Duffy Tara A, Picha Matthew E, Won Eugene T, Borski Russell J, McElroy Anne E, Conover David O
School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794-5000, USA.
J Exp Zool A Ecol Genet Physiol. 2010 Aug 1;313(7):421-31. doi: 10.1002/jez.612.
Cytochrome P450 aromatase (P450arom), an enzyme that converts testosterone to 17beta-estradiol, is an important mediator of sex determination in teleosts with genetic sex determination (GSD) and temperature-dependent sex determination (TSD). We compared the ontogenetic expression of P450arom in two populations of Atlantic silversides, Menidia menidia, which exhibit TSD (South Carolina) or GSD (Nova Scotia, Canada) using quantitative, real-time polymerase chain reaction (qRT-PCR). Embryos and newly hatched larvae were reared at an intermediate sex ratio-producing temperature (21 degrees C), and older larvae and juveniles were reared at temperatures that feminize (15 degrees C) and masculinize (28 degrees C) to assess the temperature response of P450arom during development. Before sex determination, embryos and newly-hatched larvae displayed negligible P450arom expression, indicating minimal upregulation of this gene before sex determination. Gene expression increased in both populations during sex differentiation. Nova Scotia fish with GSD exhibited presumptive male- and female-like expression levels during early sex differentiation that were not influenced by temperature. South Carolina fish displayed low levels of expression at 28 degrees C with significantly heightened expression in some individuals at 15 degrees C, indicating that P450arom is temperature sensitive in the population with TSD. Populations also differed in the timing and maximal levels of P450arom expression, with fish from Nova Scotia exhibiting both the highest and earliest increase in expression in presumptive females. Our results support the hypothesis that P450arom is involved in female sex differentiation in this species, but is only responsive to temperature in M. menidia populations that exhibit TSD.
细胞色素P450芳香化酶（P450arom）是一种将睾酮转化为17β-雌二醇的酶，在具有遗传性别决定（GSD）和温度依赖性性别决定（TSD）的硬骨鱼中，它是性别决定的重要调节因子。我们使用定量实时聚合酶链反应（qRT-PCR）比较了两个大西洋银汉鱼种群（Menidia menidia）中P450arom的个体发育表达情况，这两个种群分别表现出TSD（南卡罗来纳州）或GSD（加拿大新斯科舍省）。胚胎和新孵化的幼体在产生中间性别比例的温度（21摄氏度）下饲养，而较大的幼体和幼鱼则在使性别雌性化（15摄氏度）和雄性化（28摄氏度）的温度下饲养，以评估发育过程中P450arom对温度的反应。在性别决定之前，胚胎和新孵化的幼体中P450arom的表达可以忽略不计，这表明该基因在性别决定之前极少上调。在性别分化过程中，两个种群的基因表达均增加。具有GSD的新斯科舍省鱼类在早期性别分化过程中表现出类似雄性和雌性的假定表达水平，且不受温度影响。南卡罗来纳州的鱼类在28摄氏度时表达水平较低，而在15摄氏度时一些个体的表达显著升高，这表明在具有TSD的种群中P450arom对温度敏感。两个种群在P450arom表达的时间和最高水平上也存在差异，新斯科舍省的鱼类在假定雌性中表达增加的幅度最大且最早。我们的结果支持这样的假设，即P450arom参与了该物种的雌性性别分化，但仅在表现出TSD的大西洋银汉鱼种群中对温度有反应。
