Transcriptomic analysis indicates putative metabolic changes caused by manipulation of phosphorus availability in rice leaves

Plants have developed several strategies for coping with phosphorus (P) deficiency. However, the details of the regulation of gene expression of adaptations to low P are still unclear. Using a cDNA microarray, transcriptomic analyses were carried out of the rice genes regulated by P deficiency and P re-supply to P-deficient plants. The OsPI1 gene, which was isolated as the most significant up-regulated gene under -P conditions, was also the most significant down-regulated gene following P re-supply. Many starch metabolism-related genes, as well as several genes for P(i)-liberating enzymes, were up-regulated by -P treatment, suggesting a homeostatic contribution to the P(i) concentration in leaf tissues. mRNAs for glucanases were also induced by P re-supply: these are suspected to play a role in loosening the cell wall compounds. Most of the genes up-regulated by -P treatment were down-regulated by P re-supply, suggesting that their responses were specific to -P conditions. Conversely, the number of genes up-regulated by P re-supply was also larger following P re-supply than in the -P condition. It is proposed that the genes up-regulated by P re-supply play an important role in P acquisition by P-deficient plants.