花生荚果氮素吸收利用特征及分子机理研究

Peanut (Arachishypogaea L.) is an important oil crops and economic crops in the world. Although the use of nitrogen fertilizer was increasing rapidly recently, the yield of peanut was not significantly increased. The low utilization ratio of nitrogen fertilizer has become a prominent problem in peanut nutrition management. Unlike most other crops, the nitrogen in the soil can be absorbed by the geocarpic pods in peanut. However, the molecular mechanism of the nitrogen absorption in pods is poorly understood. To distinguish the nitrogen absorption between roots and pods, we previous designed an equipment to separate the soil environment of roots and pods. On the basis of this equipment, following studies will be performed in the present study: (1)Analysis the dynamic changing of nitrogen absorption in pods and roots during the pod development. (2)Study the effect of nitrogen fertilizer on pod development, nitrogen absorption and protein accumulation by application of nitrogen in different stages. (3)Elucidation the changes of the peanut transcriptome under different nitrogen stress treatment using high-throughput sequencing technology, and identification the differential expressed genes related with nitrogen absorption. (4)According to the results of gene expression profiles, identification the key genes related with nitrogen absorption, and study its’ role in regulation of yield and quality of peanut pods. The results of this study will provide a deeper insight into the molecular mechanism of nitrogen absorption of peanut pods, and provide theoretical basis and technical support for improving the utilization efficiency of nitrogen fertilizer in peanut.

花生是重要油料和经济作物，氮肥用量高速增长与产量增加缓慢和氮肥利用率低的矛盾是花生营养管理的突出问题。与其他作物不同，花生地上开花地下结果，荚果可以从土壤中吸收营养元素。本项目拟以花生荚果为研究对象，采用根区和结荚区分离方法，通过结荚区施肥，重点研究：（1）荚果发育过程中氮素吸收关键时期、吸收量与分配比例；（2）在荚果不同发育阶段结荚区施氮对荚果发育、氮素吸收、蛋白质合成与氮肥利用的调控效应；（3）利用高通量测序技术，比较优化供氮和氮胁迫下，不同发育阶段荚果基因表达谱的差异，阐明荚果中与氮吸收相关基因的表达及调控信息；（4）根据基因表达谱的分析结果，研究不同发育阶段荚果氮素吸收关键基因、氮代谢关键酶活性与其基因的表达变化规律，及对花生产量和蛋白质含量的影响。预期研究结果将阐明花生荚果氮素吸收特性及分子机理，丰富植物养分吸收理论，为创新提高花生产量和氮肥利用率的精准施肥方案提供理论依据。

花生是一种地下结果作物，不仅可以通过根系吸收营养，而且可通过荚果吸收营养。本研究通过分离花生根区和结荚区，在结荚区设置不同施氮量，研究了花生荚果氮素吸收的特征及分子机制。15N同位素示踪表明，荚果氮吸收量随结荚区施氮量增加而增加，约占植株总氮量的10%左右，其中约80%保留在果壳和籽仁中，根区氮肥不足时，荚果吸收氮素更多的转移到营养器官。对不同发育阶段的花生幼果进行RNA-Seq分析，结荚区施氮促使激素信号途径和氮代谢途径出现富集，显著上调了氮素吸收同化、赤霉素和油菜素内酯生物合成途径的相关基因。结荚区施氮显著增加了花生产量，施纯氮60 kg•hm-2增产幅度最大，对大粒型花生的增产效果优于小粒型花生，氮素增幅也大于小粒型花生，尤其是促进了荚果发育后期的氮素积累。结荚区施氮显著上调了荚果氮代谢相关基因（NR、NIR、ABC、NRTS2、GS、NADH-GOGAT）的相对表达量，大粒型和小粒型花生分别在荚果发育30 d和20 d相对表达量最大，大粒型花生相关基因表达量一直大于小粒型花生，荚果发育20 d基因相对表达量随施氮量增加而增加，至30 d时60 kg•hm-2处理最高，品种间变化规律基本一致。荚果NR、GS和GOGAT等氮代谢关键酶活性对结荚区施氮的响应规律与基因表达量相吻合。相关分析表明，以上氮代谢相关酶活性和基因相对表达量在荚果不同发育时期与产量和氮素积累量显著正相关。综合分析花生产量、氮素积累量、氮肥利用率和品质，在大粒型花生果针入土10~20 d，小粒型花生果针入土1~10 d结荚区施氮，是协调提高花生产量和氮肥利用率的最佳施肥方案，最佳施氮量为60 kg•hm-2。研究结果阐明了花生荚果氮素吸收特性及机理，并提出了合理施肥方案，为花生高产及氮肥高效利用奠定了理论基础。