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

两个相邻的Hox基因，Ubx和Antp，转录通读产物的丰富表达，被发现在五种甲壳动物的鳃足类和软足类。在水蚤中，双顺反子Ubx/Antp mRNA没有产生显著水平的Ubx或ANTP。另一方面，在卤虫中，双顺反子mRNA仅产生Ubx，并取代了单顺反子Ubx mRNA的作用。以这种方式，在两种现存的鳃足动物中的多种转录后控制机制可以被看作是防止狐狸基因融合的潜在有害后果。大芳香烃受体核转位蛋白（ARNT）缺失的小鼠Hepa-c4细胞中的ARNT导致对缺氧反应丧失的补偿。D. magna ARNT在胚胎发育的中晚期在各种组织中表达。相反，ARNT在成年水蚤中的表达仅限于胸肢的上足，表明ARNT仅在缺氧反应中起作用。保幼激素（JH）激动剂，吡丙醚和苯氧威，强烈抑制新生水蚤卵黄蛋白原基因的表达。D. magna卵黄蛋白原基因含有类似于已知的JH反应和蜕皮激素反应元件的序列。了dna CPEB的magna cDNA同源物，是C. elegans的分离和表征。JH处理后，CPEB mRNA的表达量下降至对照组的1/7。CPEB mRNA在卵黄形成阶段的生殖细胞中特异性表达。JH诱导的水蚤血红蛋白亚基组成与缺氧诱导的不同。

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.