Fujian Provincial Key Laboratory of Agroecological Processing and Safety Monitoring, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, People's Republic of China.
Key Laboratory of Crop Ecology and Molecular Physiology (Fujian Agriculture and Forestry University), Fujian Province Universities, Fuzhou, 350002, People's Republic of China.
Planta. 2022 Jul 16;256(2):42. doi: 10.1007/s00425-022-03952-w.
Phosphate deficiency promotes anthocyanin accumulation in Arabidopsis through direct binding of PHR1 to the P1BS motifs on the promoters of F3'H and LDOX and thereby upregulating their expression. Phosphorus is one of the essential elements for plants, and plants mainly absorb inorganic phosphate (Pi) from soil. But Pi deficiency is a common factor limiting plant growth and development. Anthocyanin accumulation in green tissues (such as leaves) is one of the characteristics of many plants in response to Pi starvation. However, little is known about the mechanism by which Pi starvation induces anthocyanin accumulation. Here, we found that the mutation of the gene PHOSPHATE STARVATION RESPONSE1 (PHR1), which encodes a key factor involved in Pi starvation signaling in Arabidopsis, significantly attenuates anthocyanin accumulation under Pi-limiting conditions. Moreover, the expression of several Pi deficiency-upregulated genes that are involved in anthocyanin biosyntheses, such as flavanone 3'-hydroxylase (F3'H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX), and production of anthocyanin pigment 1 (PAP1), was significantly lower in the phr1-1 mutant than in the wild type (WT). Both yeast one-hybrid (Y1H) analysis and chromatin immunoprecipitation quantitative PCR (ChIP-qPCR) showed that PHR1 can interact with the promoters of F3'H and LDOX, but not DFR and PAP1. By electrophoretic mobility shift assay (EMSA), it was further confirmed that the PHR1-binding sequence (P1BS) motifs located on the F3'H and LDOX promoters are required for the PHR1 bindings. Also, in Arabidopsis protoplasts, PHR1 enhanced the transcriptional activity of the F3'H and LDOX promoters, but these effects were markedly impaired when the P1BS motifs were mutated. Taken together, these results indicate that PHR1 positively regulates Pi starvation-induced anthocyanin accumulation in Arabidopsis, at least in part, by directly binding the P1BS motifs located on the promoters to upregulate the transcription of anthocyanin biosynthetic genes F3'H and LDOX.
缺磷通过 PHR1 直接结合到 F3'H 和 LDOX 启动子上的 P1BS 基序，从而上调它们的表达，促进拟南芥中花色素苷的积累。磷是植物必需的元素之一，植物主要从土壤中吸收无机磷（Pi）。但是，Pi 缺乏是限制植物生长和发育的常见因素。绿色组织（如叶片）中花色素苷的积累是许多植物对 Pi 饥饿反应的特征之一。然而，对于 Pi 饥饿如何诱导花色素苷积累的机制知之甚少。在这里，我们发现拟南芥中参与 Pi 饥饿信号转导的关键因子 PHOSPHATE STARVATION RESPONSE1（PHR1）基因突变显著削弱了在 Pi 限制条件下花色素苷的积累。此外，几个参与花色素苷生物合成的 Pi 缺乏上调基因的表达，如类黄酮 3'-羟化酶（F3'H）、二氢黄酮醇 4-还原酶（DFR）、查尔酮合成酶（CHS）、查尔酮异构酶（CHI）、二氢黄酮醇 4-还原酶（DFR）、leucoanthocyanidin dioxygenase（LDOX）和花色素苷合成酶 1（PAP1）的表达在 phr1-1 突变体中明显低于野生型（WT）。酵母单杂交（Y1H）分析和染色质免疫沉淀定量 PCR（ChIP-qPCR）表明 PHR1 可以与 F3'H 和 LDOX 启动子相互作用，但不能与 DFR 和 PAP1 相互作用。通过电泳迁移率变动分析（EMSA）进一步证实，位于 F3'H 和 LDOX 启动子上的 PHR1 结合序列（P1BS）基序是 PHR1 结合所必需的。此外，在拟南芥原生质体中，PHR1 增强了 F3'H 和 LDOX 启动子的转录活性，但当 P1BS 基序发生突变时，这些效应明显受损。综上所述，这些结果表明 PHR1 通过直接结合位于启动子上的 P1BS 基序，正调控拟南芥中 Pi 饥饿诱导的花色素苷积累，至少部分上调花色素苷生物合成基因 F3'H 和 LDOX 的转录。
