Graduate School of Agricultural Science, Tohoku University, Sendai, Japan.
Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Physiol Plant. 2021 Apr;171(4):802-808. doi: 10.1111/ppl.13303. Epub 2020 Dec 14.
Urea is the most used nitrogenous fertilizer worldwide and an important nitrogen-containing plant metabolite. Despite its major use as fertilizer, its direct uptake is limited due to the ubiquitous presence of bacterial urease, which leads to the formation of ammonium. In this review, we will focus mainly on the more recent research about the high-affinity urea transporter function in nitrogen-deficient conditions. The effective use of nitrogenous compounds is essential for plants to be able to deal with nitrogen-deficient conditions. Leaf senescence, either induced by development and/or by nitrogen deficiency, plays an important role in the efficient use of already assimilated nitrogen. Proteinaceous nitrogen is set free through catabolic reactions: the released amino acids from protein catabilization are in turn catabolized leading to an accumulation of ammonium and urea. The concentration and conversion to transportable forms of nitrogen, e.g. amino acids like glutamine and asparagine, are coordinated around the vascular tissue. Urea itself can be translocated directly over the phloem by a mechanism that involves DUR3, or it is converted by urease to ammonium and assimilated again into amino acids. The details of the high-affinity transporter function in this physiological context and the implications for crop yield are explained.
尿素是全球使用最广泛的氮肥，也是一种重要的含氮植物代谢物。尽管它主要用作肥料，但由于普遍存在的细菌脲酶，其直接吸收受到限制，因为脲酶会导致铵的形成。在这篇综述中，我们将主要关注在氮缺乏条件下高亲和力尿素转运蛋白功能的最新研究。有效的氮化合物利用对植物在氮缺乏条件下的生存至关重要。叶片衰老，无论是由发育和/或氮缺乏引起的，在有效利用已同化的氮方面起着重要作用。通过分解代谢反应释放出蛋白质氮：从蛋白质分解中释放的氨基酸被进一步分解，导致铵和尿素的积累。氮的浓度和转化为可运输的形式，如谷氨酸和天冬酰胺等氨基酸，在维管束组织周围协调。尿素本身可以通过涉及 DUR3 的机制直接在韧皮部中转运，或者被脲酶转化为铵并再次被同化到氨基酸中。解释了这种生理背景下高亲和力转运蛋白功能的细节及其对作物产量的影响。
