Oszvald Maria, Hassall Kirsty L, Hughes David, Torres-Ballesteros Adriana, Clark Ian, Riche Andrew B, Heuer Sigrid
Plant Science Department, Rothamsted Research, Harpenden, United Kingdom.
Computational and Analytical Sciences, Rothamsted Research, Harpenden, United Kingdom.
Front Plant Sci. 2022 May 4;13:816475. doi: 10.3389/fpls.2022.816475. eCollection 2022.
Crops assimilate nitrogen (N) as ammonium via the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway which is of central importance for N uptake and potentially represents a bottle neck for N fertiliser-use efficiency. The aim of this study was to assess whether genetic diversity for N-assimilation capacity exists in wheat and could be exploited for breeding. Wheat plants rapidly, within 6 h, responded to N application with an increase in GS activity. This was not accompanied by an increase in GS gene transcript abundance and a comparison of GS1 and GS2 protein models revealed a high degree of sequence conservation. N responsiveness amongst ten wheat varieties was assessed by measuring GS enzyme activity, leaf tissue ammonium, and by a leaf-disc assay as a proxy for apoplastic ammonia. Based on these data, a high-GS group showing an overall positive response to N could be distinguished from an inefficient, low-GS group. Subsequent gas emission measurements confirmed plant ammonia emission in response to N application and also revealed emission of NO when N was provided as nitrate, which is in agreement with our current understanding that NO is a by-product of nitrate reduction. Taken together, the data suggest that there is scope for improving N assimilation capacity in wheat and that further investigations into the regulation and role of GS-GOGAT in NH emission is justified. Likewise, emission of the climate gas NO needs to be reduced, and future research should focus on assessing the nitrate reductase pathway in wheat and explore fertiliser management options.
作物通过谷氨酰胺合成酶/谷氨酸合酶（GS/GOGAT）途径将氮（N）同化为铵，该途径对于氮的吸收至关重要，并且可能是氮肥利用效率的一个瓶颈。本研究的目的是评估小麦中是否存在氮同化能力的遗传多样性，以及这种多样性是否可用于育种。小麦植株在施氮后6小时内迅速做出反应，GS活性增加。但这并未伴随着GS基因转录丰度的增加，对GS1和GS2蛋白质模型的比较显示出高度的序列保守性。通过测量GS酶活性、叶片组织铵含量以及采用叶盘试验作为质外体氨的替代指标，评估了十个小麦品种对氮的响应能力。基于这些数据，可以区分出对氮总体呈阳性反应的高GS组和低效的低GS组。随后的气体排放测量证实了施氮后植物的氨排放，并且还发现当以硝酸盐形式提供氮时会有一氧化氮排放，这与我们目前认为一氧化氮是硝酸盐还原副产物的理解一致。综合来看，数据表明提高小麦氮同化能力具有潜力，并且对GS-GOGAT在氨排放中的调节和作用进行进一步研究是合理的。同样，需要减少气候气体一氧化氮的排放，未来的研究应侧重于评估小麦中的硝酸还原酶途径并探索肥料管理方案。
