Core tips: Recently, Molecular Plant, an international journal, published online the latest research results collaborated by the plant nutritional biology team from Resources & Environment College of HZAU and Ma Jianfeng's team from the Okayama University Institute of Plant Science and Resources. The research revealed a distinct mechanism for the preferential distribution of mineral nutrients to the developing tissues in dicots through detailed functional analysis of Phosphorus AtSPDT, which gave a new insight into the distribution mechanism for mineral elements.
On October 10, Molecular Plant published online a research paper entitled "Vascular cambium-localized AtSPDT mediates xylem-to-phloem transfer of phosphorus for its preferential distribution in Arabidopsis". The study revealed a mechanism for the preferential distribution of Phosphorus located at the vascular cambium of dicots. The co-first authors of this paper are Vice Prof. Ding Guangda from Resources & Environment College of HZAU and Doctor Lei Guijie from the Okayama University Institute of Plant Science and Resources. Prof. Ma Jianfeng, also from the Institute of Plant Science and Resources, is the corresponding author.
Phosphorus (P) is an essential nutrient element for plant growth and development. The researchers found that AtSPDT/AtSULTR3;4 (SULTR-like P Distribution Transporter) mediates xylem-to-phloem transfer of P for its preferential distribution to developing tissues. To examine transport activity of AtSPDT for Pi , the cRNA of AtSPDT was injected into Xenopus oocytes. The results indicated that AtSPDT was a transporter for Pi with high affinity. However, the transport activity for sulfate was not detected. At the vegetative growth stage, AtSPDT was mainly expressed in the rosette basal region and petioles. The expression was significantly up-regulated by P-deficiency. As for the reproductive growth stage, the expression of AtSPDT was detected in all organs with a relatively higher expression level in rosette basal region, nodes and silique. To investigate the tissue and cell specificity of AtSPDT expression, the researchers generated transgenic Arabidopsis lines carrying 2.2 kb promoter region of AtSPDT fused with GFP, showing that AtSPDT was mainly expressed in vascular cambium, xylem parenchyma tissue and phloem parenchyma tissue. 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. At the same time, the P concentration in xylem sap of mutant increased significantly, suggesting that AtSPDT is not involved in the distribution of other mineral elements or P redistribution. Based on the above results, they constructed a model of the preferential distribution of P in Arabidopsis. This study revealed the mechanism of xylem-to-phloem transfer of P for its preferential distribution to developing tissues in dicots. After more documents analysis，the authors believe that this mechanism may be universal for mineral nutrients distribution in dicots, which is a research result of great significance.
Translated by Gan Liuqing
Proofread by Xie Lujie