小麦旗叶宽相关基因TaNAL1-5的克隆与功能分析

Cloning and Functional Analysis of Flag Leaf Width-Related Gene TaNAL1-5 in Common Wheat(Triticum aestivum L.)

叶片是植物进行光合作用的主要器官,与植物形态建成有重要关系。旗叶的大小及其与茎杆的夹角直接影响到小麦植株的受光,从而影响到小麦的产量水平。本研究利用比较基因组学的方法,以水稻重要叶宽基因Os NAL1为参考序列在小麦中克隆其同源基因TaNAL1-5,挖掘其优良等位变异并研究其对旗叶宽等重要农艺性状的影响。结果表明,小麦TaNAL1-5A、TaNAL1-5B和TaNAL1-5D基因均由5个外显子和4个内含子组成,TaNAL1-5A和TaNAL1-5B编码600个氨基酸,TaNAL1-5D编码598个氨基酸,具有典型的半胱氨酸/丝氨酸胰蛋白酶结构域。系统进化树分析发现小麦TaNAL1-5基因与乌拉尔图小麦、粗山羊草、二穗短柄草等单子叶植物亲缘关系较近,而与拟南芥、大豆等双子叶植物亲缘关系较远。在不同小麦品种中,TaNAL1-5B/5D没有检测到序列多态性,而TaNAL1-5A呈现单体型的9个SNP位点和一个19 bp Indel的两种等位变异,并根据19 bp的Indel设计了TaNAL1-5A两种等位变异的功能标记。功能标记扫描发现,TaNAL1-5A与小麦旗叶宽度、千粒重、小穗数呈极显著正相关。此外,基因表达分析显示TaNAL1-5基因在籽粒、根、茎、叶、穗、穗下节等部位均表达,且在开花后25天即灌浆高峰期表达量最高,可能参与了籽粒的形成过程。本研究有助于解析小麦旗叶形成的遗传控制及株型改良。

Leaf is the main organ of photosynthesis in plants, playing a vital role in morphology development. The size of flag leaf and the angle between the flag leaf and stem have a great effect on the light reception, and the yield potential is mainly determined by the photosynthetic characteristics of flag leaf. In this study, using comparative genomics method, we cloned TaNALI-5 genes in common wheat, homologous to OsNAL1, an important leaf width gene in rice. The allelic variants of TaNAL1-5 and their effects on flag leaf width and other agronomic traits were also investigated. The data showed that TaNAL1-5A, TaNAL1-5B and TaNAL1-5D gene were composed of five exons and four introns. Both TaNAL1-5A and TaNAL1-5B contained 600 amino acids, and TaNAL1-5D did 598 amino acids with typical cysteine/serine trypsin domain. Phylogenetic tree analysis revealed that TaNAL1-5 genes had closer genetic relationship with NAL1 genes from monocots, e.g.T, urartu, Aegilops tauschii, Brachypodiurn distachyon than those from dicotyledonous plants, such as Arabidopsis and soybean. In differentwheat varieties, no sequence polymorphisms were detected in TaNAL1-5B/5D, while two haplotypes, Hap-A 1 and Hap-A 2 were characterized in TaNA L1-5A for nine SNPs and a 19 bp Indel were present in its two alleles. Based on the 19 bp Indel, a molecular marker was developed to identify Hap-A 1 and Hap-A2. Using a natural population, TaNAL1-5A was found highly significant correlated with flag leaf width, grain weight and spikelet number. In addition, expression analysis provided that TaNAL1-5 was expressed in developing seeds, root, stem, leaf, panicle and peduncle, and had a highest expression level on the developing seeds at 25 days-affer-anthesis, implying the involvement of TaNAL1-5 on seed development. Our study provides assistance for genetic control and plant type improvement on flag leaf formation in common wheat.