Gardner L, Anderson T, Place A R, Dixon B, Elizur A
Bribie Island Aquaculture Research Centre, Department of Primary Industries and Fisheries, PO Box 2066, Woorim, Queensland 4507, Australia.
J Steroid Biochem Mol Biol. 2005 Apr;94(5):395-404. doi: 10.1016/j.jsbmb.2004.12.045. Epub 2005 Mar 23.
Sequential hermaphroditism is a common reproductive strategy in many teleosts. Steroid production is known to mediate both the natural and induced sex change, yet beyond this the physiology directing this process has received little attention. Cytochrome P450 aromatase is a key enzyme in the hormonal pathway catalysing the conversion of sex steroids, androgens to oestrogens, and thus is highly relevant to the process of sex change. This study reports the isolation of cDNA sequences for aromatase isoforms CYP19A1 and CYP19A2 from teleost species representing three forms of sexual hermaphroditism: Lates calcarifer (protandry), Cromileptes altivelis (protogyny), and Gobiodon histrio (bi-directional). Deduced amino acid analysis of these isoforms with other reported isoforms from gonochoristic (single sex) teleosts revealed 56-95% identity within the same isoform while only 48-65% identity between isoforms irrespective of species and sexual strategy. Phylogenetic analysis supported this result separating sequences into isoform exclusive clades in spite of species apparent evolutionary distance. Furthermore, this study isolates 5' flanking regions of all above genes and describes putative cis-acting elements therein. Elements identified include steroidogenic factor 1 binding site (SF-1), oestrogen response element (ERE), progesterone response element (PRE), androgen response element (ARE), glucocorticoid response elements (GRE), peroxisome proliferator-activated receptor alpha/retinoid X receptor alpha heterodimer responsive element (PPARalpha/RXRalpha), nuclear factor kappabeta (NF-kappabeta), SOX 5, SOX 9, and Wilms tumor suppressor (WTI). A hypothetical in vivo model was constructed for both isoforms highlighting potential roles of these putative cis-acting elements with reference to normal function and sexual hermaphroditism.
序列性雌雄同体现象是许多硬骨鱼类常见的繁殖策略。已知类固醇生成介导自然和诱导性别的转变，但除此之外，指导这一过程的生理学机制很少受到关注。细胞色素P450芳香化酶是激素途径中的关键酶，催化性类固醇雄激素向雌激素的转化，因此与性别转变过程高度相关。本研究报道了从代表三种性雌雄同体形式的硬骨鱼类物种中分离出芳香化酶同工型CYP19A1和CYP19A2的cDNA序列：尖吻鲈（雄性先熟）、驼背鲈（雌性先熟）和史氏腔吻鳕（双向性）。将这些同工型与其他已报道的雌雄异体（单性）硬骨鱼类的同工型进行推导氨基酸分析，结果显示同一同工型内的同一性为56 - 95%，而异工型之间的同一性仅为48 - 65%，与物种和性策略无关。系统发育分析支持了这一结果，尽管物种间存在明显的进化距离，但序列仍被分为同工型专属的进化枝。此外，本研究分离出了上述所有基因的5'侧翼区域，并描述了其中假定的顺式作用元件。鉴定出的元件包括类固醇生成因子1结合位点（SF-1）、雌激素反应元件（ERE）、孕激素反应元件（PRE）、雄激素反应元件（ARE）、糖皮质激素反应元件（GRE）、过氧化物酶体增殖物激活受体α/视黄酸X受体α异二聚体反应元件（PPARα/RXRα）、核因子κβ（NF-κβ）、SOX 5、SOX 9和威尔姆斯瘤抑制因子（WTI）。针对这两种同工型构建了一个假设的体内模型，参照正常功能和性雌雄同体现象突出了这些假定顺式作用元件的潜在作用。
