Early molecular events associated with nitrogen deficiency in rice seedling roots

Nitrogen (N) deficiency is one of the most common problems in rice. The symptoms of N deficiency are well documented, but the underlying molecular mechanisms are largely unknown in rice. Here, we studied the early molecular events associated with N starvation (-N, 1 h), focusing on amino acid analysis and identification of -N-regulated genes in rice roots. Interestingly, levels of glutamine rapidly decreased within 15 min of -N treatment, indicating that part of the N-deficient signals could be mediated by glutamine. Transcriptome analysis revealed that genes involved in metabolism, plant hormone signal transduction (e.g. abscisic acid, auxin, and jasmonate), transporter activity, and oxidative stress responses were rapidly regulated by -N. Some of the -N-regulated genes encode transcription factors, protein kinases and protein phosphatases, which may be involved in the regulation of early -N responses in rice roots. Previously, we used similar approaches to identify glutamine-, glutamate-, and ammonium nitrate-responsive genes. Comparisons of the genes induced by different forms of N with the -N-regulated genes identified here have provided a catalog of potential N regulatory genes for further dissection of the N signaling pathwys in rice.