甜瓜无毛基因gl的精细定位和转录组分析

Trichomes on plants play important roles in plant survival and development. The glabrous melon plant can reduce the residual pesticides and enhance the resistance to some injurious insects. Therefore, fine mapping and transcriptome analysis for the glabrous trait in melon will not only be helpful in marker-assisted selection (MAS) for the smooth plant in molecular breeding, but also help us to understand the molecular mechanism of the multicellular trichome development. We identified a glabrous material in melon which exhibited a completely glabrous phenotype on leaves, stems, flowers, sepals, and fruits. Genetic analysis indicated that the glabrous phenotype in melon was inherited as a single recessive gene which was named gl. Based on our previous study, we will develop two F2 population by crossing glabrous material M68 with two normal melon inbred lines DHL92 and TopMark, respectively. The BSA (Bulked Segregation Analysis) method will be used for primary mapping of gl gene using SSR markers developed from melon genome DHL92. Furthermore, the glabrous material M68 will be resequenced and compared with reference genome DHL92 and TopMark by in silico PCR and sequence mapping to develop SSR, SNP or Indel marker in the candidate region harboring gl gene. Then these new polymorphism markers will be used to genotype in large F2 mapping population for fine mapping gl gene in 50-100 kb region, and the candidate genes in this target region will be predicted and annotated. In addition, the transcriptome analysis will be carried out to compare the differentially expressed genes (DEGs) between glabrous line M68 and normal inbred line DHL92. This will not only help us for final cloning and better understand the genetic regulation of gl gene in melon, but also provide gene resource and theoretical basis for molecular breeding of glabrous lines in melon.

无毛甜瓜材料不仅可以减少农药残留，同时可以增强对部分害虫的抗性，开展甜瓜无毛性状研究，对甜瓜基础研究和分子育种具有重要的理论和实践意义。在前期研究中，我们发些一个甜瓜无毛材料，遗传分析表明该性状由一个隐形单基因（gl）控制。本项目拟以甜瓜无毛材料M68与正常有毛材料DHL92和TopMark构建两个F2作图群体，利用BSA法和小群体对该性状进行初步定位；然后将无毛材料M68进行重测序和从头组装，通过与另外两个亲本基因组序列的比对，在无毛基因的候选区域开发SSR、SNP和Indel等标记，同时进一步扩大作图群体对gl基因进行精细定位，并对候选区段进行基因预测和功能分析；此外，我们还将通过正常甜瓜材料与无毛材料在幼叶期的转录组比较及对差异表达基因的功能注释和分类，解析甜瓜表皮毛形成发育的基因调控网络，确定甜瓜gl基因的候选基因，为最终克隆甜瓜gl基因及揭示多细胞表皮毛发育的分子机理奠定基础。

表皮毛覆盖在植物植株表面，由细胞表皮分化而成，可保护植株减少虫害和病原体的侵害。拟南芥单细胞毛状体起始发育的调控途径已经研究的非常清楚，而对甜瓜多细胞毛状体的起始和发育的研究却很少。.本项目组发现一个在整个生育期稳定无毛的甜瓜突变体材料，遗传分析发现，该无毛性状是由一对隐性单基因控制，命名为gl基因。本项目通过构建作图群体和亲本重测序，将gl基因定位于甜瓜第8染色体上约11.58kb的范围内，进一步根据亲本序列差异分析和表达分析比较，确定了gl基因的候选基因为一个编码含有721个氨基酸的HD-ZIP IV 转录因子，为后续深入研究该基因的功能奠定了基础。进一步根据候选基因在两亲本间的序列差异，开发了一个与gl基因共分离的dCAPS标记，可以在自然群体中准确的鉴别出杂合基因型和纯合基因型，因此该标记可用于分子标记辅助选择，将会显著提高育种效率。本项目还对有毛材料和无毛材料进行了转录组分析，在两个混池之间共找到差异表达基因2368个，其中上调基因1195个，下调基因1173个。并对这些差异表达基因进行了GO和KEGG功能分析，这些结果不但为进一步深入研究甜瓜表皮毛形成的分子机制提供了扎实的基础，而且有助于丰富和完善对多细胞类型表皮毛形成分子机制的研究。