Function analysis of nitrogen-responsive transcription factor ZmNLP5 affecting root growth in maize

Abstract

<p indent=0mm>Improving nitrogen (N) use efficiency of crops is crucial for minimizing N loss and reducing environmental pollution, which is a requirement for the sustainable agriculture. Our previous study found that the transcription factor ZmNLP5 directly regulated the expression of <italic>ZmNIR1</italic>.<italic>1</italic> and promoted nitrogen uptake and assimilation in maize, however, its underlying regulation mechanism is unclear. Here, we performed further phenotype analysis of <italic>zmnlp5 </italic>and wild type (W22) plants in hydroponic culture on sufficient nitrogen (SN) solution and deficient nitrogen (DN) solution. Compared with WT plants, the root length of <italic>zmnlp5</italic> mutant plants was significantly decreased under DN condition. Compared with upper and middle regions of roots, ZmNLP5 was predominantly expressed in root tip regions. Then, we examined the relationship between root length and nitrite content in root tips under a series of nitrite concentrations. The results showed that there was no significant differences in root length between WT and <italic>zmnlp5</italic> until the nitrite concentration reached <sc>2 mmol L^–1</sc> and higher; however, when the concentration of nitrite was higher than <sc>2 mmol L^–1,</sc> the root length of <italic>zmnlp5</italic> was significantly shorter than WT, and the accumulation of nitrite in the root tips of <italic>zmnlp5</italic> was significantly higher than WT. Interestingly, <italic>zmnlp5 </italic>plants also accumulated significantly more nitrite in the root tips than WT under DN condition. The study showed that the transcription factor ZmNLP5 played an important role in the root growth of maize in response to deficient nitrogen condition, and provided the candidate genes for breeding of maize nitrogen use efficiency in the future.