Genetically controlling VACUOLAR PHOSPHATE TRANSPORTER 1 contributes to low-phosphorus seeds in Arabidopsis

Phosphorus (P) is an indispensable nutrient for seed germination, but the seeds always store excessive P over demand. High-P seeds of feeding crops lead to environmental and nutrition issues, because phytic acid (PA), the major form of P in seeds, cannot be digested by mono-gastric animals. Therefore, reduction of P level in seeds has become an imperative task in agriculture. Our study here suggested that both VPT1 and VPT3, two vacuolar phosphate transporters responsible for vacuolar Pi sequestration, were downregulated in leaves during the flowering stage, which led to less Pi accumulated in leaves and more Pi allocated to reproductive organs, and thus high-P containing seeds. To reduce the total P content in seeds, we genetically regulated VPT1 during the flowering stage and found that overexpression of VPT1 in leaves could reduce P content in seeds without affecting the production and seed vigor. Therefore, our finding provides a potential strategy to reduce the P level of the seeds to prevent the nutrition over-accumulation pollution

A vacuolar phosphate transporter essential for phosphate homeostasis in Arabidopsis

Inorganic phosphate (Pi) is stored in the vacuole, allowing plants to adapt to variable Pi availability in the soil. The transporters that mediate Pi sequestration into vacuole remain unknown, however. Here we report the functional characterization of Vacuolar Phosphate Transporter 1 (VPT1), an SPX domain protein that transports Pi into the vacuole in Arabidopsis. The vpt1 mutant plants were stunted and consistently retained less Pi than wild type plants, especially when grown in medium containing high levels of Pi. In seedlings, VPT1 was expressed primarily in younger tissues under normal conditions, but was strongly induced by high-Pi conditions in older tissues, suggesting that VPT1 functions in Pi storage in young tissues and in detoxification of high Pi in older tissues. As a result, disruption of VPT1 rendered plants hypersensitive to both low-Pi and high-Pi conditions, reducing the adaptability of plants to changing Pi availability. Patch-clamp analysis of isolated vacuoles showed that the Pi influx current was severely reduced in vpt1 compared with wild type plants. When ectopically expressed in Nicotiana benthamiana mesophyll cells, VPT1 mediates vacuolar influx of anions, including Pi, SO4(2-), NO3(-), Cl(-), and malate with Pi as that preferred anion. The VPT1-mediated Pi current amplitude was dependent on cytosolic phosphate concentration. Single-channel analysis showed that the open probability of VPT1 was increased with the increase in transtonoplast potential. We conclude that VPT1 is a transporter responsible for vacuolar Pi storage and is essential for Pi adaptation in Arabidopsis

Plant Membrane Transport Research in the Post-genomic Era

Membrane transport processes are indispensable for many aspects of plant physiology including mineral nutrition, solute storage, cell metabolism, cell signaling, osmoregulation, cell growth, and stress responses. Completion of genome sequencing in diverse plant species and the development of multiple genomic tools have marked a new era in understanding plant membrane transport at the mechanistic level. Genes coding for a galaxy of pumps, channels, and carriers that facilitate various membrane transport processes have been identified while multiple approaches are developed to dissect the physiological roles as well as to define the transport capacities of these transport systems. Furthermore, signaling networks dictating the membrane transport processes are established to fully understand the regulatory mechanisms. Here, we review recent research progress in the discovery and characterization of the components in plant membrane transport that take advantage of plant genomic resources and other experimental tools. We also provide our perspectives for future studies in the field

A vacuolar phosphate transporter essential for phosphate homeostasis in Arabidopsis

