水稻OsAMT1;1过表达提升氮肥减施情境下的氮素利用效率

水稻铵转运蛋白AMT1;1是根系获取土壤氮素(铵态氮)的重要组分,同时参与氮素向地上部的转运。针对稻田施氮过量导致的环境风险和氮素利用效率趋缓的现状,亟需探究既能减少氮肥投入又能维持现有生产水平的调控策略。本研究利用OsAMT1;1过表达水稻材料,设置氮缺乏(LN, 不施氮)、减氮投入(MN, 200 kg hm_^-2)和过量施氮(HN, 350 kg hm_^-2)三个处理水平的田间试验,用以评估OsAMT1;1过表达株系在关键生育期的氮素生产特性。结果表明：在LN条件下,OsAMT1;1过表达相比野生型能够明显改善植株和剑叶氮素营养状态,有利于植株生物量的积累和产量形成。在MN条件下,促进植株在齐穗期至完熟期的生长速率和生物量积累；灌浆期,过表达单株和剑叶含氮量相比野生型分别增加22.95%和29.53%,光合效率(Pn)和气孔导度(g_s)分别增加40.71%和19.39%,千粒重和产量平均增加10.26%和27.36%,氮肥吸收效率(RE_N)和氮素干物质生产效率(NUEb)显著提升,对氮素生理效率(PE_N)和氮肥农学效率(AE_N)有促进作用但并不显著。在HN条件下,该基因过表达在灌浆期的植株含氮量较野生型平均高出22.64%,提升了RE_N,灌浆阶段植株生物量的增加和Pn趋于饱和,PE_N和AE_N均显著降低。可见,与过量施氮(当前施氮习惯)相比,OsAMT1;1过表达在减少氮投入时更有利于协同植株高氮的内部环境实现相当的产量水平,提高水稻氮素利用效率。

OsAMT1;1 Overexpression Improves Nitrogen Use Efficiency Under Reduced Nitrogen Input in Rice

Rice ammonium transporter AMT1;1 is not only an important component of soil NH4⁺-N acquisition by roots, but also involved in N transportation to shoot. In view of the current situation of environmental risks and slowing N use efficiency caused by excessive N fertilizer input in paddy soil. It is necessary to search for the regulation strategies that can reduce N fertilizer input and maintain the current production level. In this study, a field experiment was conducted with OsAMT1;1 overexpression genetic lines by three N treatments including N deficient (LN, no N application), moderate or reduced N input (MN, 200 kg hm^-2) and N fertilizer overuse (HN, 350 kg hm^-2). It was used to evaluate the N production characteristics in the later growth period. The results showed that, under the LN condition, OsAMT1;1 overexpression significantly improved plant and flag leaf nitrogen status, as well as enhanced the biomass accumulation and yield formation compared with wild-type(WT). Under the condition of reduced nitrogen input (MN), the biomass of WT and overexpression lines increased from the heading stage to the full maturity stage compared with the LN during the full maturity. At the grain filling stage, the N content of per plant and flag leaf of overexpression lines increased by 22.95% and 29.53% respectively, and the photosynthetic efficiency(Pn) and stomatal conductance(gs) increased by 40.71% and 19.39% respectively compared with the WT. This treatment enhanced the 1000-grain weight and yield by 10.26% and 27.36% respectively compared with the WT. The recovery N use efficiency (REN) and N use efficiency for biomass production(NUEb) were significantly improved, the physiological N use efficiency (PEN) and agronomic N use efficiency (AEN) were boosted, but not significant compared with the WT. In addition, under the condition of N fertilizer overuse (HN, 350 kg hm^-2), the OsAMT1;1 overexpressing enhanced N content by 22.64% compared with the WT. This treatment could also improve the recovery N use efficiency (REN), but the plant biomass and photosynthetic efficiency tended to be saturated at the grain filling stage, the physiological N use efficiency (PEN) and agronomic N use efficiency (AEN) decreased significantly. Compared with N fertilizer overuse (current N input habits), OsAMT1;1 overexpression lines were more favorable to collaborate the high N internal environment of the plant to achieve higher yield and to improve the N use efficiency of rice in the moderate or reduced N input.