后期供氮优化面筋蛋白及亚基组成提高小麦籽粒加工品质的机理

The concentration and composition of gluten proteins play crucial roles in determining wheat grain processing quality. Late nitrogen (N) fertilization is an effective practice to improve processing quality of wheat grains. Our previous studies indicated that late N fertilization improved baking quality of wheat flour, which mainly resulted from the effect of N splitting. Nitrogen splitting changed N partitioning in wheat grain, which was decisive for baking quality. However, the mechanism behind late N fertilization on N partitioning in wheat gluten proteins was unclear and needed to be further studied. Moreover, we also found that there might be a critical growth stage for late N application. The effect of late N fertilization on baking quality of wheat grain might not be achieved if the late N was applied before or after this certain stage. Based on our previous results and inference, the present study will be focused on exploring the key period for late N application in quality wheat production and the mechanism of late N fertilization on gluten proteins synthesis. The study will be conducted using pot experiments. The first pot experiment consists of treatments with late N fertilizer application at different growth stages (booting, heading and anthesis) of winter wheat. The techniques including sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), farinograph analysis and baking test et al. will be used to investigate the patterns and mechanism of different N application timing on baking quality of wheat grain. Based on results from the first pot experiment, the second pot experiment will be conducted consists of treatment with late N application at the critical (optimal) and non-critical stages for quality wheat production. In the second pot experiment, the late N fertilizer will be labeled with 15N. The changes of N and sulfur concentration and amino acids composition during wheat growth and the distribution of late N in amino acids composition and different storage protein fractions in grain will be determined using instruments such as stable isotope ratio mass spectrometry, gas chromatography-mass spectrometer (GC-MS) aiming to explain the mechanism of late N application at critical growth stage on processing quality of wheat flour through the changes in N partitioning among different protein fractions, which will make contributions to the theories and practices on quality wheat production.

面筋蛋白含量与组成对小麦籽粒加工品质至关重要，后期施氮是改善小麦籽粒加工品质的重要途径。本项目组前期研究表明：后期施氮提高小麦籽粒烘焙品质的关键在于改变了氮素在不同面筋蛋白组分及其亚基间的分配，然而其作用机理尚未明确，亟待深入研究；此外，还发现存在小麦后期施氮的关键期，早于或晚于该时期施氮对其烘焙品质的改善效果不显著。基于此，本项目拟通过盆栽试验，首先设置不同追氮时期，采用聚丙烯酰胺凝胶电泳、粉质仪及烘焙测试等分析手段，明确不同追氮时期对小麦籽粒蛋白质组成及其加工品质的影响规律；进而优化氮素调控期，利用同位素标定后期施氮，采用同位素质谱仪、气相色谱-质谱仪等分析手段，研究强筋小麦不同生育期氮、硫分配，氨基酸组成以及后期追肥中氮素在不同器官中累积、转移及籽粒不同蛋白质组分中分配过程，揭示关键期追氮通过改变氮素在不同蛋白质组分中分配提高其加工品质的机理，为优质小麦生产提供理论依据和技术支撑。

面筋蛋白含量与组成对小麦籽粒加工品质至关重要，后期施氮是改善小麦籽粒加工品质的重要途径。本项目组前期研究表明：后期施氮提高小麦籽粒烘焙品质的关键在于改变了氮素在不同面筋蛋白组分及其亚基间的分配，然而其作用机理尚未明确，亟待深入研究；此外，还发现存在小麦后期施氮的关键期，早于或晚于该时期施氮对其烘焙品质的改善效果不显著。基于此，本项目拟通过大数据分析、大田试验和盆栽试验相结合，首先通过文献调研调查中国小麦品质质量状况和变异情况，揭示品质相关参数之间的相关性。通过meta分析探究后期施氮对优质冬小麦生产中品质调控的效果及影响因素，明确调控小麦籽粒加工品质的关键追氮期及其关键影响因素。通过大田试验和盆栽试验，设置不同追氮时期，明确不同追氮时期对小麦籽粒蛋白质组成及其加工品质的影响规律；进而优化氮素调控期，分析强筋小麦不同生育期氮、硫分配，氨基酸组成以及后期追肥中氮素在不同器官中累积、转移及籽粒不同蛋白质组分中分配过程，揭示了孕穗期作为后期施氮关键期通过改变氮素在不同蛋白质组分中的分配，协调碳水化合物和蛋白质合成与累积，实现小麦产量与品质协同提高的机理，为优质小麦生产提供理论依据和技术支撑。