Carbon-Nitrogen Interaction Modulates Plant Growth and Expression of Metabolic Genes in Rice

Carbon (C) and nitrogen (N) interact to coordinate their metabolism in achieving C:N homeostasis in all cellular organisms. Plant shoots and roots take up C and N, respectively, and the coordinated C and N assimilation is essential for normal plant growth and development. In this study, rice was used as a model system for the investigation of molecular mechanisms underlying C-N interactions and coordination in cereal species. We investigated the growth response of rice seedlings to a wide range of exogenous C:N availabilities and established balanced exogenous C:N that was optimal for rice seedling growth. To assess correlations between the modulation of plant growth and the regulation of metabolic gene expression by C:N availabilities, we examined the expression of PEPC, PK, NR, GS, and GOGAT in rice seedlings treated with four C:N availabilities: low C/low N, low C/high N, high C/low N, and high C/high N. It was found that their expression was subjected to complex regulation by C:N availabilities. Our results demonstrate that growth of shoot and root rice seedlings is regulated by C-N interaction and growth modulations are associated with changes in metabolic gene expression. Our findings suggest that rice is a useful model system for the investigation of regulation mechanisms responsible for C-N interaction and coordination in plants.