mGWAS解析甲醇-茉莉素代谢级联调控水稻叶片衰老的研究

发布时间：2018-05-05 10:46

本文选题：水稻 + 衰老　；参考：《华中农业大学》2017年博士论文

【摘要】：衰老作为多细胞生物生命周期的最终环节,一直备受关注。叶片衰老是植物生长发育的重要阶段,伴随着氮元素等有益离子从衰老的叶片中向幼叶等源组织以及种子等库组织中转运并重新利用,对种子萌发、作物产量和品质均有重要影响。同时,叶片衰老也是植物适应环境的重要手段。水稻叶片的自然衰老是从授粉开始的,由于水稻种质资源抽穗期上的巨大差异,直接以叶片衰老为靶性状进行全基因组关联分析(GWAS)以克隆控制衰老的基因是十分困难的。茉莉素是被广泛报道参与叶片衰老调控的重要代谢物,通过茉莉素含量的代谢组学全基因组关联分析(mGWAS)或许能辅助克隆控制衰老的关键基因。本研究以221份水稻种质资源为材料,测定了叶片中10种茉莉素的含量,发现了具有生物学活性的几种茉莉素在籼稻品种叶片中的含量显著高于粳稻。进一步的mGWAS预测到13个位点可能调控茉莉素含量的自然变异。通过对其中最显著的两个位点的分析,我们推测编码果胶甲基酯酶的OsPME1和编码果胶甲基转移酶的OsTSD2两个基因可能调控茉莉素含量。通过检测转基因和突变体中茉莉素含量,我们鉴定了OsPME1和OsTSD2正调控水稻叶片中茉莉素积累的功能。通过在30个水稻品种中检测表达量,我们发现籼稻中OsPME1的表达量显著高于粳稻中,提示OsPME1表达量的变异可能影响茉莉素含量的自然变异。通过进一步田间表型的考察鉴定了OsTSD2突变导致水稻叶片衰老的延迟,OsPME1的转基因材料也出现了黑暗诱导的叶片衰老异常的表型。此外,外源添加Me-JA能够回复tsd2突变体叶片衰老延迟的表型,这说明tsd2突变体延迟衰老至少部分原因是茉莉素含量的降低。OsPME1和OsTSD2在生化和代谢途径上并不与茉莉素合成相关,最直接的功能分别是细胞壁果胶去甲基化和甲基化,甲基化的果胶是植物甲醇的主要来源,因此我们推测OsPME1和OsTSD2通过调控由细胞壁果胶去甲基化产生的甲醇影响茉莉素合成。我们首先通过转基因的方法验证了PME家族的另一个基因OsPME11和PME抑制子家族(PMEI)的一个基因OsPMEI-1都能影响茉莉素合成相关基因的表达,这说明影响细胞壁果胶甲基化程度的基因都能影响茉莉素合成途径。进一步向水培培养的水稻外源添加甲醇发现,茉莉素合成途径相关基因的表达受到甲醇的强烈影响,随着甲醇的添加茉莉素含量也显著提高。综上所述,我们鉴定了甲醇-茉莉素代谢级联在促进水稻叶片衰老中的作用。
[Abstract]:Aging, as the final link of multicellular life cycle, has been paid more and more attention. Leaf senescence is an important stage of plant growth and development. With the transfer and reuse of beneficial ions such as nitrogen from the senescent leaves to the young leaves and so on, the seeds germinate. Crop yield and quality have important effects. At the same time, leaf senescence is also an important means for plants to adapt to the environment. The natural senescence of rice leaves begins with pollination. Because of the great difference in heading date of rice germplasm resources, it is very difficult to clone the genes that control senescence by using leaf senescence as the target trait of the whole genome association analysis (GWAS). Jasmine is an important metabolite involved in the regulation of leaf senescence, and it may be helpful to clone the key genes to control senescence by the whole genome association analysis of the content of jasmine. In this study, 221 rice germplasm resources were used to determine the contents of 10 kinds of jasmine in leaves, and it was found that the contents of several kinds of jasmine with biological activity in the leaves of indica rice varieties were significantly higher than those in japonica rice varieties. Further mGWAS predicted that 13 loci might regulate natural variation of jasmine content. Based on the analysis of the most significant two loci, we speculated that the OsPME1 encoding pectin methyl esterase and the OsTSD2 encoding pectin methyltransferase might regulate the content of jasmine. By detecting the content of jasmonin in transgenic and mutant, we identified the function of OsPME1 and OsTSD2 in regulating the accumulation of jasmonin in rice leaves. By detecting the expression of OsPME1 in 30 rice varieties, we found that the expression of OsPME1 in indica rice was significantly higher than that in japonica rice, suggesting that the variation of OsPME1 expression might affect the natural variation of jasmine content. Through further field phenotypic investigation, the transgenic materials with OsTSD2 mutation causing delayed senescence of rice leaves also showed dark induced abnormal phenotypes of leaf senescence. In addition, exogenous addition of Me-JA could restore the delayed senescence phenotype of tsd2 mutants, which indicated that the delayed senescence of tsd2 mutants was at least partly due to the decrease of jasmine content. OsPME1 and OsTSD2 were not related to the biochemical and metabolic pathways of jasmine synthesis. The most direct function is cell wall pectin demethylation and methylation, and methylated pectin is the main source of plant methanol. Therefore, we speculate that OsPME1 and OsTSD2 affect jasmine synthesis by regulating methanol produced by cell wall pectin demethylation. We first demonstrated by transgenic methods that another gene of the PME family, OsPME11, and a gene of the PME suppressor family, OsPMEI-1, could affect the expression of genes associated with jasmine biosynthesis. These results suggest that the genes that affect the degree of pectin methylation in cell wall can affect the biosynthesis of jasmine. It was found that the expression of genes related to jasmine biosynthesis pathway was strongly affected by methanol, and the content of jasmine increased significantly with the addition of methanol. In conclusion, we identified the role of methanol-Jasmine metabolic cascade in promoting senescence in rice leaves.
【学位授予单位】：华中农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S511

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