The Overexpression of NUC Promotes Development and Increases Resistance to Nitrogen Deficiency in Arabidopsis thaliana

NUTCRACKER (NUC) is a transcription factor expressed in multiple tissues, but little is known about its physiological roles. In this study, we explored the physiological function of NUC with the Arabidopsis knockout, rescue, and overexpression lines. We found that NUC overexpression promoted development at the germination, seedling, and juvenile stages. NUC overexpression increased resistance to nitrogen (N) deficiency stress by increasing the chlorophyll content, suppressing anthocyanin accumulation, and increasing the biomass under N deficiency. In contrast, the absence of NUC did not affect such characteristics. N deficiency significantly increased the expression of NUC in leaves but did not affect the expression of NUC in roots. The overexpression of NUC promoted primary root length under both normal and N deficiency conditions. Furthermore, we found that the N-responsive and lateral-root-related genes TGA1 and NRT2.4 had NUC-binding sites in their promoter regions and that their expression was upregulated by NUC under N deficiency. The overexpression of the NUC increased the number and length of the lateral roots under N deficiency through inducible promotion. Multiple lines of investigation suggest that the regulatory function of the NUC could be bypassed through its redundant MAGPIE (MGP) when the NUC is absent. Our findings provide novel insight into NUC's functions and will assist efforts to improve plants' development and resistance to nutrient stresses.