Strigolactones affect the yield of Tartary buckwheat by regulating endogenous hormone levels.

BACKGROUND: As a newly class of endogenous phytohormones, strigolactones (SLs) regulate crop growth and yield formation by interacting with other hormones. However, the physiological mechanism of SLs affect the yield by regulating the balance of endogenous hormones of Tartary buckwheat is still unclear. RESULTS: In this study, a 2-year field experiment was conducted on Tartary buckwheat (Jinqiao 2) to study the effects of different concentrations (0, 10, and 20 µmol/L) of artificial synthetic analogs of SLs (rac-GR24) and inhibitor of SL synthesis (Tis-108) on the growth, endogenous-hormone content, and yield of Tartary buckwheat. The main-stem branch number, grain number per plant, grain weight per plant, and yield of Tartary buckwheat continuously decreased with increased rac-GR24 concentration, whereas the main-stem diameter and plant height initially increased and then decreased. Rac-GR24 treatment significantly increased the content of SLs and abscisic acid (ABA) in grains, and it decreased the content of Zeatin (Z) + Zeatin nucleoside (ZR). Conversely, Tis-108 treatment decreased the content of SLs and ABA but increased the content of Z + ZR. Results of correlation analysis showed that the content of ABA and SLs, the ratio of SLs/(Z + ZR), SLs/ABA, and ABA/(Z + ZR) were significantly negatively correlated with the yield of Tartary buckwheat, and that Z + ZR content was significantly positively correlated with the yield. Regression analysis further showed that ABA/ (Z + ZR) can explain 58.4% of the variation in yield. CONCLUSIONS: In summary, by adjusting the level of endogenous SLs in Tartary buckwheat, the balance of endogenous hormones in grains can be changed, thereby exerting the effect on yield. The results can provide a new agronomic method for the high-yield cultivation of Tartary buckwheat.

Proteomics characterization nitrogen fertilizer promotes the starch synthesis and metabolism and amino acid biosynthesis in common buckwheat.

Nitrogen (N) affects common buckwheat quality by affecting starch and amino acids (AAs) content, but its molecular mechanism is still unclear. We selected two common buckwheat varieties with high and low starch content, and designed two treatments with 180 and 0 kg N/ha. Application of high-N led to significant increases in starch, amylose and amylopectin content. Of 1337 differentially expressed proteins (DEPs) induced by high-N conditions. 472DEPs were significantly upregulated and 176DEPs downregulated for Xinong9976. 239DEPs were significantly upregulated and 126DEPs downregulated for Beizaosheng. The six alpha-glucan phosphorylases, three alpha-amylases, one granule-bound starch synthase 1 and one sucrose synthase exhibited higher expression at the 180 kg N/ha than at the 0 kg N/ha. In addition, high-N application promoted arginine, leucine, isoleucine and valine biosynthesis. This study revealed the effect of N on the starch and AA content of common buckwheat and its mechanism. The crucial proteins identified may develop the quality of common buckwheat.

The response of tartary buckwheat and 19 bZIP genes to abscisic acid (ABA).

Tartary buckwheat is a kind of plant which can be used as medicine as well as edible. Abscisic acid (ABA) signaling plays an important role in the response of plants such as tartary buckwheat to drought and other stress. However, there are not many studies on tartary buckwheat by ABA treatment. In this study, the germination, root length, stoma, and anthocyanin accumulation of tartary buckwheat were all significantly affected by ABA. ABA signaling is important for plants to respond to drought and other stresses, the bZIP gene family is an important member of the ABA signaling pathway. Through the analysis of the origin relationship between tartary buckwheat bZIP family and its related species, 19 bZIP genes in tartary buckwheat were found to be relatively conserved, which laid a foundation for further study of bZIP family. The qRT-PCR results showed that most of the group members were induced by ABA treatment, including 0, 15, 30, 50, 70 µM ABA and 0, 0.5, 2, 4, 8, 16, 24 h ABA treatment. These results suggested that ABA could affect the growth and development of tartary buckwheat, and FtbZIPs might have different functions in the response of tartary buckwheat to drought. This study will be helpful to further analyze the genetic breeding and economic value of tartary buckwheat resistance.

