Luckenbach John Adam, Early Lea Ware, Rowe Ashlee H, Borski Russell John, Daniels Harry V, Godwin John
Department of Zoology, North Carolina State University, Raleigh, North Carolina 27695-7617, USA.
J Exp Zool A Comp Exp Biol. 2005 Aug 1;303(8):643-56. doi: 10.1002/jez.a.198.
Aromatase cytochrome P450 (P450arom) is the enzyme complex responsible for conversion of androgens to estrogens in vertebrates. Consequently, in some fishes its activity appears critical to ovarian differentiation. Southern flounder (Paralichthys lethostigma) is a commercially important flatfish in which females grow larger than males and sex determination is temperature sensitive. Through cloning of the P450arom gene in ovary and quantitative reverse transcription-polymerase chain reaction, we developed a biomarker for early female differentiation in southern flounder. The deduced amino acid sequence for southern flounder P450arom is similar to other teleosts. Comparison of P450arom intron sequences from fish of different populations revealed substantial inter-individual variation. Adult ovary and spleen exhibited high levels of P450arom mRNA, while P450arom mRNA was only weakly detected in testes. Brain, liver, intestine, kidney, gill, muscle, and heart showed little or no P450arom mRNA expression. Gonads of wild and hatchery-produced juvenile flounder of sizes spanning the period of sex differentiation initially exhibited low levels of P450arom mRNA followed by increases in some individuals and bifurcation into two clearly segregated groups (i.e., putative males and females) beginning at approximately 65 mm in total length. Gonadal histology confirmed predictions of sex based on P450arom expression in juvenile flounder, demonstrating that the patterns of P450arom expression observed relate to sex-specific differentiation. This research represents a unique approach to assessing sex differentiation in a natural population, and a powerful technique for better understanding mechanisms of flounder sex determination and rapidly defining conditions for controlling sex for aquaculture.
芳香化酶细胞色素P450（P450arom）是一种负责脊椎动物雄激素向雌激素转化的酶复合体。因此，在一些鱼类中，其活性对卵巢分化似乎至关重要。南方鲆（Paralichthys lethostigma）是一种具有重要商业价值的比目鱼，雌性个体比雄性个体生长得更大，且性别决定对温度敏感。通过克隆卵巢中的P450arom基因并进行定量逆转录-聚合酶链反应，我们开发了一种用于南方鲆早期雌性分化的生物标志物。南方鲆P450arom推导的氨基酸序列与其他硬骨鱼相似。对不同种群鱼类的P450arom内含子序列进行比较，发现个体间存在显著差异。成年卵巢和脾脏中P450arom mRNA水平较高，而在睾丸中仅微弱检测到P450arom mRNA。脑、肝、肠、肾、鳃、肌肉和心脏几乎没有或未检测到P450arom mRNA表达。野生和孵化场培育的处于性别分化期的不同大小的南方鲆幼鱼性腺，最初P450arom mRNA水平较低，随后一些个体中该水平升高，并在全长约65毫米时分为两个明显分开的组（即假定的雄性和雌性）。性腺组织学证实了基于南方鲆幼鱼P450arom表达的性别预测，表明观察到的P450arom表达模式与性别特异性分化有关。这项研究代表了一种评估自然种群性别分化的独特方法，也是一种强大的技术，有助于更好地理解鲆性别决定机制，并快速确定水产养殖中控制性别的条件。
