During plant growth and development mineral elements are preferentially delivered to different organs and tissues to meet the differential demand. It has been shown that the preferential distribution of mineral nutrients in gramineous plants is mediated by node-based transporters, but the mechanisms of preferential distribution in dicots are poorly understood. Here, we report a distinct mechanism for the preferential distribution of phosphorus (P) in Arabidopsis plants, revealed by detailed functional analysis of AtSPDT/AtSULTR3;4 (SULTR-like P Distribution Transporter), a homolog of rice OsSPDT. Like OsSPDT, AtSPDT is localized at the plasma membrane and showed proton-dependent transport activity for P. Interestingly, we found that AtSPDT is mainly expressed in the rosette basal region and leaf petiole, and its expression is up-regulated by P deficiency. Tissue-specific analysis showed that AtSPDT is mainly located in the vascular cambium of different organs, as well as in the parenchyma tissues of both xylem and phloem regions. Knockout of AtSPDT inhibited the growth of new leaves under low P due to decreased P distribution to those organs. The seed yields of the wild-type and atspdt mutant plants are similar, but the seeds of mutant plants contain – less P. These results indicate that AtSPDT localized in the vascular cambium is involved in preferential distribution of P to the developing tissues, through xylem-to-phloem transfer mainly at the rosette basal region and leaf petiole.

在植物生长发育过程中，矿物质元素会优先输送到不同的器官和组织，以满足不同的需求。已经显示，禾本科植物中矿质养分的优先分布是由基于节的转运蛋白介导的，但双子叶植物中优先分布的机理却鲜为人知。在这里，我们报告了拟南芥植物中磷（P）优先分配的独特机制，通过对水稻OsSPDT的同源物AtSPDT / AtSULTR3; 4（SULTR-like P Distribution Transporter）的详细功能分析揭示了该机制。像OsSPDT一样，AtSPDT也位于质膜上，并表现出质子依赖的P转运活性。有趣的是，我们发现AtSPDT缺磷主要在莲座丛的基底区域和叶柄中表达，其表达上调。组织特异性分析表明，AtSPDT主要位于不同器官的血管形成层，以及木质部和韧皮部区域的薄壁组织中。在低磷条件下，AtSPDT的敲除抑制了新叶的生长，因为低磷分布在这些器官上。野生型和atspdt突变植物的种子产量相似，但是突变植物的种子含有–较少的P。这些结果表明，定位在维管形成层中的AtSPDT通过木质部参与了P向发育中组织的优先分配。到韧皮部的转移主要在莲座丛的基部区域和叶片的叶柄上进行。