Hormone-related genes heterochronically and modularly regulate neotenic differentiation in termites
Hormone-related genes heterochronically and modularly regulate neotenic differentiation in termites
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激素相关基因异时性和模块化调节白蚁幼态分化
DOI：
10.1016/j.ydbio.2022.02.012
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发表时间：
2022
影响因子：
2.7
通讯作者：
Miura Toru
中科院分区：
文献类型：
--
作者：
Oguchi Kohei;Koshikawa Shigeyuki;Miura Toru
社会性昆虫的种姓发展需要蜕皮和变态在胚后发育过程中的协调。在白蚁中，即，在半变态真社会性昆虫中，种姓命运在胚后发育期间决定。然而，目前还没有完全了解蜕皮/变态的机制是如何调节的过程中，生殖和不育种姓之间的分化。在白蚁中，只有从有翅类衍生的生殖后代是成虫，而其他不育种姓（包括发育末期的士兵种姓）基本上是幼虫或幼虫。此外，当原来的蜂王和蜂王死亡或衰老时出现的补充生殖体，表现出幼虫的特征，如无翅，被称为幼态持续。因此，幼态持续期是幼虫还是成虫的问题仍有争议。在这项研究中，通过诱导雌性幼态分化的湿木白蚁Hodotermopsis sjostedti，形态调查连同保幼激素（JH）的定量和表达/功能分析的基因负责蜕皮和/或变态进行。JH滴度和下游基因之一（Kr-h1）的表达显示暂时降低，但在蜕皮进入幼态前增加，而在成虫蜕皮中持续降低（即，有翅分化）。相反，蜕皮激素相关基因（EcRandE 93）在幼态和有翅分化中均上调，表明蜕皮激素和JH的异时作用导致幼态分化。此外，通过反向遗传实验的表达分析表明，EcRandE 93在生殖器胸骨（EcRandE 93）和卵巢（E93）中特异性上调，并且是成虫性状发育所必需的。这些结果表明，由此产生的马赛克表型的女性幼态是由于模块化的反应，不同的身体部位激素的行动。
Caste development in social insects requires the coordination of molting and metamorphosis during postembryonic development. In termites, i.e., hemimetabolous eusocial insects, caste fate is determined during postembryonic development. However, it is not fully understood how the mechanisms of molting/metamorphosis are regulated in the course of differentiation between reproductive and sterile castes. In termites, only reproductives derived from alates are imagos and other sterile castes (including developmentally-terminal soldier caste) are basically juveniles or nymphs. Furthermore, supplementary reproductives that appear when the original queens and kings die or become senescent, exhibit larval features such as winglessness, and are called neotenics. Therefore, the question of whether neotenics are larvae or imagos is still under debate. In this study, by inducing female neotenic differentiation in a damp-wood termiteHodotermopsis sjostedti, morphological investigations together with juvenile hormone (JH) quantification and expression/functional analyses of genes responsible for molting and/or metamorphosis were carried out. JH titer and expression of one of the downstream genes (Kr-h1) were shown to be temporarily lowered, but increased just prior to the molt into neotenics, while consistently lowered in imaginal molt (i.e., alate differentiation). In contrast, ecdysone-related genes (EcRandE93) were upregulated at both neotenic and alate differentiation, suggesting that the heterochronic actions of ecdysone and JH lead the neotenic differentiation. Moreover, expression analyses, supported by reverse genetic experiments, showed thatEcRandE93were specifically upregulated in genital sternites (EcRandE93) and ovaries (E93) and required for the development of imaginal characters. These results suggest that the resultant mosaic phenotype of female neotenics is due to modular responses of different body parts to hormonal actions.