The nitrate-inducible NAC transcription factor NAC056 controls nitrate assimilation and promotes lateral root growth in Arabidopsis thaliana.

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. Author summary: Nitrogen is not only a major nutrient element in plants, but also an important signal molecule for plant growth and metabolism. However, the underlying molecular mechanism of nitrate signal transduction, leading to root development response, is still unclear. In this study, by screening the subfamily III NAC transcription factors, we found the potential function of a new NAC family gene NAC056. The nac056 mutant compromised root growth. NAC056 overexpression promoted lateral root initiation and tolerance of nitrate deficiency. NAC056 regulated the expression of genes required for NO3− assimilation, directly targeting the key nitrate assimilation gene NIA1. In a high-nitrate environment, relatively high levels of NAC056 expression promoted nitrate assimilation, further enhancing root growth. These findings reveal an important role for the nitrate-inducible NAC056 gene in promoting nitrate assimilation and root growth in Arabidopsis. [ABSTRACT FROM AUTHOR]