Elevated Ozone Levels Affect Metabolites and Related Biosynthetic Genes in Tartary Buckwheat.

Global climate change and the industrial revolution have increased the concentration of tropospheric ozone, a photochemical air pollutant that can negatively affect plant growth and crop production. In the present study, we investigated the effects of O3 on the metabolites and transcripts of tartary buckwheat. A total of 36 metabolites were identified by gas chromatography coupled with time-of-flight mass spectrometry, and principal component analysis was performed to verify the metabolic differences between nontreated and O3-treated tartary buckwheat. The content of threonic acid increased after 2 days of the O3 treatment, whereas it decreased after 4 days of exposure, after which it gradually increased until the eighth day of exposure. In addition, the levels of most metabolites decreased significantly after the O3 treatment. On the contrary, the levels of two anthocyanins, cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside, increased more than 11.36- and 11.43-fold, respectively, after the O3 treatment. To assess the effect of O3 on the genomic level, we analyzed the expression of anthocyanin biosynthesis pathway genes in O3-treated and nontreated buckwheat using quantitative real-time reverse transcription polymerase chain reaction (PCR). We found that the expression of all anthocyanin pathway genes increased significantly in the O3-treated buckwheat compared to that in the nontreated buckwheat. Altogether, our results suggested that O3 affected the transcripts and metabolites of tartary buckwheat, which would eventually cause phenotypic changes in plants.

Genome-wide analyses reveals a glucosyltransferase involved in rutin and emodin glucoside biosynthesis in tartary buckwheat.

With people's increasing needs for health concern, rutin and emodin in tartary buckwheat have attracted much attention for their antioxidant, anti-diabetic and reducing weight function. However, the biosynthesis of rutin and emodin in tartary buckwheat is still unclear; especially their later glycosylation contributing to make them more stable and soluble is uncovered. Based on tartary buckwheat' genome, the gene structures of 106 UGTs were analyzed; 21 candidate FtUGTs were selected to enzymatic test by comparing their transcript patterns. Among them, FtUGT73BE5 and other 4 FtUGTs were identified to glucosylate flavonol or emodin in vitro; especially rFtUGT73BE5 could catalyze the glucosylation of all tested flavonoids and emodin. Furthermore, the identical in vivo functions of FtUGT73BE5 were demonstrated in tartary buckwheat hairy roots. The transcript profile of FtUGT73BE5 was consistent with the accumulation trend of rutin in plant; this gene may relate to anti-adversity for its transcripts were up-regulated by MeJA, and repressed by ABA.

Transcriptome profiling of Fagopyrum tataricum leaves in response to lead stress.

BACKGROUND: Lead (Pb) pollution is a widespread environmental problem that is harmful to living organisms. Tartary buckwheat (Fagopyrum tataricum), a member of the family Polygonaceae, exhibits short growth cycles and abundant biomass production, could be an ideal plant for phytoremediation due to its high Pb tolerance. Here, we aimed to explore the molecular basis underlying the responses of this plant to Pb stress. RESULTS: In our study, ultrastructural localization assays revealed that Pb ions primarily accumulate in leaf vacuoles. RNA deep sequencing (RNA-Seq) of tartary buckwheat leaves was performed on two Pb-treated samples, named Pb1 (2000 mg/kg Pb (NO3)2) and Pb2 (10,000 mg/kg Pb (NO3)2), and a control (CK). A total of 88,977 assembled unigenes with 125,203,555 bases were obtained. In total, 2400 up-regulated and 3413 down-regulated differentially expressed genes (DEGs) were identified between CK and Pb1, and 2948 up-regulated DEGs and 3834 down-regulated DEGs were generated between CK and Pb2, respectively. Gene Ontology (GO) and pathway enrichment analyses showed that these DEGs were primarily associated with 'cell wall', 'binding', 'transport', and 'lipid and energy' metabolism. The results of quantitative real-time PCR (qRT-PCR) analyses of 15 randomly selected candidate DEGs and 6 regulated genes were consistent with the results of the transcriptome analysis. Heterologous expression assays in the yeast strain Δycf1 indicated that overexpressing CCCH-type zinc finger protein 14 (ZFP14) enhanced sensitivity to Pb2+, while 5 other genes, namely, metal transporter protein C2 (MTPC2), phytochelatin synthetase-like family protein (PCSL), vacuolar cation/proton exchanger 1a (VCE1a), natural resistance-associated macrophage protein 3 (Nramp3), and phytochelatin synthetase (PCS), enhanced the Pb tolerance of the mutant strain. CONCLUSION: Combining our findings with those of previous studies, we generated a schematic model that shows the metabolic processes of tartary buckwheat under Pb stress. This study provides important data for further genomic analyses of the biological and molecular mechanisms of Pb tolerance and accumulation in tartary buckwheat.

