To maximize the yield of maize crop in the field, large quantities of nitrogenous fertilizers are added to the soil during cultivation. Approximately 70% of the kernel weight in maize is composed of starch, which is the main source of energy in the human and animal diet. Maize ( Zea mays) is one of the most important crops in the world. Our results provide novel insights into the role of chromatin remodeling proteins in the regulation of nitrate-responsive gene expression in plants. However, in the presence of nitrate, the binding affinity of ZmCHB101 for NREs decreased dramatically, leading to reduced nucleosome density at NREs and consequently increased ZmNLP3.1 binding. The ZmCHB101 protein bound to NREs and was involved in the maintenance of nucleosome occupancies at these sites, which may impact the binding of ZmNLP3.1 to NREs in the absence of nitrate. Intriguingly, well-positioned nucleosomes were detected at NREs in the ZmNRT2.1 and ZmNRT2.2 gene promoters, and nucleosome densities were lower in ZmCHB101-RNAi lines than in wild-type plants, both in the absence and presence of nitrate. The NIN-like protein (NLP) of maize, ZmNLP3.1, recognized the consensus nitrate-responsive cis-elements (NREs) in the promoter regions of ZmNRT2.1 and ZmNRT2.2, and activated the transcription of these genes in response to nitrate. An RNA sequencing analysis revealed that ZmCHB101 regulates the expression of genes involved in nitrate transport, including ZmNRT2.1 and ZmNRT2.2. ZmCHB101-RNAi lines showed accelerated root growth and increased biomass under low nitrate conditions. Here, we demonstrate that ZmCHB101 plays a pivotal regulatory role in nitrate-responsive gene expression. RNA-interference transgenic plants ( ZmCHB101-RNAi) display abaxially curling leaves and impaired tassel and cob development.
ZmCHB101 is the core subunit of the SWI/SNF-type ATP-dependent chromatin remodeling complex in maize.
However, the specific transcriptional machineries involved in this process and the detailed transcriptional regulatory mechanism of the core HATS remain poorly understood. Rapid transcriptional activation of genes encoding the high-affinity nitrate transport system (HATS) is an important strategy that plants use to cope with nitrogen deficiency. Nitrate is the main source of nitrogen for plants and an essential component of fertilizers.
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