Identification of temporally and spatially phosphate-starvation responsive genes in Glycine max

Low phosphorus (P) availability is a major constraint to the production of soybean (Glycine max (L.) Merr.), an important leguminous crop in the world. To gain a better insight into the molecular mechanisms by which soybean adapts to low P availability, a P-efficient soybean genotype, BX10, was used to identify phosphate-starvation responsive genes from four cDNA libraries constructed by suppression subtractive hybridization. The results showed that 215 represented genes selected were differentially expressed in the roots and shoots of soybean subjected to either short-term (0.5–12 h) or long-term (3–12 days) Pi starvation (0.2 μM Pi). The selected genes were categorized into five groups representing Metabolism, Genetic Information Processing, Interaction with the Environment, Development, and Unknown Function. Comparison of the relative proportion of genes belonging to different categories in the four libraries indicated distinct spatial and temporal expression patterns of the genes. Transcripts of many genes were induced by short-term Pi starvation in roots, but not in shoots. Furthermore, the largest group of genes from the root long-term library was under the Genetic Information Processing category, whereas the largest group from shoot long-term library was involved in Metabolism, indicating that shoots and roots of soybeans respond differently to long-term Pi starvation. Differential expression of twelve genes belonging to different libraries was further confirmed by quantitative real-time PCR analysis. Our study has demonstrated that various genes are spatially and temporally integrated in soybean plant in response to Pi starvation.