Although recent studies have revealed its involvement in fish reproduction, the physiological role of neurokinin B (NKB), which is encoded by the tachykinin 3 (tac3) gene, is still largely unclear in teleosts, with most researches on the orders Perciformes and Cypriniformes. In the current study we identified the tac3 gene in a representative species of Pleuronectiformes, the half-smooth tongue sole. The full-length cDNA sequence of tongue sole tac3 was 742 base pairs (bp) in length with an open reading frame of 372 bp that encoded a 123-amino acids preprohormone. The TAC3 precursor contained NKB and an additional peptide NKB-related peptide (NKBRP), both of which had an –FVGLM motif at the C-termini. Tissue distribution analysis indicated that tac3 transcripts were highly expressed in the brain, intestine and gonads of both sexes, and to a lesser extent in other tissues. Among various brain regions, tac3 transcripts were most abundant in the hypothalamus. In addition, the expression profiles of tac3 mRNA were also evaluated along the brain-pituitary-gonadal axis during tongue sole ovarian maturation. The brain tac3 mRNA levels remained unchanged, however, in both pituitary and ovary, the mRNA expression of tac3 increased significantly to the maximal levels at stage III and then declined back to basal levels. Taken together, our results encompass the first study reporting the existence of tac3 gene in a flatfish species and suggest its possible involvement in the control of reproduction in the half-smooth tongue sole.

尽管最近的研究表明其参与鱼类繁殖，但是由速激肽3（tac3）基因编码的神经激肽B（NKB）的生理作用在硬骨鱼中仍然不清楚，大多数研究都针对Perciformes和Cypriniformes。在当前的研究中，我们在半光滑舌底的截肢梭形菌的代表性物种中鉴定了tac3基因。舌根tac3的全长cDNA序列长度为742个碱基对（bp），具有372bp的开放阅读框，编码123个氨基酸的前激素。TAC3前体包含NKB和另外一个肽NKB相关肽（NKBRP），两者在C末端均具有–FVGLM基序。组织分布分析表明tac3转录本在男女的脑，肠和性腺中高表达，而在其他组织中表达较少。在不同的大脑区域中，下丘脑中tac3转录本最丰富。此外，还评估了舌头卵巢成熟过程中沿脑-垂体-性腺轴的tac3 mRNA的表达情况。脑tac3 mRNA的水平保持不变，但是在垂体和卵巢中，tac3的mRNA表达均显着增加至III期的最高水平，然后又下降至基础水平。综上所述，我们的结果涵盖了第一个报告tac3存在的研究。 基因在一个比目鱼物种中，并暗示其可能参与了半光滑舌tongue的繁殖控制。