Division of Plant Science and Technology, University of Missouri, Columbia, MO 65211, USA.
Institution of Quality Standard and Testing Technology for Agro-Product, Shandong Academy of Agricultural Science, Jinan 250100, China.
Molecules. 2022 Sep 15;27(18):6017. doi: 10.3390/molecules27186017.
The transforming growth factor-β (TGF-β) superfamily encodes a large group of proteins, including TGF-β isoforms, bone morphogenetic proteins and activins that act through conserved cell-surface receptors and signaling co-receptors. TGF-β signaling in insects controls physiological events, including growth, development, diapause, caste determination and metamorphosis. In this study, we used the red flour beetle, Tribolium castaneum, as a model species to investigate the role of the type I TGF-β receptor, saxophone (Sax), in mediating development. Developmental and tissue-specific expression profiles indicated Sax is constitutively expressed during development with lower expression in 19- and 20-day (6th instar) larvae. RNAi knockdown of Sax in 19-day larvae prolonged developmental duration from larvae to pupae and significantly decreased pupation and adult eclosion in a dose-dependent manner. At 50 ng dsSax/larva, Sax knockdown led to an 84.4% pupation rate and 46.3% adult emergence rate. At 100 ng and 200 ng dsSax/larva, pupation was down to 75.6% and 50%, respectively, with 0% adult emergence following treatments with both doses. These phenotypes were similar to those following knockdowns of 20-hydroxyecdysone (20E) receptor genes, ecdysone receptor (EcR) or ultraspiracle protein (USP). Expression of 20E biosynthesis genes disembodied and spookier, 20E receptor genes EcR and USP, and 20E downstream genes BrC and E75, were suppressed after the Sax knockdown. Topical application of 20E on larvae treated with dsSax partially rescued the dsSax-driven defects. We can infer that the TGF-β receptor gene Sax influences larval-pupal-adult development via 20E signaling in T. castaneum.
转化生长因子-β（TGF-β）超家族编码了一大组蛋白质，包括 TGF-β 同工型、骨形态发生蛋白和激活素，它们通过保守的细胞表面受体和信号共受体发挥作用。昆虫中的 TGF-β信号控制着包括生长、发育、休眠、 caste 决定和变态在内的生理事件。在这项研究中，我们使用红粉甲虫（Tribolium castaneum）作为模型物种，研究了 I 型 TGF-β受体 saxophone（Sax）在介导发育中的作用。发育和组织特异性表达谱表明，Sax 在发育过程中持续表达，在 19 日龄和 20 日龄（6 龄期）幼虫中表达水平较低。在 19 日龄幼虫中，Sax 的 RNAi 敲低延长了从幼虫到蛹的发育时间，并以剂量依赖性方式显著降低了蛹化和成虫羽化率。在 50ng dsSax/幼虫时，Sax 敲低导致 84.4%的蛹化率和 46.3%的成虫出现率。在 100ng 和 200ng dsSax/幼虫时，蛹化率分别下降到 75.6%和 50%，两个剂量处理后成虫均未出现。这些表型与 20-羟蜕皮激素（20E）受体基因、蜕皮激素受体（EcR）或超螺蛋白（USP）敲低后的表型相似。在 Sax 敲低后，20E 生物合成基因 disembodied 和 spookier、20E 受体基因 EcR 和 USP 以及 20E 下游基因 BrC 和 E75 的表达均受到抑制。在幼虫上局部施用 20E 可部分挽救 dsSax 驱动的缺陷。我们可以推断，TGF-β 受体基因 Sax 通过 T. castaneum 中的 20E 信号影响幼虫-蛹-成虫的发育。
