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

在五种甲壳类动物中，发现两个相邻的Hox基因Ubx和Antp的转录产物大量表达。在水蚤中，双链Ubx/Antp mRNA均未产生显著水平的Ubx或Antp。另一方面，在Artemia中，双反子mRNA只产生Ubx，取代了单反子Ubx mRNA的作用。通过这种方式，两种现存的枝足动物的多种转录后控制机制ms可以被视为防止狐狸基因融合的潜在有害后果。D. magna aryl hydrocarbon receptor nuclear translocator （ARNT）在缺乏ARNT的小鼠Hepa-c4细胞中的表达弥补了缺氧反应的缺失。D. magna ARNT在胚胎发育中后期各组织中均有表达。相比之下，成年水蚤中ARNT的表达仅限于胸肢的表骺，这表明ARNT仅在缺氧反应中起作用。幼崽激素（JH）激动剂吡丙醚和苯醚威对新生水蚤卵黄蛋白原基因的表达有强烈的抑制作用。大鼠卵黄原基因之间2.6 kb的基因间区含有类似于已知的jh响应元件和表皮激素响应元件的序列。分离并鉴定了秀丽隐杆线虫性别决定因子CPEB的D. magna cDNA同源物。水蚤暴露于JH后，CPEB mRNA的数量减少了七分之一。CPEB mRNA在水蚤卵黄形成阶段的生殖系细胞中特异性表达。水蚤暴露于JH诱导的血红蛋白亚基组成与缺氧诱导的血红蛋白亚基组成不同。

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.