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ZmNRT1.1B (ZmNPF6.6) determines nitrogen use efficiency via regulation of nitrate transport and assimilation in maize

ABSTRACT: Nitrate (NO3-) is crucial for optimal plant growth and development and often limits crop productivity at the low availability. In comparison with model plant Arabidopsis, the molecular mechanisms underlying NO3- acquisition and utilization remain largely unclear in maize. In particular, only a few genes have been exploited to improve nitrogen use efficiency (NUE). Here, we demonstrated that NO3--inducible ZmNRT1.1B (ZmNPF6.6) positively regulated NO3--dependent growth and NUE in maize. We showed that the tandem duplicated proteoform ZmNRT1.1C is irrelevant to maize seedling growth under nitrate supply, however, loss-of-function of ZmNRT1.1B significantly weakened plant growth under adequate NO3- supply in both hydroponic and field conditions. 15N-labeled NO3- absorption assay indicated that ZmNRT1.1B mediated high-affinity NO3--transport and root-to-shoot NO3- translocation. Furthermore, upon NO3- supply, ZmNRT1.1B promotes cytoplasmic-to-nuclear shuttling of ZmNLP3.1 (ZmNLP8), which co-regulates the expression of genes involved in NO3- response, cytokinin biosynthesis and carbon metabolism. Remarkably, overexpression of ZmNRT1.1B in modern maize hybrids improved grain yield under nitrogen (N) limiting fields. Taken together, our study revealed a crucial role of ZmNRT1.1B in high-affinity NO3- transport and signaling and offers valuable genetic resource for breeding nitrogen use efficient high-yield cultivars.

ORGANISM(S): Zea mays

PROVIDER: GSE227472 | GEO | 2023/04/25

REPOSITORIES: GEO

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Project description:Arable soils are extremely heterogeneous in spatial nutrient distribution. It is well documented that lateral roots (LRs) proliferate in nitrate-rich patch. Yet less information is available as to which genes are involved in this process, in particular in cereals. To understand the molecular mechanism for local nitrate induced LR growth in maize (Zea mays L.), we analyzed the gene expression profiling in maize root in early response (1 hour) to local nitrate stimulation by using Maize Oligonucleotide Array (http://www.maizearray.org) and a split-root system. Selected differentially expressed genes were further confirmed by semi-quantitative RT-PCR. The results showed that reception and/or transduction of local NO3- signal involve some important protein kinases and protein phosphatases (histidine kinases, serine/threonine kinases, protein phosphatase 2A etc.) and transcription factors (F-box, Zinc finger, Myb and bZIP transcription factors and response regulator). Increasing expression of genes encoding auxin response factor 7b, ethylene receptor, and cytokinin oxidase suggests strong interaction among hormonal pathways and local NO3- signaling pathways. Genes involving NO3- uptake and assimilation (NRT2.1, NR, etc.), sugar transport (a sugar transporter) and utilization (a sucrose synthase) were enhanced in the N-fed root. Furthermore, local NO3- induces rapid expression of genes related to cell division and expansion such as alpha-expansin, celluose synthase, kinesin, plasma membrane and tonoplast aquaporins. Based on the differentially expressed genes, a putative model which combines both the 'NO3- signal' and 'metabolic sink' theories is proposed to explain the molecular mechanism controlling local nitrate induced LR elongation in maize. plants were pre-cultured in solution containing 0.5 mmol L-1 NO3- for 6 days and then transferred to N-free solution to grow for another 2 days. Then these plants were transferred to a two-compartment split-root system with only half root supplied with 1.0 mmol L-1 NO3-. Supply of Ca2+ in the N-free half was compensated by adding 1.0 mmol L-1 CaCl2. One hour after the local nitrate treatment, root segments (15cm from root tip to lateral root elongation zone) were sampled for RNA extraction. Two biological replicates were performed for each treatment.

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ZmNRT1.1B (ZmNPF6.6) determines nitrogen use efficiency via regulation of nitrate transport and assimilation in maize

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