humanus. The lack of PM in Paraneoptera species was also confirmed by the micrographs of the midgut of two Hemiptera species, Dysdercus peruvianus and Mahanarva fimbriolata which agreed with the RNA-seq data of both species. Our analyses also highlighted a higher number of CBD-containing proteins in Holometabola in relation to the earlier divergent Polyneoptera group, especially regarding the genes composed of more than three CBDs, which are usually associated to PM formation. Finally, we observed a high number of CBD-containing proteins being expressed in both midgut and carcass tissues of several species, which we named as ubiquitous-CBD-containing proteins (UCBP), as their function is unclear. We hypothesized that these proteins can be involved in both cuticle and PM formation or that they can be involved in immune response and/or tracheolae formation.
大多数昆虫都有一层围绕食物团的围食膜（基质）（PM）。这种结构与表皮类似，主要由几丁质和蛋白质组成。形成围食膜的主要蛋白质被称为围食膜蛋白（PMP），而一些表皮蛋白是与围食膜蛋白类似的表皮蛋白（CPAP）。这两种蛋白质都由一个或多个几丁质结合围食膜蛋白-A结构域（CBD）组成，没有其他公认的结构域。此外，含有围食膜的昆虫通常有两个几丁质合酶（CS）基因，一个主要在体表表达，另一个在中肠表达。在这项工作中，我们在多新翅类、副新翅类和全变态类昆虫的基因组中鉴定了PMP、CPAP和CS基因，并分析了它们在每组不同物种中的表达谱。与围食膜的缺失一致，我们观察到副新翅类物种的基因组中含CBD的蛋白质较少，并且只有一个CS基因，但虱目人虱除外。半翅目两个物种，即秘鲁红蝽和细纹玛绢金龟中肠的显微照片也证实了副新翅类物种中围食膜的缺失，这与这两个物种的RNA测序数据一致。我们的分析还强调，与早期分化的多新翅类群相比，全变态类中含CBD的蛋白质数量更多，特别是对于由三个以上CBD组成的基因，这些基因通常与围食膜的形成有关。最后，我们观察到一些物种的中肠和体表组织中都有大量含CBD的蛋白质表达，我们将其命名为普遍含CBD的蛋白质（UCBP），因为它们的功能尚不清楚。我们推测这些蛋白质可能参与表皮和围食膜的形成，或者它们可能参与免疫反应和/或微气管的形成。
