Abstract
Nitrate can affect many aspects of plant growth and development, such as promoting root growth and inhibiting the synthesis of secondary metabolites. However, the mechanisms underlying such effects and how plants can integrate nitrate signals and root growth needs further exploration. Here, we identified a nitrate-inducible NAC family transcription factor (TF) NAC056 which promoted both nitrate assimilation and root growth in Arabidopsis. NAC056 is a nuclear-localized transcription activator, which is predominantly expressed in the root system and hypocotyl. Using the yeast one-hybrid assay, we identified the NAC056-specific binding sequence (NAC56BM), T [T/G/A] NCTTG. We further showed that the nac056 mutant compromised root growth. NAC056 overexpression promotes LR Initiation and nitrate deficiency tolerance. Using RNA sequencing analysis and in vitro biochemical experiment, we found NAC056 regulated the expression of genes required for NO3− assimilation, directly targeting the key nitrate assimilation gene NIA1. In addition, mutation of NIA1 suppresses LR development and nitrate deficiency tolerance in the 35S::NAC056 transgenic plants. Therefore, NAC056 mediates the response of plants to environmental nitrate signals to promote root growth in Arabidopsis.
Highlights
A well-developed plant root system is critical for anchoring the plant and for absorption of nutrients and water from the soil [1]
By screening the subfamily III NAC transcription factors, we found the potential function of a new NAC family gene NAC056
NAC056 regulated the expression of genes required for NO3− assimilation, directly targeting the key nitrate assimilation gene NIA1
Summary
A well-developed plant root system is critical for anchoring the plant and for absorption of nutrients and water from the soil [1]. The RSA is the overall spatial arrangement of various parts of the root system, enabling plants to obtain sufficient resources from the soil. In Arabidopsis, LRs begin at the initials, cells that are primed in the basal meristem and activated by the initiation of xylem pole pericycle cells, and which form a single-layer lateral root primordium (LRP) through asymmetric division. These cells are produced from PR and further divide into lateral root primordia through cell separation [3,4]. Recent studies have shown that LR development in Arabidopsis is mainly regulated by auxins, and that auxin signals can regulate LRs via two regulation modules, namely IAA12–ARF5 and IAA14–ARF7/ 19 [5–7]
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