• 中文核心期刊
  • CSCD来源期刊
  • 中国科技核心期刊
  • CA、CABI、ZR收录期刊

OsVHA-A1基因缺失突变水稻早衰生理过程研究

Physiological Process and Mechanism of Senescence in Mutant Rice with Functional Deletion on OsVHA-A1 Gene

  • 摘要: 负责编码水稻液泡膜ATP酶A亚基的OsVHA-A1基因在水稻生长发育和抵抗环境压力等诸多方面发挥重要作用。本试验以筛选纯合的OsVHA-A1基因缺失突变体株系及其野生型为材料,发现OsVHA-A1基因缺失突变会导致该突变体水稻生育后期发生严重的早衰现象与减产。两种基因型水稻叶片与根系中抗氧化保护酶活性随生育期呈现动态变化,孕穗期后突变体根系和叶片的衰老指标(包括H2O2含量、O2-产生率和MDA含量)均明显高于野生型;与野生型对比,突变体根系衰老程度显著高于其叶片。在早衰前后两个时期,即苗期和灌浆高峰期,对OsVHA-A1基因进行qRT-PCR定量,发现灌浆高峰期时的突变体与野生型叶片和根系中的OsVHA-A1基因相对于苗期均下调表达,V-ATPase酶活性也显著下降,突变体下降幅度大于野生型。利用16S扩增子分析根际土壤微生物组成时发现,灌浆高峰期突变体根际土壤中植物病原菌的含量显著上升。同时,HPLC技术测得突变体根际土壤中对羟基苯甲酸和对香豆酸两种酚酸类物质极显著低于野生型。说明不同基因型水稻根际土壤微生物存在对根系分泌物的选择性利用并诱导根际病原菌的增长。相关性分析结果表明,孕穗期后两种基因型水稻的根系活力下降变化与其功能叶片叶绿素含量及光合速率降低呈一定的相关关系。综上所述,OsVHA-A1基因缺失突变直接介导了水稻根系和叶片早衰的发生,并通过选择性诱导根际病原菌增长而加剧突变体根系与整体老化。

     

    Abstract: Vacuolar H+-ATPases (V-ATPase) is a multi-subunit enzyme complex found in the tonoplast of eukaryotes. V-ATPase subunitA(VHA) encoded by OsVHA-A1 gene is crucial in the development and tolerance to environmental stress of rice. This study applied a wild type and a purified mutant rice with a single cytosine deletion from its OsVHA-A1 gene to compare the differences of their phenotypes during the entire growth period. The mutant rice senesced at late-growth stage resulting a significant yield reduction as compared to the wild type. The activities of antioxidant enzymes including SOD, POD and CAT of the two isogene rice lines showed differential temporal patterns.The senescence-induced increases on O2- production as well as H2O2 and MDA contents in the leaves and roots of the mutant rice after booting stage were generally higher than those of the wild type.The performance of the roots tended to be poorer than that of the leaves in the mutant type in comparison with that of the wild type. OsVHA-A1 was significantly down-regulated and the V-ATPase activity significantly declined at grain-filling stage after senescence from seeding stage before senescence for both lines. But the down-regulated OsVHA-A1 expression and reduced V-ATPase activity in the roots and leaves were greater in the mutant rice than those in the wild type. It appeared that OsVHA-A1 played a crucial role in regulating rice senescence.Aside from genetic changes, environmental factors also contributed to the heightened root senescence, as the 16S rDNA sequencing showed that the pathogenic fungi population in the rhizosphere soil increased significantly when the mutant type at its grain-filling stage. In the soil, HPLC analysis identified 5 phenolic acids, i.e., phydroxybenzoic, vanillin, syringate, pcoumaric acid, and ferulic acid. The contents of phydroxybenzoic and pcoumaric acid were extremely significantly lower associated with the mutant than the wild type. It suggested that the pathogens might participate in the process of root senescence. Furthermore, the declined root activity was found correlating with the chlorophyll or photosynthesis decrease in the isogen rice lines after booting stage.It was concluded that the absence of functional OsVHA-A1 directly affected the senescence, whereas the altered underground microbial community further hastened the aging process of the rice plant.

     

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