Molecular mechanisms of morphogenesis and response to environmental cues in cladoceran crustaceans

在5种甲壳类动物中发现了两个相邻的HOX基因Ubx和ANTP的转录读出产物在支脚类和软体动物中的大量表达。在水蚤中，双顺反子Ubx/ANTP mRNA不产生显著的Ubx或ANTP水平。另一方面，在卤虫中，双顺反子mRNA只产生Ubx，并取代了单顺反子Ubx mRNA的作用。通过这种方式，现存的两个分支足类动物中的多个转录后调控机制可以被视为防止Fox基因融合的潜在有害后果。在Arnt缺失的小鼠HEPA-C4细胞中表达D.Magna芳烃受体核转运子(ARNT)导致对缺氧反应丧失的补偿。在胚胎发育的中晚期，D.Magna Arnt在不同组织中表达。相反，Arnt在成虫体内的表达仅限于胸肢上足，这表明Arnt仅在低氧反应中起作用。保幼激素(JH)激动剂吡丙草醚和苯氧碳酸酯强烈抑制幼虫卵黄蛋白原基因的表达。大麦卵黄蛋白原基因之间2.6kb的基因间隔区含有与已知的JH反应元件和蜕皮激素反应元件相似的序列。分离并鉴定了线虫性别决定子CPEB的一个大核糖核酸同源基因。甲虫暴露于JH后，CPEB mRNA的量减少到七分之一。在卵黄形成阶段，CPEB基因在丝虫的生殖系细胞中特异表达。甲虫暴露JH诱导的血红蛋白亚基组成与低氧诱导的不同。

Abundant expression of transcriptional read through products of two adjacent Hox genes, Ubx and Antp, was found in five crustacean species of Branchiopoda and Malacostaraca. In Daphnia, bicistronic Ubx/Antp mRNA produced no significant level of either Ubx or ANTP. In Artemia, on the other hand, the bicistronic mRNA produced only Ubx, and replaced the role of monocistronic Ubx mRNA. In this way, multiple post-transcriptional control mechanic ms in two extant branchiopodans can be seen as preventing the potentially deleterious consequences of fox gene fusion.Expression of D. magna aryl hydrocarbon receptor nuclear translocator (ARNT) in ARNT-lacking mouse Hepa-c4 cells resulted in the compensation for the loss of hypoxia response. D. magna ARNT was expressed in various tissues at the middle to late stages of embryonic development. In contrast, expression of ARNT in adult daphnids was limited to the epipodites of thoracic limbs, suggesting that ARNT plays a role solely in hypoxia response. Juvenile hormone (JH) agonists, pyriproxyfen and fenoxycarb, strongly repressed the expression of vitellogenin genes in neonate daphnids. The intergenic region of 2.6 kb between the D. magna vitellogenin genes contained sequences resembling known JH-responsive and ecdysone-responsive elements. A D. magna cDNA homolog of CPEB, a sex-determinant in C. elegans, was isolated and characterized. Amount of CPEB mRNA was decreased to one seventh after exposure of daphnids to JH. CPEB mRNA was expressed specifically in germ line cells in daphnids at the stages of yolk formation. Subunit composition of hemoglobins induced by exposure of daphnids to JH was different from that of hemoglobins induced by hypoxia.