β-防御素是天然免疫系统中一类重要的抗菌肽，其在生物体抵抗外界病原微生物感染过程中起着非常重要的作用。最近，中国科学院水生生物研究所桂建芳研究员主持的实验室从石斑鱼中克隆鉴定出一个同时在垂体和精巢中表达的β-防御素，这是首次发现防御素共同存在于脊椎动物的垂体和精巢中。

研究发现，在石斑鱼由雌向雄转变的性逆转进程中，该β-防御素在性腺中的表达不断上调；序列分析表明，该β-防御素启动子上有一个特异于垂体表达的POU1F1a结合位点和一个特异于精巢表达的SRY结合位点；体外和体内抗菌实验均表明，该β-防御素具有抑制革兰氏阴性菌生长的作用，且该作用与盐离子浓度相关；体外抗病毒实验还揭示出其抗病毒作用。

以上发现意味着鱼类β-防御素可能在天然免疫和生殖内分泌调控中起了重要作用，从而打开了认知β-防御素在生殖内分泌调控中功能作用的大门。

该研究得到国家基础研究973计划和国家重点基金等项目的资助，主要是由博士研究生金俊琰等完成，研究论文12月20日在PLoS ONE在线发表。

原文出处：

PLoS ONE    doi:10.1371/journal.pone.0012883

Antibacterial and Antiviral Roles of a Fish β-Defensin Expressed Both in Pituitary and Testis

Jun-Yan Jin, Li Zhou, Yang Wang, Zhi Li, Jiu-Gang Zhao, Qi-Ya Zhang, Jian-Fang Gui*

State Key Laboratory of Freshwater Ecology and Biotechnology, Wuhan Center for Developmental Biology, Institute of Hydrobiology, Graduate School of the Chinese Academy of Sciences, Chinese Academy of Sciences, Wuhan, China

Abstract

Defensins are a group of cationic peptides that exhibit broad-spectrum antimicrobial activity. In this study, we cloned and characterized a β-defensin from pituitary cDNA library of a protogynous hermaphroditic orange-spotted grouper (Epinephelus coioides). Interestingly, the β-defensin was shown to be dominantly expressed in pituitary and testis by RT-PCR and Western blot analysis, and its transcript level is significantly upregulated in reproduction organs from intersexual gonad to testis during the natural and artificial sex reversal. Promoter sequence and the responsible activity region analyses revealed the pituitary-specific POU1F1a transcription binding site and testis-specific SRY responsible site, and demonstrated that the pituitary-specific POU1F1a transcription binding site that locates between ?180 and ?208 bp is the major responsible region of grouper β-defensin promoter activity. Immunofluorescence localization observed its pituicyte expression in pituitary and spermatogonic cell expression in testis. Moreover, both in vitro antibacterial activity assay of the recombinant β-defensin and in vivo embryo microinjection of the β-defensin mRNA were shown to be effective in killing Gram-negative bacteria. And, its antiviral role was also demonstrated in EPC cells transfected with the β-defensin construct. Additionally, the antibacterial activity was sensitive to concentrations of Na+, K+, Ca2+ and Mg2+. The above intriguing findings strongly suggest that the fish β-defensin might play significant roles in both innate immunity defense and reproduction endocrine regulation.