Department of Marine Bio-Materials & Aquaculture, Pukyong National University, Busan, 48513, South Korea.
Department of Marine Bio-Materials & Aquaculture, Pukyong National University, Busan, 48513, South Korea.
Fish Shellfish Immunol. 2019 Oct;93:161-173. doi: 10.1016/j.fsi.2019.07.040. Epub 2019 Jul 15.
Two liver-expressed antimicrobial peptide 2 (LEAP2) isoforms were characterized in a primitive chondrostean sturgeon species, Acipenser baerii (Acipenseriformes). A. baerii LEAP2 isoforms represented essentially common structures shared by their vertebrate orthologs at both genomic (i.e., tripartite organization) and peptide (two conserved disulfide bonds) levels. A. baerii LEAP2 isoforms (designed LEAP2AB and LEAP2C, respectively) phylogenetically occupy the most basal position in the actinopterygian lineage and represent an intermediate character between teleostean and tetrapodian LEAP2s in the sequence alignment. Molecular phylogenetic analysis including LEAP2s from extant primitive fish species indicated that the evolutionary origin of ancestral LEAP2 in vertebrate groups should date back to earlier than the actinopterygian-sarcopterygian split. Gene expression assays under both basal and stimulated conditions suggested that A. baerii LEAP2 isoforms have undergone substantial subfunctionalization in tissue distribution pattern, developmental/ontogenetic expression, and immune responses. LEAP2AB showed a predominant liver expression, while LEAP2C exhibited the highest level of expression in the intestine. LEAP2C was a more dominantly expressed isoform during embryonic development and prelarval ontogeny. The LEAP2AB isoform is more closely associated with innate immune response to microbial invasion, compared with LEAP2C, as evidenced by results from LPS, poly(I:C) and Aeromonas hydrophila challenges. Synthetic mature peptides of LEAP2AB displayed a more potent antimicrobial activity than did LEAP2C. Data from this study could be useful not only to provide deeper insights into the evolutionary mechanism of LEAP2 in the actinopterygian lineage but also to better understand the innate immunity of this commercially important chondrostean species.
两种肝表达抗菌肽 2（LEAP2）同工型在原始软骨硬鳞鱼类，施氏鲟（鲟形目）中得到了鉴定。A. baerii LEAP2 同工型在基因组（即三分体结构）和肽（两个保守的二硫键）水平上与它们的脊椎动物同源物基本具有共同结构。A. baerii LEAP2 同工型（分别设计为 LEAP2AB 和 LEAP2C）在硬骨鱼谱系中占据最基础的位置，在序列比对中代表了硬骨鱼类和四足动物 LEAP2 之间的中间特征。包括现存原始鱼类 LEAP2 在内的分子系统发育分析表明，脊椎动物群中祖先 LEAP2 的进化起源应该可以追溯到硬骨鱼-肉鳍鱼分裂之前。在基础和刺激条件下的基因表达分析表明，A. baerii LEAP2 同工型在组织分布模式、发育/个体发生表达和免疫反应方面经历了实质性的亚功能化。LEAP2AB 主要在肝脏中表达，而 LEAP2C 在肠道中表达水平最高。LEAP2C 在胚胎发育和幼鱼个体发生过程中表达水平更高。与 LEAP2C 相比，LEAP2AB 同工型与先天免疫对微生物入侵的反应更为密切相关，这一结果通过 LPS、poly(I:C)和嗜水气单胞菌的挑战得到了证实。LEAP2AB 的成熟肽显示出比 LEAP2C 更强的抗菌活性。本研究的数据不仅有助于深入了解 LEAP2 在硬骨鱼谱系中的进化机制，而且有助于更好地了解这种具有商业重要性的软骨鱼类的先天免疫。
