Transcriptome profiling characterizes phosphate deficiency effects on carbohydrate metabolism in rice leaves

Phosphorus (P) is a structural component of nucleic acids and phospholipids and plays important roles in plant growth and development. P accumulation was significantly reduced (about 35%) in rice leaves from plants grown under low (32 μM) P compared to 320 μM P grown plants. Genome response to low P was examined using the rice 60K oligonucleotide DNA microarrays. At the threshold significance of |log₂| fold>2.0, 21,033 genes (about 33.7% of all genes on the microarray) were affected by P deficiency. Among all genes on the microarray, 4271 genes were sorted into 51 metabolic pathways. Low P affected 1494 (35.0%) genes and the largest category of genes was related to sucrose degradation to ethanol and lactate pathway. To survey the role of P in rice, 25 pathways were selected based on number of affected genes. Among these pathways, cytosolic glycolysis contained the least number of upregulated but most down-regulated genes. Low P decreased glucose, pyruvate and chlorophyll, and genes related to carbon metabolism and chlorophyllide a biosynthesis. However, sucrose and starch levels increased. These results indicate that P nutrition affects diverse metabolic pathways mostly related to glucose, pyruvate, sucrose, starch, and chlorophyll a.