Effect of calcium chloride and sucrose on the composition of bioactive compounds and antioxidant activities in buckwheat sprouts.

In this study, we evaluated the effect of sucrose and CaCl2 on the growth profile, nutritional quality, and antioxidant capacity of sprouted buckwheat. Buckwheat seeds were germinated at 25 °C for 8 days and sprayed with four different solutions: distilled water, 3% sucrose, 7.5 mM CaCl2, and 3% sucrose plus 7.5 mM CaCl2. Our results showed that CaCl2 effectively improved sucrose-elicitation induced growth reduction in buckwheat sprouts. Elicitation with both sucrose and CaCl2 in buckwheat sprouts markedly enhanced the accumulation of bioactive compounds, such as polyphenols, flavonoids, γ-aminobutyric acid, vitamin C, and E, without negatively affecting sprout growth. Elicitation with both sucrose and CaCl2 not only significantly enhanced the antioxidant activities but also exerted cytoprotective effects against oxidative damage in HepG2 cells and fibroblasts. These findings suggested that simultaneous elicitation with 3% sucrose and 7.5 mM CaCl2 can potentially improve the nutritional value and potential health benefits of buckwheat sprouts.

Examining a synchrotron-based approach for in situ analyses of Al speciation in plant roots.

Aluminium (Al) K- and L-edge X-ray absorption near-edge structure (XANES) has been used to examine Al speciation in minerals but it remains unclear whether it is suitable for in situ analyses of Al speciation within plants. The XANES analyses for nine standard compounds and root tissues from soybean (Glycine max), buckwheat (Fagopyrum tataricum), and Arabidopsis (Arabidopsis thaliana) were conducted in situ. It was found that K-edge XANES is suitable for differentiating between tetrahedral coordination (peak of 1566 eV) and octahedral coordination (peak of 1568 to 1571 eV) Al, but not suitable for separating Al binding to some of the common physiologically relevant compounds in plant tissues. The Al L-edge XANES, which is more sensitive to changes in the chemical environment, was then examined. However, the poorer detection limit for analyses prevented differentiation of the Al forms in the plant tissues because of their comparatively low Al concentration. Where forms of Al differ markedly, K-edge analyses are likely to be of value for the examination of Al speciation in plant tissues. However, the apparent inability of Al K-edge XANES to differentiate between some of the physiologically relevant forms of Al may potentially limit its application within plant tissues, as does the poorer sensitivity at the L-edge.

Effects of phosphate fertiliser on the physicochemical properties of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) starch.

Phosphate fertilisation affects the growth, development and quality of Tartary buckwheat. In this study, the effect of different phosphorus levels, including 0, 15, 75, and 135 kg/ha (non-, low-, medium-, and high-phosphorus levels, respectively), on the characteristics of starch from Tartary buckwheat were investigated in 2015 and 2017. With increased phosphorus level, the median diameter of starch granules and the apparent amylose content initially decreased and then increased. All starch samples showed the features of A-type X-ray diffraction patterns. Starches under medium-phosphorus treatment showed higher relative crystallinity than those under non-phosphorus treatment, as well as the highest solubility, gelatinisation enthalpy and transmittance among all starches. Starches under low-phosphorus treatment exhibited higher pasting properties than those under non-phosphorus treatment. This research revealed that phosphorus treatments and year significantly affected the physicochemical properties of Tartary buckwheat starch, and can provide information for the applications of starch in the food and non-food industries.

