The Rice Protein Kinase PSTOL1 Confers Tolerance Of Phosphorus Deficiency

The development of phosphorus (P)-efficient rice varieties is an important measure to address the issue of diminishing and non-renewable phosphate rock reserves, the source of P fertilizer. In addition, P is often fixed in the soil as insoluble iron and aluminum complexes and therefore not easily available to plants. The major rice quantitative trait locus (QTL) for phosphorus-deficiency tolerance, Phosphorus uptake 1 (Pup1), from the rice variety Kasalath was identified more than a decade ago. Sequencing of the Pup1 locus now revealed the presence of a Kasalath-specific gene encoding a Ser/Thr protein kinase, PHOSPHORUS STARVATION TOLERANCE 1 (PSTOL1). This gene is expressed in root primordia and acts as an enhancer of root growth providing plants with an advantage in foraging the soil for P and other nutrients. Overexpression of PSTOL1 in two intolerant rice varieties, that inherently lack the gene, enhanced root growth and grain yield in P-deficient soil. Microarray analysis showed that P-starvation genes are not differentially regulated in the transgenic plants, instead, a set of genes with constitutively altered expression was identified that co-localize with known QTLs for drought tolerance and root growth. This is in agreement with a germplasm survey using Pup1-specific molecular markers that revealed high conservation of OsPSTOL1 in stress-adapted rice accessions. Importantly, Pup1 breeding lines generated through marker-assisted backcrossing showed a significant yield advantage in P-deficient soil. Introgression of this gene into local rice varieties is expected to improve rice productivity especially for poor farmers in areas with low soil P.