Rice protein kinase OsPSTOl1 confers P. deficiency tolerance

Phosphorus (P) is an essential component of rice production systems. However, P is not easily available to plants since it may be fixed in the soil and phosphate rock, the source of P-fertilizer, is a non-renewable, limited resource. The identification of major rice quantitative trait locus (QTL) Phosphorus Uptake 1 (Pup 1) which confers tolerance to P � deficiency in rice is a significant step towards the development of P-efficient rice varieties to address such problems. However, the function of Pup 1 was not previously linked to known P-responses and the tolerance mechanism remains unclear. Sequencing of the tolerant donor parent Kasalath Pup 1 Ilocos revealed candidate genes, which are not obviously related to P-deficiency tolerance. Interestingly, a Kasalath-specific insertion-deletion (approximately 90 kbp) region contains the PHOSPHORUS STARVATION TOLERANCE 1 (OsPSTOL 1) gene which is absent in intolerant varieties. Over expression of the OsPSOTOL 1 gene in varieties that lack the gene (i.e., IR64 and Nipponbare) revealed that high level of transgene expression confers tolerance to P deficiency as demonstrated by higher grain weight. Additionally, IR64 transgenic plants showed higher root biomass and total P content. The transgenic plants, as well as IR64- and IR74-Pup 1 near isogenic lines (NILs) exhibited constitutive early vigorous root growth in low and high P culture solution suggesting that OsPSTOL 1/Pup 1 is involved in early root development. In agreement with this, OsPSTOL 1 promoter-GUS transgenic plants showed GUS staining in parenchymatic cells and crown root primodia in the coleoptilar node where the crown roots emerge. Furthermore, microarray analysis using the roots of the over expression plants suggests that genes involved in root development and stress response are downstream of OsPSTOL 1. The authors conclude that OsPSTOL 1 is the major genetic determinant in the Pup 1 locus and confers tolerance by enhancing root growth providing plants with an advantage in the access to P and other soil nutrients.