Effects of exogenous sulfur on alleviating cadmium stress in tartary buckwheat.

Supplying exogenous sulfur-rich compounds increases the content of glutathione(GSH) and phytochelatins(PCs) in plant tissues, enabling plants to enhance their cellular defense capacity and/or compartmentalize Cadmium(Cd) into vacuoles. However, the mechanism by which surplus S modulates tolerance to Cd stress in different tissues need further investigation. In the present study, we found that supplementing the tartary buckwheat(Fagopyrum tararicum) exposed to Cd with surplus S reversed Cd induced adverse effects, and increased Cd concentrations in roots, but decreased in leaves. Further analysis revealed that exogenous S significantly mitigated Cd-induced oxidative stress with the aids of antioxidant enzymes and agents both in leaves and roots, including peroxidase(POD), ascorbate peroxidase(APX), glutathione peroxidase(GPX), glutathione S-transferase(GST), ascorbic acid(AsA), and GSH, but not superoxide dismutase(SOD) and catalase(CAT). The increased Cd uptake in root vacuoles and decreased translocation in leaves of exogenous S treated plants could be ascribed to the increasing Cd binding on cell walls, chelation and vacuolar sequestration with helps of non-protein thiols(NPT), PCs and heavy metal ATPase 3(FtHMA3) in roots, and inhibiting expression of FtHMA2, a transporter that helps Cd translocation from roots to shoots. Results provide the fundamental information for the application of exogenous S in reversal of heavy metal stress.

Antioxidative defense mechanism against lead-induced phytotoxicity in Fagopyrum kashmirianum.

The effect of lead (Pb)-induced oxidative stress was investigated in Fagopyrum kashmirianum. The seedlings absorbed the Pb readily by showing time (15 and 30 days) and concentration (0, 100, 200 and 300 µM) dependent effects. Pb caused reduction in both root and shoot lengths but its accumulation was more in roots (22.32 mg g-1 DW) than shoots (8.86 mg g-1 DW) at the highest concentration (300 µM) resulting in translocation factor (TF) < 1 at all concentrations. Thus the uptake and translocation of Pb between roots and shoots showed a positive correlation indicating the plant as root accumulator. Amongst the photosynthetic pigments, chlorophyll content showed a decline while the carotenoid and anthocyanin levels were elevated. The fresh mass and biomass showed a non-significant decrease at both the sampling times. The osmolyte and antioxidative enzymes (SOD, CAT, APX. POD, GR and GST) were positively correlated with Pb treatments except proline and CAT, which showed decline in 30-day-old plants. The alleviation of Pb-stress is an indication for existence of strong detoxification mechanism in F. kashmirianum, which suggest that it could be cultivated in Pb-contaminated soils.

Genome-Wide Investigation of the Auxin Response Factor Gene Family in Tartary Buckwheat (Fagopyrum tataricum).

Auxin signaling plays an important role in plant growth and development. It responds to various developmental and environmental events, such as embryogenesis, organogenesis, shoot elongation, tropical growth, lateral root formation, flower and fruit development, tissue and organ architecture, and vascular differentiation. However, there has been little research on the Auxin Response Factor (ARF) genes of tartary buckwheat (Fagopyrum tataricum), an important edible and medicinal crop. The recent publication of the whole-genome sequence of tartary buckwheat enables us to study the tissue and expression profile of the FtARF gene on a genome-wide basis. In this study, 20 ARF (FtARF) genes were identified and renamed according to the chromosomal distribution of the FtARF genes. The results showed that the FtARF genes belonged to the related sister pair, and the chromosomal map showed that the duplication of FtARFs was related to the duplication of the chromosome blocks. The duplication of some FtARF genes shows conserved intron/exon structure, which is different from other genes, suggesting that the function of these genes may be diverse. Real-time quantitative PCR analysis exhibited distinct expression patterns of FtARF genes in various tissues and in response to exogenous auxin during fruit development. In this study, 20 FtARF genes were identified, and the structure, evolution, and expression patterns of the proteins were studied. This systematic analysis laid a foundation for the further study of the functional characteristics of the ARF genes and for the improvement of tartary buckwheat crops.

