罗非鱼体色突变体的遗传解析

Fishes display very rich body color and dazzling pigment pattern. The body color on fish species is crucial for their survival, breeding, avoiding predators, preventing ultraviolet erosion, and so on. Recently, we found that the body color of gata2a mutants in Nile tilapia became deep black due to increased number of melanophores, and with significant up-regulation of mitfa expression, while mutation of mitfa resulted in shallower body color due to decreased number of melanophores. Additionally, two Gata2a binding sites were detected in the promoter of mitfa by sequence analysis. In red tilapia, without any melanophores, the expression of mitfa was significantly down-regulated. Cross-breeding and RAD sequencing of the parents and 100 F2 fish indicated that the red color is controlled by an autosomal dominant gene R. Based on these results, we propose that both gata2a and R gene are important genes which can control the development of melanophores by repressing the expression of mitfa. This project aims to elucidate the relationship of three genes by conducting the following researches, 1) Effects of gata2a mutation on body color and the mechanism involved in; 2) Effects of mitfa mutation on body color and the mechanism involved in; 3) The transcriptional regulation of mitfa by Gata2a; 4) Genetic bases for the absence of melanophores in red tilapia. This study will help to reveal the molecular mechanism and regulatory network of fish body color formation, and also provide a reference for the cultivation of the new strains of tilapia.

鱼类具有非常丰富的体色和令人眼花缭乱的色素斑图。体色对其生存繁衍、躲避敌害和防止紫外侵蚀等均具有十分重要的意义。最近，我们发现尼罗罗非鱼gata2a突变体黑色素细胞增多，体色呈深黑色，mitfa表达显著上调，在mitfa启动子有gata2a结合位点。野生鱼突变mitfa则体色变浅，黑色素细胞大量减少。而红罗非鱼基本没有黑色素细胞，mitfa表达显著下调，杂交建系和RAD测序表明红色由显性基因R调控。基于此，我们提出gata2a和红罗非鱼的R基因是控制黑色素细胞发育的关键基因，能抑制mitfa的表达，从而控制黑色素细胞分化的假说。本项目拟开展1）gata2a突变对罗非鱼体色的影响及机制解析；2）mitfa突变对体色的影响及机制解析；3）gata2a对mitfa的转录调控；4）红罗非鱼黑色素细胞缺失的遗传解析。本研究有助于揭示鱼类体色形成的分子机制及调控网络，也为罗非鱼体色新品系培育提供参考。

体色是一种重要的经济性状，决定着水产动物的生产实用性。罗非鱼是世界性养殖鱼类。中国是罗非鱼最大生产国和出口国，其中红罗非鱼更是因其体色鲜红而深受消费者喜爱。但至今未找到决定红色形成的主效基因。本研究通过多组学分析和QTL定位图位克隆了红色主效基因R，利用基因编辑创制了mitfa、mitfb、gata2a、tyrb、pmela、pmelb、hps4、csf1ra、pax7、R等单突变模型，以及mitfa;mitfb、pmela;pmelb双突变模型，并进行了遗传解析。主要进展如下：1）突变gata2a并获得深黑色罗非鱼，发现gata2a突变致眼睛发育异常，由此间接导致体色黑化；2）通过mitfa;mitfb双突变，创制出可用于水产养殖的红黄色罗非鱼，首次发现mitf可能调控红/黄色素细胞的数量和大小；3）通过基因组测序和重测序、转录组测序及QTL定位筛选出一个红色候选基因R，并利用基因编辑进行功能验证；4）结合MAS-GMT技术和基因编辑创制出遗传全雄无黑斑红罗非鱼；5）通过突变黄色素细胞分化基因csf1ra，创制出灰色及灰色黑尾的罗非鱼；6）开展了体色基因大规模编辑，创制出金色、银色、红黄色、红色、透明红等多种罗非鱼突变体并开展了遗传解析。本研究中获得的具有不同体色的突变体不仅使罗非鱼成为体色研究的重要模型，而且为水产养殖提供了新种质。目前在Aquaculture、Aquaculture Reports、International Journal of Molecular Sciences和The Journal of Heredity等杂志发表论文16篇。作学术报告5人次，其中特邀报告3人次。培养博士后2人，博士生3人，硕士生4人。