Cassava (Manihot esculenta Crantz) is a nitrogen-efficient crop that can achieve high biomass production on poor soils. However, the mechanisms underlying the response of cassava to nitrogen-deficiency signals and the regulation of nitrogen use efficiency remain unclear. Here, we found that MeCEPD (MeGRXC1) was specifically induced by CEP6 peptides and low nitrate, and showed higher expression in leaves and stems. Overexpression of MeCEPD enhanced cassava’s tolerance to nitrate deficiency by upregulating the expression of MeNRT2.1, MeNRT2.4, and MeRBCS1A, which was manifested as increased root biomass, greater lateral root number, and darker leaf coloration. In contrast, the MeCEPD-edited lines exhibited a statistically significant reduction in root length, plant height, and biomass compared to the wild-type. Additionally, nitrate deficiency accelerated leaf senescence. Furthermore, yeast two-hybrid (Y2H) assay revealed that MeCEPD interacts with the photosynthesis-related MeRBCS1A and lateral root development-related MeLHW, which may regulate nitrogen use efficiency. Unlike its Arabidopsis thaliana homologs AtCEPD1/2 and AtCEPDL2, which interact with AtTGA1/4, MeCEPD does not interact with MeTGA1 yet still upregulates MeNRT2.1 expression. These findings contribute to our understanding of the complex regulatory mechanisms underlying cassava’s adaptation to low-nitrogen conditions and could provide new information for genetic improvement in nitrogen use efficiency in cassava.
Liu et al. (Mon,) studied this question.