Smith C R, Morandin C, Noureddine M, Pant S
Department of Biology, Earlham College, Richmond, IN, USA.
Centre of Excellence in Biological Interactions, Department of Biosciences, University of Helsinki, Helsinki, Finland.
J Evol Biol. 2018 Apr;31(4):516-529. doi: 10.1111/jeb.13238. Epub 2018 Feb 2.
Much of the variation among insects is derived from the different ways that chitin has been moulded to form rigid structures, both internal and external. In this study, we identify a highly conserved expression pattern in an insect-only gene family, the Osiris genes, that is essential for development, but also plays a significant role in phenotypic plasticity and in immunity/toxicity responses. The majority of Osiris genes exist in a highly syntenic cluster, and the cluster itself appears to have arisen very early in the evolution of insects. We used developmental gene expression in the fruit fly, Drosophila melanogaster, the bumble bee, Bombus terrestris, the harvester ant, Pogonomyrmex barbatus, and the wood ant, Formica exsecta, to compare patterns of Osiris gene expression both during development and between alternate caste phenotypes in the polymorphic social insects. Developmental gene expression of Osiris genes is highly conserved across species and correlated with gene location and evolutionary history. The social insect castes are highly divergent in pupal Osiris gene expression. Sets of co-expressed genes that include Osiris genes are enriched in gene ontology terms related to chitin/cuticle and peptidase activity. Osiris genes are essential for cuticle formation in both embryos and pupae, and genes co-expressed with Osiris genes affect wing development. Additionally, Osiris genes and those co-expressed seem to play a conserved role in insect toxicology defences and digestion. Given their role in development, plasticity, and protection, we propose that the Osiris genes play a central role in insect adaptive evolution.
昆虫之间的许多差异源自几丁质被塑造成内部和外部刚性结构的不同方式。在本研究中，我们在一个仅存在于昆虫中的基因家族——奥西里斯基因中，识别出一种高度保守的表达模式，该模式对发育至关重要，同时在表型可塑性以及免疫/毒性反应中也发挥着重要作用。大多数奥西里斯基因存在于一个高度共线的基因簇中，而且这个基因簇本身似乎在昆虫进化的早期就已出现。我们利用果蝇、熊蜂、收获蚁和木工蚁的发育基因表达，来比较奥西里斯基因在发育过程中以及多态性社会昆虫不同等级表型之间的表达模式。奥西里斯基因的发育基因表达在物种间高度保守，并且与基因位置和进化历史相关。社会性昆虫的等级在蛹期奥西里斯基因表达上差异很大。包含奥西里斯基因的共表达基因集在与几丁质/角质层和肽酶活性相关的基因本体术语中富集。奥西里斯基因对胚胎和蛹的角质层形成至关重要，与奥西里斯基因共表达的基因影响翅膀发育。此外，奥西里斯基因及其共表达基因似乎在昆虫毒理学防御和消化中发挥着保守作用。鉴于它们在发育、可塑性和保护方面的作用，我们认为奥西里斯基因在昆虫适应性进化中发挥着核心作用。
