一氧化氮参与低钾调控烟草根系生长的机制

A third of cultivated land is low potassium (K) or serious lack of K in china. Excavation of K absorption capacity of tobacco roots will provide theoretical and material foundation for K utilization efficiency. Previous studies show that K plays a very important role in root growth of tobacco. However, the mechanism of K regulation on root system formation were unclear. Related studies had shown that nitric oxide (NO) was involved in regulation of many aspects of root growth and development, and the mechanism of NO involved in root growth under K starvation in tobacco were unclear. In an attempt to get a better understanding of NO involved in regulation of root growth under low K, we tried to further analysis the response of root growth on the different genotypes tobacco with tolerance to low-K Stress, the response of NO and reactive oxygen species (ROS) of root with exogenous NO and NO scavenger, and discover the mechanism of NO involved in root growth under different levels of K in tobacco at first; Secondly, The effect of different K levels on key enzymes activity and expression of relevant genes in NO biosynthetic pathway was studied. At last，preliminary study on expression of auxin (IAA) transpoter, 3[H]IAA transport and the distribution of IAA in roots was visualized by DR5::GUS, We also examined the effects of exogenous auxin (NAA) and a transport inhibitor (NPA) on expression of relevant genes in NO biosynthetic pathway，and the content of NO in root was studied by NO fluorescent probe. All these results will clarify the regulation mechanism of NO involved in root growth under K starvation in tobacco.

我国现有耕地约1/3土壤出现缺钾(K)，发掘植物根系对K吸收的潜力对提高K肥利用率具有重要意义。相关研究表明一氧化氮(NO)参与调控植物根系生长，而NO是否参与低K调控植物根系生长并不清楚。本项目以不同K基因型烟草品种为试材，首先，研究低K胁迫下烟草根系构型及内源NO和活性氧(ROS)的响应，揭示NO参与低K调控根系生长的机制；其次，研究低K胁迫下NO合成途径关键酶及合成基因NtNOA1、NtNIA1和NtNIA2的表达差异；最后，利用DR5::GUS转基因材料研究施用NO供体和清除剂处理下，对内源生长素(IAA)、3[H]IAA极性运输及主要运输蛋白PIN家族的表达差异；同时，利用NO特定荧光探针定位研究施用外源生长素(NAA)和极性运输抑制剂(NPA)，对内源NO及相关合成基因的调控，阐明NO与IAA在低K调控根系生长中的互作机制，从生理和分子水平揭示NO在低K调控烟草根系生长的机制。

我国现有耕地约1/3土壤出现缺钾(K)，发掘植物根系对K吸收的潜力对提高K肥利用率具有重要意义。相关研究表明一氧化氮(NO)参与调控植物根系生长，而NO是否参与低K调控植物根 系生长并不清楚。本项目以不同K基因型烟草品种为试材，首先，研究低K胁迫下烟草根系构型 及内源NO和活性氧(ROS)的响应，揭示NO参与低K调控根系生长的机制；其次，研究低K胁迫下N O合成途径关键酶及合成基因NtNOA1、NtNIA1和NtNIA2的表达差异；最后，利用DR5::GUS转基 因材料研究施用NO供体和清除剂处理下，对内源生长素(IAA)、3[H]IAA极性运输及主要运输蛋 白PIN家族的表达差异；同时，利用NO特定荧光探针定位研究施用外源生长素(NAA)和极性运输 抑制剂(NPA)，对内源NO及相关合成基因的调控，阐明NO与IAA在低K调控根系生长中的互作机 制，从生理和分子水平揭示NO在低K调控烟草根系生长的机制。.结果表明，NO参与了植物根系的形态建成，在前期低钾诱导NO的产生是通过NR途径发生的，后期是通过NOS途径发生的；采用药理学手段进行温室条件下的水培实验和实验室琼脂培养基实验，在低钾营养条件下添加cPTIO，L-NAME，Tu使得烟草一级侧根显著增长，这说明增加NO确实能够参与低钾胁迫下的烟草根系的伸长。两个耐钾能力差异大的烟草品种在低钾胁迫条件下生长差异显著。不耐钾的烟草品种的根系生长显著被抑制，其原因主要是因为一级侧根的伸长和发生被抑制。不耐钾烟草品种根系NO积累量显著增加，且调控了低钾胁迫下根系的伸长。