Department of Agronomy and Plant Genetics, University of Minnesota, St Paul, MN 55108, USA.
Mol Plant. 2010 Mar;3(2):428-37. doi: 10.1093/mp/ssq008. Epub 2010 Feb 10.
Shoot-to-root communication is crucial for plant acclimation to phosphorus (P)-deficiency. Both sugars and miRNAs have been implicated as potential signal molecules transported through phloem from shoot to root for the regulation of gene expression and Pi uptake in the root. By studying the expression patterns of both a serine/threonine phosphatase gene (PvHAD1) and microRNA399 (miR399) in common bean (Phaseolus vulgaris L.), we provide evidence for the interaction between light, phloem transport, and miR399 in the systemic regulation of gene expression under P-deficiency. Especially, miR399 expression in both the shoot and the root requires photosynthetic carbon assimilation during the onset of P-deficiency. In contrast to systemic signaling, local sensing was the primary causal factor for rapid down-regulation of PvHAD1 by Pi prior to the reduction of miR399 level in P-deficient roots. Furthermore, this initial response to Pi in P-deficient root was also mimicked by the Pi analog, phosphonate (Phi). Our current findings suggest that plants have developed a highly coordinated dual regulatory pathway, namely long-distance signaling of P-deficiency from shoot to root versus local sensing of Pi in the root.
根到梢的通讯对于植物适应磷（P）缺乏至关重要。糖和 miRNA 都被认为是潜在的信号分子，可以通过韧皮部从梢运输到根，调节根中的基因表达和 Pi 吸收。通过研究普通豆（Phaseolus vulgaris L.）中丝氨酸/苏氨酸磷酸酶基因（PvHAD1）和 microRNA399（miR399）的表达模式，我们为光、韧皮部运输和 miR399 在 P 缺乏下系统调节基因表达之间的相互作用提供了证据。特别是，miR399 在 P 缺乏时在梢和根中的表达都需要光合作用碳同化。与系统信号不同，局部感应是 P 缺乏根中 PvHAD1 快速下调的主要因果因素，而 miR399 水平在 P 缺乏根中的降低之前。此外，Pi 类似物膦酸盐（Phi）也模拟了 P 缺乏根中对 Pi 的这种初始反应。我们目前的发现表明，植物已经形成了一种高度协调的双重调控途径，即从梢到根的 P 缺乏的远距离信号转导与根中 Pi 的局部感应。
