Zanin Laura, Tomasi Nicola, Zamboni Anita, Varanini Zeno, Pinton Roberto
Department of Agricultural and Environmental Sciences, University of Udine Udine, Italy.
Department of Biotechnology, University of Verona Verona, Italy.
Front Plant Sci. 2015 Nov 19;6:1007. doi: 10.3389/fpls.2015.01007. eCollection 2015.
Despite the widespread use of urease inhibitors in agriculture, little information is available on their effect on nitrogen (N) uptake and assimilation. Aim of this work was to study, at physiological and transcriptional level, the effects of N-(n-butyl) thiophosphoric triamide (NBPT) on urea nutrition in hydroponically grown maize plants. Presence of NBPT in the nutrient solution limited the capacity of plants to utilize urea as a N-source; this was shown by a decrease in urea uptake rate and (15)N accumulation. Noteworthy, these negative effects were evident only when plants were fed with urea, as NBPT did not alter (15)N accumulation in nitrate-fed plants. NBPT also impaired the growth of Arabidopsis plants when urea was used as N-source, while having no effect on plants grown with nitrate or ammonium. This response was related, at least in part, to a direct effect of NBPT on the high affinity urea transport system. Impact of NBPT on urea uptake was further evaluated using lines of Arabidopsis overexpressing ZmDUR3 and dur3-knockout; results suggest that not only transport but also urea assimilation could be compromised by the inhibitor. This hypothesis was reinforced by an over-accumulation of urea and a decrease in ammonium concentration in NBPT-treated plants. Furthermore, transcriptional analyses showed that in maize roots NBPT treatment severely impaired the expression of genes involved in the cytosolic pathway of ureic-N assimilation and ammonium transport. NBPT also limited the expression of a gene coding for a transcription factor highly induced by urea and possibly playing a crucial role in the regulation of its acquisition. This work provides evidence that NBPT can heavily interfere with urea nutrition in maize plants, limiting influx as well as the following assimilation pathway.
尽管脲酶抑制剂在农业中广泛使用，但关于它们对氮（N）吸收和同化作用的信息却很少。这项工作的目的是在生理和转录水平上研究N-（正丁基）硫代磷酸三酰胺（NBPT）对水培玉米植株尿素营养的影响。营养液中NBPT的存在限制了植株将尿素作为氮源利用的能力；这表现为尿素吸收速率和（15）N积累量的降低。值得注意的是，这些负面影响仅在植株以尿素为养分时才明显，因为NBPT不会改变以硝酸盐为养分的植株中的（15）N积累。当以尿素作为氮源时，NBPT也会损害拟南芥植株的生长，而对以硝酸盐或铵盐生长的植株没有影响。这种反应至少部分与NBPT对高亲和力尿素转运系统的直接作用有关。使用过表达ZmDUR3的拟南芥株系和dur3基因敲除株系进一步评估了NBPT对尿素吸收的影响；结果表明，该抑制剂不仅会影响转运，还可能损害尿素同化。NBPT处理的植株中尿素的过度积累和铵浓度的降低进一步支持了这一假设。此外，转录分析表明，在玉米根中，NBPT处理严重损害了参与尿素氮同化的胞质途径和铵转运相关基因的表达。NBPT还限制了一个编码转录因子的基因的表达，该转录因子受尿素高度诱导，可能在尿素获取的调控中起关键作用。这项工作提供了证据，证明NBPT会严重干扰玉米植株的尿素营养，限制其流入以及后续的同化途径。
