Department of Fishery Biology, Pukyong National University, Busan 608-737, Republic of Korea.
Fish Physiol Biochem. 2013 Apr;39(2):263-75. doi: 10.1007/s10695-012-9697-y. Epub 2012 Jul 28.
This study aims to investigate the genes encoding prolactin (PRL) and prolactin receptors (PRLR) and their tissue-specific expression in starry flounder Platichthys stellatus. Starry flounder PRL gene consisting of five exons encodes an ORF of 212 amino acid residue comprised of a putative signal peptide of 24 amino acids and a mature protein of 188 amino acids. It showed amino acid identities of 73 % with tuna Thunnus thynnus, 71 % with black porgy Acanthopagrus schlegelii, 69 % with Nile tilapia Oreochromis niloticus, 64 % with pufferfish Takifugu rubripes, 63 % with rainbow trout Oncorhynchus mykiss, and 60 % with mangrove rivulus Kryptolebias marmoratus. Phylogenetic analysis of piscine PRLs also demonstrated a similarity between starry flounder and other teleosts but with a broad distinction from non-teleost PRLs. PRLR gene consists of eight exons encoding a protein of 528 amino acid residues. It showed a similarity to the PRLR2 subtype as reflected by amino acid identities of 54 % with A. schlegelii, 48.1 % with K. marmoratus, 46.3 % with tilapia O. mossambicus, and 46.1 % with O. niloticus PRLR2 as compared to PRLR1 isoform having less than 30 % identities. While mRNA transcript corresponding to PRL was detected only from the pituitary, most of PRLR mRNA was detected in the gill, kidney, and intestine, with a small amount in the ovary. The level of PRL transcript progressively increased during 6 days of acclimation to freshwater and then decreased but stayed higher than that of seawater at 60 days of acclimation. An opposite pattern of changes including a decrease at the beginning of the acclimation but a slight increase in the level osmolality was found as adaptation continued. The results support the osmoregulatory role of PRL signaling in starry flounder.
本研究旨在探讨星斑川鲽（Platichthys stellatus）中编码催乳素（PRL）和催乳素受体（PRLR）的基因及其组织特异性表达。星斑川鲽 PRL 基因由五个外显子组成，编码一个由 212 个氨基酸残基组成的开放阅读框，包括一个假定的 24 个氨基酸的信号肽和一个由 188 个氨基酸组成的成熟蛋白。它与金枪鱼（Thunnus thynnus）的氨基酸同一性为 73%，与黑鲷（Acanthopagrus schlegelii）的氨基酸同一性为 71%，与尼罗罗非鱼（Oreochromis niloticus）的氨基酸同一性为 69%，与河豚（Takifugu rubripes）的氨基酸同一性为 64%，与虹鳟（Oncorhynchus mykiss）的氨基酸同一性为 63%，与红树林罗非鱼（Kryptolebias marmoratus）的氨基酸同一性为 60%。鱼类 PRLs 的系统发育分析也表明，星斑川鲽与其他硬骨鱼具有相似性，但与非硬骨鱼 PRLs 有很大的区别。PRLR 基因由八个外显子组成，编码一个由 528 个氨基酸残基组成的蛋白质。它与 PRLR2 亚型相似，与黑鲷的氨基酸同一性为 54%，与红树林罗非鱼的氨基酸同一性为 48.1%，与奥利亚罗非鱼的氨基酸同一性为 46.3%，与尼罗罗非鱼的氨基酸同一性为 46.1%，而与 PRLR1 同工型的氨基酸同一性小于 30%。虽然只从垂体中检测到与 PRL 相对应的 mRNA 转录本，但在鳃、肾脏和肠道中检测到大部分 PRLR mRNA，在卵巢中检测到少量 PRLR mRNA。在适应淡水的 6 天过程中，PRL 转录本的水平逐渐升高，然后降低，但在适应 60 天的过程中仍高于海水水平。适应过程中发现了一种相反的变化模式，包括适应开始时下降，但渗透压水平略有增加。结果支持 PRL 信号在星斑川鲽中的渗透压调节作用。