Inorganic phosphate (Pi) is stored in the vacuole, allowing plants to adapt to variable Pi availability in the soil. The transporters that mediate Pi sequestration into vacuole remain unknown, however. Here we report the functional characterization of Vacuolar Phosphate Transporter 1 (VPT1), an SPX domain protein that transports Pi into the vacuole in Arabidopsis. The vpt1 mutant plants were stunted and consistently retained less Pi than wild type plants, especially when grown in medium containing high levels of Pi. In seedlings, VPT1 was expressed primarily in younger tissues under normal conditions, but was strongly induced by high-Pi conditions in older tissues, suggesting that VPT1 functions in Pi storage in young tissues and in detoxification of high Pi in older tissues. As a result, disruption of VPT1 rendered plants hypersensitive to both low-Pi and high-Pi conditions, reducing the adaptability of plants to changing Pi availability. Patch-clamp analysis of isolated vacuoles showed that the Pi influx current was severely reduced in vpt1 compared with wild type plants. When ectopically expressed in Nicotiana benthamiana mesophyll cells, VPT1 mediates vacuolar influx of anions, including Pi, SO(4)(2−), NO(3)(−), Cl(−), and malate with Pi as that preferred anion. The VPT1-mediated Pi current amplitude was dependent on cytosolic phosphate concentration. Single-channel analysis showed that the open probability of VPT1 was increased with the increase in transtonoplast potential. We conclude that VPT1 is a transporter responsible for vacuolar Pi storage and is essential for Pi adaptation in Arabidopsis

Family-wide survey of miR169s and NF-YAs and their expression profiles response to abiotic stress in maize roots.

Previous studies have identified miR169/NF-YA modules are important regulators of plant development and stress responses. Currently, reported genome sequence data offers an opportunity for global characterization of miR169 and NF-YA genes, which may provide insights into the molecular mechanisms of the miR169/NF-YA modules in maize. In our study, fourteen NF-YA transcription factors with conserved domains were identified based on maize genome loci. The miR169 gene family has 18 members that generate 10 mature products, and 8 of these mature miR169 members could target 7 of 14 ZmNF-YA genes in maize. The seven ZmNF-YA proteins were localized to the nucleus while lacked transcriptional activity. We investigated the expression patterns of the zma-miR169 members and their targeted ZmNF-YA genes in maize roots treated by drought stress (polyethylene glycol, PEG), hormone stress (abscisic acid, ABA), and salt stress (NaCl). The zma-miR169 family members were downregulated in short term (0 ∼ 48 h) and generally upregulated over the long term (15 days) in response to the three abiotic stress conditions. Most of the targeted ZmNF-YA genes exhibited a reverse correlation with zma-miR169 gene expression over both the short term and long term. Maize root elongation was promoted by PEG and ABA but repressed by NaCl over the long term. Apparently, ZmNF-YA14 expression perfectly matched the zma-miR169 expression and corresponded to root growth reversely

Amino acid alignment of NF-YA core domains from Sc, Saccharomyces cerevisiae; At, Arabidopsis; Hs, Homo sapiens; Zm, Zea mays.

<p>Amino acid alignment of NF-YA core domains from Sc, Saccharomyces cerevisiae; At, Arabidopsis; Hs, Homo sapiens; Zm, Zea mays.</p

Maize root growth and <i>zma-miR169/ZmNF-YA14</i> module expression in response to treatment with NaCl, ABA, or PEG.

<p>(A) Root phenotypes in response to treatment with NaCl, ABA, or PEG for 15 days. (B) Root lengths of seedlings treated with NaCl, ABA, or PEG. (C) Relative expression levels of <i>zma-miR169</i> genes in seedlings treated with NaCl, ABA, or PEG. (D) Relative expression levels of <i>ZmNF-YA14</i> in seedlings treated with NaCl, ABA, or PEG.</p

Nuclear acid sequence alignments of mature zma-miR169 (A) and zma-miR169 target sites in ZmNF-YA family members (B).

<p><i>Zma-miR169d</i> and <i>zma-miR169e</i> are deleted at sequence 11.</p

Phylogenetic analyses of NF-YA proteins.

<p>(A) Phylogenetic analysis of ZmNF-YA family members. (B) Phylogenetic analysis of NF-YA proteins from maize, rice, and Arabidopsis. (C) Syntenic relationships of NF-YA genes between maize and rice. Each line represents an orthologous gene. The loci of <i>NF-YA</i> genes involved are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091369#pone.0091369.s008" target="_blank">Table S3</a>. Phylogenetic trees were constructed by neighbor joining with complete deletions as implemented by Molecular Evolutionary Genetics Analysis software, version 5.0 (MEGA5) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091369#pone.0091369-Tamura1" target="_blank">[33]</a>. Reliability values at each branch represent bootstrap samples (1000 replicates).</p