小麦TaGW2-6A等位变异系细胞分裂素和淀粉合成相关基因表达分析

发布时间：2018-03-27 14:55

本文选题：小麦　切入点：籽粒发育　出处：《西北农林科技大学》2017年硕士论文

【摘要】：由于人口的不断增加和可耕地的减少,粮食短缺已成为最严重的全球问题之一。作为小麦产量的重要组成因子,粒重是人们近年来研究的热点。目前在小麦中已经成功克隆了粒重基因TaGW2-6A,而其“T”碱基插入突变能够显著增加小麦的粒宽和粒重。本研究以CS及其近等基因系NIL31为材料,从细胞学水平、籽粒灌浆以及籽粒细胞分裂素和淀粉合成相关基因的表达等方面深入探讨TaGW2-6A不同等位变异对籽粒发育的影响。主要研究结果如下:1.小麦籽粒灌浆速率、干物质积累速率与粒重紧密相关。从花后9天起,NIL31的籽粒胚乳鲜重和干重显著高于CS,在花后35天时达到最大值,分别提高了46.04%和48.71%。同时,NIL31的灌浆速率也显著高于CS,特别是花后9-20天。与CS相比,NIL31籽粒粒宽、粒厚和粒长分别增加了约20%,13.6%和12.9%,千粒重增加了约47.9%。这些结果表明,TaGW2-6A等位变异可能通过影响籽粒灌浆及干物质积累速率进而控制籽粒的大小。2.随着胚乳的发育,CS和NIL31的中央胚乳细胞的长度和宽度从花后3-25天逐渐增加,但NIL31的细胞比CS显著增大,特别是在花后9-15天。同时,NIL31的细胞增殖速率也显著高于CS。另外,CS的种皮比NIL31厚且致密,其可能限制了胚乳细胞的生长,限制了库的扩大。因此,我们推测TaGW2-6A等位变异可能通过胚乳的增殖及表皮细胞的结构,最终影响种子的大小。3.细胞分裂素合成基因和细胞分裂素降解基因能够促进细胞分裂素的积累,进而影响细胞的分裂。qRT-PCR结果表明,NIL31中细胞分裂素合成基因TaIPT2,TaIPT3,TaIPT5和TaIPT8的表达模式与CS相似,但各基因的转录水平明显高于CS。与TaIPTs相反,细胞分裂素降解基因TaCKX1,TaCKX2和TaCKX6的转录水平在CS中显著高于NIL31。因此,我们NIL31中由于细胞分裂素合成基因的高表达及细胞分裂素降解基因的低表达,进而导致细胞分裂素的积累,促进籽粒细胞数目的增多、体积增大和籽粒灌浆速率的提高,最终导致大籽粒的形成。4.淀粉的合成直接影响小麦籽粒灌浆,其合成受负调控因子SPA和TaRSR1及淀粉合成基因TaAGPL和TaAGPS的调节。花后6天到15天,淀粉合成酶基因TaAGPL和TaAGPS在NIL31中的转录水平显著高于CS。SPA和TaRSR1在CS中高表达,而在NIL31中低表达。因此,TaGW2-6A等位变异通过影响淀粉合成相关基因的表达,进而促进NIL31中淀粉的合成和积累,最终也影响籽粒的大小。综上所述,TaGW2-6A等位变异可能通过泛素蛋白酶体途径调控细胞分裂素和淀粉合成相关基因的表达,进而促进胚乳细胞的分裂和淀粉的积累造成大籽粒的形成。
[Abstract]:As a result of increasing population and decreasing arable land, food shortages have become one of the most serious global problems. The grain weight gene TaGW2-6A has been successfully cloned in wheat, and its "T" base insertion mutation can significantly increase the grain width and grain weight of wheat. In this study, CS and its near-isogenic line NIL31 were used as materials. The effects of allelic variation of TaGW2-6A on grain development were studied in terms of cytological level, grain filling and expression of genes related to cytokinin and starch synthesis. The main results were as follows: 1. Grain filling rate of wheat. Dry matter accumulation rate was closely related to grain weight. The fresh and dry weight of endosperm of NIL31 was significantly higher than that of CSS from 9 days after anthesis, and reached the maximum at 35 days after anthesis. The grain filling rate of NIL31 was significantly higher than that of CSs, especially 9 to 20 days after anthesis. The grain width of NIL31 was higher than that of CS. The grain thickness and grain length increased by about 13.6% and 12.9%, respectively, and the 1000-grain weight increased by about 47.9%. These results indicate that the allelic variation of TaGW2-6A may control grain size by affecting grain filling and dry matter accumulation rate. The length and width of central endosperm cells in NIL31 increased from 3 to 25 days after anthesis. However, the cell proliferation rate of NIL31 was significantly higher than that of CS, especially at 9-15 days after anthesis. In addition, the seed coat of CS was thicker and denser than that of NIL31, which may limit the growth of endosperm cells and the enlargement of library. We speculate that TaGW2-6A allelic variation may affect seed size by endosperm proliferation and epidermal cell structure. Cytokinin synthesis gene and cytokinin degradation gene can promote cytokinin accumulation. Furthermore, the results of QRT-PCR showed that the expression patterns of cytokinin synthesis gene TaIPT2, TaIPT3, TaIPT5 and TaIPT8 were similar to those of CS, but the transcriptional level of these genes was significantly higher than that of TaIPTs. The transcription levels of cytokinin degrading gene TaCKX1, TaCKX2 and TaCKX6 were significantly higher in CS than in NIL31.Therefore, the high expression of cytokinin synthesis gene and the low expression of cytokinin degrading gene in our NIL31 resulted in the accumulation of cytokinin. The increase of the number of grain cells, the increase of grain volume and the increase of grain filling rate resulted in the formation of large grains. 4. Starch synthesis directly affected grain filling in wheat. Its synthesis was regulated by the negative regulatory factors SPA and TaRSR1 and the starch synthase genes TaAGPL and TaAGPS. From 6 to 15 days after anthesis, the transcription levels of TaAGPL and TaAGPS in NIL31 were significantly higher than those of CS.SPA and TaRSR1 in CS. Therefore, the allelic variation of TaGW2-6A affects the expression of genes associated with starch synthesis, and thus promotes the synthesis and accumulation of starch in NIL31. In conclusion, the allelic variation of TaGW2-6A may regulate the expression of cytokinin and starch synthase related genes through the ubiquitin proteasome pathway. Thus, the division of endosperm cells and the accumulation of starch resulted in the formation of large grains.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S512.1

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