Chloroplast phosphate transporter DoPHT2;1 maintains phosphate and sucrose homeostasis in Dendrobium officinale Kimura et Migo

Dendrobium officinale Kimuraet et Migo (D. officinale) was included in the list of homology of medicine and food. The main active substances of D. officinale is polysaccharides (DOP), and the sucrose is the raw materials for DOP synthesis. Therefore, exploring the environmental factors affecting sucrose synthesis will provide important support for revealing the formation rules of D. officinale quality. We found phosphorus content was significantly correlated with sucrose metabolism. We performed WGCNA analysis and found a chloroplasts localized phosphate transporter protein DoPHT2;1. The expression of DoPHT2;1 is highly correlated with sucrose metabolism genes by transcriptome data analysis. Overexpression of DoPHT2;1 in A.thaliana and D. officinale protocorm-like bodies promote the accumulation of sucrose. Furthermore, Y1H and EMSA showed the low-phosphorus response transcription factor WRKY70 can bind the promoter cis-acting element of DoPHT2;1. We conclude that DoPHT2;1 is responsible for phosphorus transport in chloroplasts and for maintaining sucrose balance.铁皮石斛（Dendrobium officinale Kimura et Migo，以下简称D. officinale）被列入药食同源名录。其主要活性成分为多糖（DOP），蔗糖是其合成DOP的原料。因此，探究影响蔗糖合成的环境因子，可为揭示铁皮石斛品质形成规律提供重要支撑。本研究发现，磷含量与蔗糖代谢过程显著相关。通过WGCNA分析，我们成功鉴定得到定位于叶绿体的磷酸盐转运蛋白DoPHT2;1。转录组数据分析显示，DoPHT2;1的表达水平与蔗糖代谢相关基因呈高度相关性。在拟南芥（A.thaliana）和铁皮石斛原球茎中过表达DoPHT2;1，均可促进蔗糖积累。此外，通过酵母单杂交（Y1H）与电泳迁移率变动分析（EMSA）实验证实，低磷响应转录因子WRKY70能够结合DoPHT2;1的启动子顺式作用元件。本研究最终证实，DoPHT2;1兼具叶绿体磷转运与维持蔗糖平衡的双重功能。