Faculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, Italy.
J Exp Bot. 2019 Feb 20;70(4):1313-1324. doi: 10.1093/jxb/ery433.
Nitrogen (N) represents one of the limiting factors for crop growth and productivity and to date has been widely supplied via external application of fertilizers. However, the use of plant growth-promoting rhizobacteria (PGPR) might represent a valuable tool to further improve plant nutrition. This study examines the influence of Azospirillum brasilense strain Cd on nitrate uptake in maize (Zea mays) plants, focusing on the high-affinity transport system (HATS). Plants were induced with nitrate (500 µM) and either inoculated or not with Azospirillum. Inoculation decreased the nitrate uptake rate in induced plants, suggesting that Azospirillum may negatively affect HATS in the short term. The expression dynamics of ZmNF-YA and ZmLBD37 suggested that Azospirillum affected the N balance in the plants, most probably by supplying them with reduced N, i.e. NH4+. This was further corroborated by measurements of total N and the expression of ammonium transporter genes. Overall, our data demonstrate that Azospirillum can counteract the plant response to nitrate induction, albeit without compromising N nutrition. This suggests that the agricultural application of microbial inoculants requires fine-tuning of external fertilizer inputs.
氮（N）是作物生长和生产力的限制因素之一，迄今为止，它主要通过外部施用肥料来提供。然而，使用植物促生根际细菌（PGPR）可能是进一步改善植物营养的有价值的工具。本研究考察了布拉氏固氮螺菌菌株 Cd 对玉米（Zea mays）植物硝酸盐吸收的影响，重点关注高亲和力转运系统（HATS）。用硝酸盐（500 µM）诱导植物，然后对其进行接种或不接种固氮菌。接种会降低诱导植物的硝酸盐吸收速率，这表明固氮菌可能在短期内对 HATS 产生负面影响。ZmNF-YA 和 ZmLBD37 的表达动态表明，固氮菌可能通过提供还原态氮（即 NH4+）来影响植物的氮平衡。这进一步得到了总氮测量和铵转运基因表达的证实。总的来说，我们的数据表明，固氮菌可以抵消植物对硝酸盐诱导的反应，尽管不会损害氮营养。这表明微生物接种剂的农业应用需要对外部肥料投入进行微调。
