低氮诱导小麦主根伸长的分子机理研究

A plant's root system is of vital importance in acquiring nutrients from the soil. Root system architecture (RSA), the spatial configuration of a root system in the soil, is influenced by numerous biotic and abiotic factors including nutrient status. It has been proved that low nitrogen stress can induce root elongation in wheat, however, we know very little about the molecular mechanism of it. The ideal materials, a pair of near isogenic lines(178A and 178B,the responses of their primary roots to low nitrogen stress showed significant differences), were used in this study to probe into the molecular mechanism of wheat primary root elongation induced by low nitrogen stress. The content of this project includes the following components:(1)To screen the differentially expressed genes in the primary root tips of the NILs under control and low nitrogen stress conditions using qPCR; (2)To analysis the functions of the differentially expressed genes by overexpressing those genes in Arabidopsis and ascertain the corresponding pathways of those genes; (3)To further analysis the functions of candidate genes by overexpressing and underexpressing those genes in wheat(178A and 178B); (4)To measure the expression levels of those genes in corresponding pathways. This research may lead to a prelimary understanding of the molecular mechanism of wheat primary root elongation induced by low nitrogen stress and provide useful information for genetic improvement of wheat root traits and nutrient use efficiency.

根系是植物吸收养分的重要器官，在养分胁迫下根系构型能发生适应性变化以获取更多养分。已有研究表明低氮能诱导小麦根系伸长以增加其利用深层土壤中氮的能力，但低氮诱导小麦根系伸长的分子机理尚不明确。本项目拟在前期研究基础上，以主根根长对低氮响应存在显著差异的小麦近等基因系178A和178B为研究材料，从其根系表达谱中筛选对照和低氮条件下主根根尖差异表达的基因，并在拟南芥中超量表达，研究其对低氮条件下主根伸长的影响，对其所在基因通路进行分析；再从中选出作用最明显的1-2个候选基因，分别构建超表达载体和RNAi载体转化小麦，通过在小麦中超量表达和减量表达候选基因进一步研究其在低氮诱导小麦主根伸长中的作用；最后，研究候选基因所在通路上的关键基因在超表达株系和RNAi株系中的表达水平变化。通过上述研究，以期初步探明低氮诱导小麦主根伸长的分子机理，为遗传改良小麦根系性状进而提高小麦的养分利用效率提供信息。

本项目以对低氮响应存在显著差异的小麦近等基因系为材料，利用基因芯片和Realtime-PCR技术筛选出在近等基因系根尖差异表达的基因，通过转化到拟南芥和小麦中对其功能和作用机理进行了研究。结果表明，与野生型相比，超表达7号基因可以显著增加拟南芥主根长和小麦总根长、而减量表达该基因则使小麦总根长显著变短。超表达31号和59号基因可以显著增加拟南芥的总侧根长。通过对31号和59号基因拟南芥超表达系中NRT基因、生长素和乙烯等途径的基因进行检测发现，NRT1.8和NRT2家族的一些成员显著上调表达，推测31号和59号基因可能是通过NRT参与的信号途径调控了根系发育。上述研究结果增进了我们对低氮诱导小麦根系伸长分子机理的认识，并可以为遗传改良小麦根系性状和氮素利用效率提供有价值的信息。