A R2R3-MYB transcription factor gene, FtMYB13, from Tartary buckwheat improves salt/drought tolerance in Arabidopsis.

Abiotic stress causes various negative impacts on plants, such as water loss, reactive oxygen species (ROS) accumulation and decreased photosynthesis. R2R3-MYB transcription factors (TFs) play crucial roles in the response of plants to abiotic stress. However, their functions in Tartary buckwheat, a strongly abiotic and resistant coarse cereal, haven't been fully investigated. In this paper, we report that a R2R3-MYB from Tartary buckwheat, FtMYB13, is not an activator of transcriptional activity but is located in the nucleus. Moreover, compared to the wild type (WT), transgenic Arabidopsis overexpressing FtMYB13 had a lower sensitivity to ABA and caused improved drought/salt tolerance, which was attributed to the higher proline content, greater photosynthetic efficiency, higher transcript abundance of some stress-related genes and the smaller amount of reactive oxygen species (ROS) and malondialdehyde (MDA) in the transgenic lines compared to WT. Consequently, our work indicates that FtMYB13 is involved in mediating plant responses to ABA, as well as salt and drought.

Two Genes Encoding a Bacterial-Type ATP-Binding Cassette Transporter are Implicated in Aluminum Tolerance in Buckwheat.

Buckwheat (Fagopyrum esculentum Moench) shows high tolerance to aluminum (Al) toxicity, but the molecular mechanisms underlying its high Al tolerance are poorly understood. Here, we functionally characterized two genes (FeSTAR1 and FeSTAR2), which encode a nucleotide-binding domain and a membrane domain, respectively, of a bacterial-type ATP-binding cassette (ABC) transporter. The expression of FeSTAR1 and FeSTAR2 was induced by Al in both roots and leaves with higher expression in the roots. Spatial and tissue-specific expression analysis showed that the Al-induced expression of these two genes was found in both the root tips and basal root regions with higher expression in the root outer cell layers. The expression was neither induced by other metals including Cd and La nor by low pH and phosphorus-deficiency. FeSTAR1 and FeSTAR2 were present in a single copy in the genome, but the Al-induced transcript copy number of FeSTAR1 and FeSTAR2 was much higher than their homologous genes in rice and Arabidopsis. FeSTAR1 and FeSTAR2 form a complex when co-expressed in onion epidermal cells. Introduction of FeSTAR1 and FeSTAR2 into Arabidopsis mutants atstar1 and als3/atstar2, respectively, rescued the sensitivity of the mutants to Al. Taken together, our results indicate that FeSTAR1 and FeSTAR2 are involved in Al tolerance and that their high expression level may contribute to high Al tolerance in buckwheat.

Phytotoxicity of polymetallic mine wastes from southern Tuscany and Saxony.

Restoration potential of mine wastes or approaches to improve soil conditions and to ameliorate phytotoxicity on these sites may be simulated in standardized greenhouse experiments. Plants can be cultivated side by side on materials from different origins in dilution series with defined admixtures of certain aggregates. Mine wastes used in the present study originated from Fenice Capanne (FC, Tuscany, Italy) and Altenberg (ALT, Saxony, Germany). Tailings of the Italian site contain high concentrations of lead, zinc, arsenic and sulphur while tin, wolfram, molybdenum and lithium are highly elevated in the German mine waste. We tested growth responses of five crop species and analyzed concentrations of various metals and nutrients in the shoot to evaluate the toxicity of the FC mine waste and found oilseed rape being the most and corn the least resistant crop. Interestingly, oilseed rape accumulated seven times higher levels of lead than corn without showing adverse effects on productivity. In a subsequent comparison of FC and ALT mine waste, we cultivated different species of buckwheat (Fagopyrum spec.), a fast growing genus that evolved in mountain areas and that has been shown to be tolerant to low pH and high concentrations of metals. We found that the FC mine waste was more toxic than the ALT substrate in F. tataricum and F. esculentum. However, lower admixtures of FC material (10%) resulted in stronger growth reductions than higher proportions (25%) of the mine waste which was primarily related to the slightly lower pH and higher availability of essential metals due to the admixture of sand. These results confirm the importance of managing the soil chemical and physical characteristics of wastelands and call for the development of assisted reclamation to prepare sites for regular biomass production.

