瓦氏雅罗鱼耐碱性状相关分子标记的筛选

本研究以来自达里湖(碱水)和松花江(淡水)的瓦氏雅罗鱼(Leuciscus waleckii)杂交F2为实验材料,通过碱度耐受实验进行性状测定,以39对多态的EST-SSR和SSR为标记,对77个F2个体进行基因分型,根据Fisher确切概率法对F2基因型和耐碱性状进行关联分析。结果发现,有2个标记与耐碱性状显著相关(P0.05),其中1个标记为EST-SSR,从瓦氏雅罗鱼转录组数据库中调取该EST序列,基因注释结果显示该序列与团头鲂(Megalobrama amblycephala)低氧诱导因子HIF-3?基因、草鱼的低氧诱导因子HIF-4?基因具有很高的同源性。该基因的主要功能是参与鱼类的耐低氧反应过程,加强鱼类的耐低氧能力。本研究对于今后深入研究此功能基因的作用机制及培育适于盐碱水域养殖的鱼类新品种具有重要的意义。

Screening microsatellite markers associated with alkaline tolerance in Leuciscus waleckii

Saline-alkaline water use has broadened the development of Chinese fisheries. Breeding new varieties of alkaline-resistant fish is a fundamental task, and elucidating fish alkaline-resistant mechanisms, identifying candidate genes, and exploring their functions are crucial.Decoding genome information promotes the use of molecular markers and selection of candidate genes. <i>L</i><i>euciscus waleckii</i> (Dybowski) is highly tolerant to high salinity and alkalinity and survives in Dali Lake (Inner Mongolia) with alkalinity up to 53.57 mmol/L (pH 9.6). Therefore, this fish species is a good subject to investigate the evolutionary mechanism of high salinity and alkalinity adaptation. <i>L. waleckii</i> in Dali Lake differ from their freshwater counterparts because they are characterized by a breeding migration in which they spawn in freshwater and grow in alkaline water. Marked differences are observed during acute-phase alkaline tolerance between the alkaline population from Dali Lake and the freshwater population from the Songhuajiang River, indicating the genetic heritability of alkaline tolerance. However, the mechanism of high tolerance to alkalinity remains unknown, and very few physiological and genetic studies have been performed. Thus, we prepared a hybrid F₂ system (alkaline Dali <i>Leuciscus</i> &#215; freshwater Songhua <i>Leuciscus</i>). A large number of candidate genes are associated with alkaline-resistance traits, and microsatellites, single nucleotide polymorphisms, and other molecular markers have been applied in fish population genetics studies. We used the gene recombination principle to select molecular markers closely related to alkaline-resistance traits and located functional genes using molecular markers. In this study, we examined and genotyped alkaline tolerance in 77 hybrid F₂ individuals using 39 simple sequence repeat (SSR) markers, including 19 expressed sequence tag EST-SSRs. The individuals were divided into three groups of 43, 20, and 14 individuals based on their alkaline tolerance. Fisher''s exact probability test was used to examine the associations between markers and the trait. The results showed that two markers were strongly linked to alkaline tolerance (<i>P</i><0.05), and one was an EST-SSR. Sequence alignment of that EST-SSR showed that it was highly homologous with the hypoxia inducible factor <i>HIF-3</i><i>a </i>gene of Wuchang bream (<i>Megalobrama amblycephala</i>) and the <i>HIF-4</i><i>a</i> gene of grass carp (<i>Ctenopharyngodon idellus</i>). These genes are involved in the response to hypoxia and increased hypoxia tolerance in fish. The approach was to select a functional gene using molecular markers, localize the functional gene, and narrow the range of candidate genes to lay the foundation for breeding new varieties of alkaline-resistant fish. In-depth study of this functional gene will be conducted in the future. Our results suggest further analyses of candidate alkaline-responsive genes, which will help in the understanding of teleost adaptation under extreme environmental stress and ultimately benefit future breeding for an alkaline-tolerant fish strain.