Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan;
Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8566, Japan.
Proc Natl Acad Sci U S A. 2022 Mar 1;119(9). doi: 10.1073/pnas.2114773119.
Insects comprise over half of the described species, and the acquisition of metamorphosis must have contributed to their diversity and prosperity. The order Odonata (dragonflies and damselflies) is among the most-ancestral insects with drastic morphological changes upon metamorphosis, in which understanding of the molecular mechanisms will provide insight into the evolution of incomplete and complete metamorphosis in insects. In order to identify metamorphosis-related genes in Odonata, we performed comprehensive RNA-sequencing of the blue-tailed damselfly at different developmental stages. Comparative RNA-sequencing analyses between nymphs and adults identified eight nymph-specific and seven adult-specific transcripts. RNA interference (RNAi) of these candidate genes demonstrated that three transcription factors, (), , and play important roles in metamorphosis of both and a phylogenetically distant dragonfly, is essential for adult morphogenesis, and RNAi of induced precocious metamorphosis in epidermis via up-regulation of Precocious metamorphosis was also induced by RNAi of the juvenile hormone receptor (), confirming that the regulation of metamorphosis by the MEKRE93 (Met-Kr-h1-E93) pathway is conserved across diverse insects including the basal insect lineage Odonata. Notably, RNAi of produced unique grayish pigmentation on the nymphal abdominal epidermis. Survey of downstream genes for , , and uncovered that unlike other insects, regulates a substantial number of nymph-specific and adult-specific genes independently of and These findings highlight the importance of functional changes and rewiring of the transcription factors , , and in the evolution of insect metamorphosis.
昆虫纲占已描述物种的一半以上，而变态的获得必然促进了它们的多样性和繁荣。蜻蜓目（蜻蜓和豆娘）是最古老的昆虫之一，在变态过程中经历了剧烈的形态变化，对其分子机制的理解将有助于深入了解昆虫不完全变态和完全变态的进化。为了鉴定蜻蜓目中与变态相关的基因，我们对不同发育阶段的蓝尾蜻蜓进行了全面的 RNA-seq 测序。若比较若比较幼虫和成虫的 RNA-seq 分析，我们鉴定出 8 个幼虫特异性和 7 个成虫特异性转录本。对这些候选基因进行 RNA 干扰（RNAi）实验表明，三个转录因子 （） 、 （） 和 （） 在 和种亲缘关系较远的蜻蜓的变态中发挥重要作用， 对于成虫形态发生是必需的，而 的 RNAi 则通过上调 诱导表皮过早变态，早龄激素受体 （） 的 RNAi 也证实了 MEKRE93（Met-Kr-h1-E93）途径对变态的调控在包括蜻蜓目在内的各种基础昆虫谱系中是保守的。值得注意的是， 的 RNAi 在幼虫腹部表皮上产生了独特的灰化色素沉着。对 、 和 的下游基因进行调查发现，与其他昆虫不同， 独立于 和 调控大量幼虫特异性和成虫特异性基因。这些发现强调了转录因子 （） 、 （） 和 （） 在昆虫变态进化中的功能变化和重布线的重要性。
