小麦氮素依赖的类过敏性反应新基因Ndhrl1的精细定位和候选基因筛选

Development of crops with broad-spectrum and durable resistance is economically important for improving eco-adpatability and yield stability of crops in diverse eco-regions, and also for benefiting surrounding environment by reducing fungicides application. Hypersensitive reaction-like (HRL) trait shows up on the leaves of the wheat line P7001under nitrogen (N) fertilizer starvation but disppears when sufficient N is supplied, suggesting that HRL trait in P7001 is N-dosage dependent. Combining bulk segregant analysis (BSA) strategy with DNA marker and RNA-seq, we identified a N-dependent hypersensitive reaction-like gene (Ndrhrl1) and assigned it to the short arm of chromosome 2B in a population of recombinant inbred lines(F5) derived from the cross of P7001 and P216, which does not show HRL trait irrespective of N dosage. The target gene was delimited into an interval of 8.1 cM flanked by the CAPS/dCAPS markers 7hrC9 and 7hr2dc14, and co-segregated with the dCAPS marker 7hrdc2. This project aims to: fine map Ndhrl1 in heterozyotes-derived populations (F6 and F7) at target locus and predict its candidiate gene (s) ; to evaluate the effects of HRL and nitrogen levels on disease resistance of near isogenic lines (NILs) contrasting in HRL trait, to analyze the differences in tissue anatomical structure and other physicochemical parameters between the NILs, and to dissect the potential mechanisms underlying the interactions among N, HRL and disease resistance.

广谱抗性基因的挖掘和利用对提高作物的适应性、稳产性以及减少农药对环境的污染至关重要。植物类过敏性反应（HRL）通常与广谱抗病性关联。我们的研究表明，小麦品系P7001的叶片在低氮条件下表现出HRL性状且高抗白粉病，但在充足的氮素供应下该性状消失，植株对白粉病的抗性也显著降低，表明P7001携带的HRL性状是氮依赖的且与抗病性紧密关联。在低氮条件下对P7001和P216杂交衍生的329个F4和F5株系的遗传分析表明：P7001中氮依赖的HRL性状受显性单基因（Ndhrl1）控制，我们将Ndhrl1定位于2B染色体短臂。本项目拟构建F6和F7次级分离大群体并结合高密度分子标记实现Ndhrl1的精细定位；构建近等基因系并设置多梯度氮肥试验，测定相关理化指标，研究HRL-施氮量-抗病性三者的关系；整合上述研究和转录组分析，初步解析HRL性状对氮素的响应机理及其调节抗病性的关键信号路径和基因。

氮肥对作物的生长发育起着重要作用，然而氮诱导的感病性(NIS)是作物生产中的普遍现象。解析NIS的分子机制，探索不同施氮水平下维持作物抗病性的调控方法对农业生产具有重要意义。我们前期研究发现小麦品系P7001的叶片在低氮条件下表现出类过敏反应且高抗白粉病，但在高氮条件下该性状消失，对白粉病的抗性也显著降低，表明P7001携带的类过敏性状是氮依赖的且与抗病性紧密关联，我们将控制该性状的基因Ndhrl1定位于2B染色体短臂。本项目中：1）我们将Ndrhrl1精细定位于2B染色体的分子标记F4522与R0726之间47kb区域，该区间仅包含2个候选基因。2）近等基因系的显微结构观察、理化指标分析以及转录组分析表明：Ndrhrl1调控的类过敏性状与叶绿体的空泡化过程、活性氧的的爆发以及植物与病原菌的互作路径相关联。