水稻转录因子OsMADS57参与硝酸盐调控根系伸长的机制

项目名称： 水稻转录因子OsMADS57参与硝酸盐调控根系伸长的机制

项目编号： No.31471936

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 农业科学

项目作者： 张亚丽

作者单位： 南京农业大学

项目金额： 95万元

中文摘要： 理想的根系性状是水稻高效吸收养分的基础，根系发育和土壤氮供应关系密切。强烈的根际硝化作用使水稻根系处于铵、低浓度硝酸盐营养中。目前硝酸盐调控根系生长的研究集中在旱地作物，而硝酸盐调控水稻根系生长的分子机制近乎空白。我们发现水稻MIKC型MADS-box转录因子MADS57的表达受硝酸盐水平调控，低浓度硝酸盐增强其表达。低硝水平下mads57突变体根系伸长被抑制，其机制并不清楚。以MADS57基因突变体和超表达材料为试材，研究不同氮处理下MADS57表达模式及根系响应，从细胞水平探讨其根系伸长变化原因；研究硝酸盐高亲和转运体基因表达，探明它们是否参与依赖于MADS57的低浓度硝酸盐调控水稻根系伸长；采用pDR5::GFP等转基因材料，研究独角金内酯、生长素及相关基因变化，揭示独角金内酯和生长素与MADS57调控根系伸长的关系，从生理和分子角度阐明MADS57参与硝酸盐调控水稻根系伸长的机制。

中文关键词： 水稻；OsMADS57；硝酸盐；根系；伸长

英文摘要： Ideotype root architecture is important for efficient N acquisition in plant. The plant root system is extremely sensitive to variations in nitrogen form and availability in the soil. Rice plants have aerenchymatous tissue in their roots that allow partial oxygen to release into the soil. Thus nitrification occurs immediately in the aerobic niche of the rhizosphere or on the surface of the roots. Therefore, even in a flooded paddy soil, rice roots are actually exposed to the mixture of NH4+ and low NO3- concentration. Numerous experiments showed molecular mechanism for nitrate regulating root growth especial for lateral root proliferation in Arabiopsis. However, mechanism for nitrate regulating rice root growth is poorly understood, mainly due to ignoring nitrate nutrition in rice plant. The Arabidopsis ANR1 gene, which encodes a NO3- -inducible and root-specific member of the MADS-box family of transcription factors, was identified as a key component of the signal transduction pathway by which NO3- stimulates lateral root proliferation. The OsMADS57 MADS-box gene is one of the analogue genes for AtANR1. Our preliminary study showed that under 0.2 mM NO3- supply, Osmads57-TDNA mutants exhibited repressed the elongation of seminal and adventitious root, compared with wild type (WT). However, no difference was observed between mutants and WT under 5 mM NO3- and 0.2 mM NH4+ supplies. What role might OsMADS57 play in converting low NO3- stimulus at the root tip into an increased rate of elongation? First, Expression pattern in response to nitrogen availability and forms, and tissue localization analysis of OsMADS57 are used to verify its molecular function. To gain insight into how root elongation responds to low nitrate supply, root elongation was followed morphologically using the CYCB1.1::GUS marker for G2/M phase cells. It is reasonable to predict that root phenotype in mutant is due to the absence of the positive factors response to low nitrate concentration. One possibility is suggested by high affinity NO3--uptake systems including NRT2 homologs and their partner protein NAR2 homologs, whose expression will be analyzed in mutants and WT under N treatments to verify their role in modulating the rate of primary root elongation through OsMADS57. Strigolactones have been verified to play an important role in root elongation regulated by low nitrate condition. And auxin is key hormonal signals that control the cellular architecture of the primary root. Strigolactones' secretion and D genes and auxin distribution and related auxin transporters are analyzed to test strigolactones and auxin participating root elongation regulated by NO3-.

英文关键词： Rice;OsMADS57;Nitrate;Root;Elongation