LAUSR

Recent progress has shown that the preferential distribution of mineral nutrients is mediated by node-based transporters in gramineous plants, but it is poorly understood for the mechanisms of preferential distribution in dicots. Here, we report a distinct mechanism for the preferential distribution of phosphorus (P) through detailed functional analysis of AtSPDT/AtSULTR3;4 (SULTR-like P Distribution Transporter) in Arabidopsis. AtSPDT is a homolog of rice OsSPDT and localized to the plasma membrane. It also showed proton-dependent transport activity for P. AtSPDT was mainly expressed in rosette basal region and leaf petiole and its expression was up-regulated by P-deficiency. Tissue-specific analysis showed that AtSPDT was mainly located at the vascular cambium of different organs, as well as in the parenchyma tissues of both xylem and phloem region. Knockout of this gene inhibited the growth of new leaves under low P due to decreased P distribution to those organs. The seed yield was similar between mutant lines and wild type, but the mutant lines contained 8.2%-33.6% less P in seeds. These results indicate that AtSPDT localized at the vascular cambium is involved in the preferential distribution of P to the developing tissues through the xylem-to-phloem transfer mainly in rosette basal region and leaf petiole.