Calcium oxalate druses affect leaf optical properties in selenium-treated Fagopyrum tataricum.

Plants of the genus Fagopyrum contain high levels of crystalline calcium oxalate (CaOx) deposits, or druses, that can affect the leaf optical properties. As selenium has been shown to modify the uptake and accumulation of metabolically important elements such as calcium, we hypothesised that the numbers of druses can be altered by selenium treatment, and this would affect the leaf optical properties. Tartary buckwheat (Fagopyrum tataricum Gaertn.) was grown outdoors in an experimental field. At the beginning of flowering, plants were foliarly sprayed with sodium selenate solution at 10 mg selenium L-1 or only with water. Plant morphological, biochemical, physiological and optical properties were examined, along with leaf elemental composition and content. Se spraying did not affect leaf biochemical and functional properties. However, it increased leaf thickness and the contents of Se in the leaves, and decreased the density of calcium oxalate druses in the leaves. Except Se content, Se spraying did not affect contents of other elements in leaves, including total calcium per dry mass of leaf tissue. Redundancy analysis showed that of all parameters tested, only the calcium oxalate druses parameters were significant in explaining the variability of the leaf reflectance and transmittance spectra. The density of CaOx druses positively correlated with the reflectance in the blue, green, yellow and UV-B regions of the spectrum, while the area of CaOx druses per mm2 of leaf transection area positively correlated with the transmittance in the green and yellow regions of the spectrum.

Two MATE Transporters with Different Subcellular Localization are Involved in Al Tolerance in Buckwheat.

Buckwheat (Fagopyrum esculentum) shows high tolerance to aluminum (Al) toxicity, but the molecular mechanisms responsible for this high Al tolerance are still poorly understood. Here, we investigated the involvement of two MATE (multi-drug and toxic compound extrusion) genes in Al tolerance. Both FeMATE1 and FeMATE2 showed efflux transport activity for citrate, but not for oxalate when expressed in Xenopus oocytes. A transient assay with buckwheat leaf protoplasts using green fluorescent protein (GFP) fusion showed that FeMATE1 was mainly localized to the plasma membrane, whereas FeMATE2 was localized to the trans-Golgi and Golgi. The expression of FeMATE1 was induced by Al only in the roots, but that of FeMATE2 was up-regulated in both the roots and leaves. Furthermore, the expression of both genes only responded to Al toxicity, but not to other stresses including low pH, cadmium (Cd) and lanthanum (La). Heterologous expression of FeMATE1 or FeMATE2 in the Arabidopsis mutant atmate partially rescued its Al tolerance. Expression of FeMATE1 also partially recovered the Al-induced secretion of citrate in the transgenic lines, whereas expression of FeMATE2 did not complement the citrate secretion. Further physiological analysis showed that buckwheat roots also secreted citrate in addition to oxalate in response to Al in a dose-responsive manner. Taken together, our results indicate that FeMATE1 is involved in the Al-activated citrate secretion in the roots, while FeMATE2 is probably responsible for transporting citrate into the Golgi system for the internal detoxification of Al in the roots and leaves of buckwheat.

The Tartary Buckwheat Genome Provides Insights into Rutin Biosynthesis and Abiotic Stress Tolerance.

Tartary buckwheat (Fagopyrum tataricum) is an important pseudocereal crop that is strongly adapted to growth in adverse environments. Its gluten-free grain contains complete proteins with a well-balanced composition of essential amino acids and is a rich source of beneficial phytochemicals that provide significant health benefits. Here, we report a high-quality, chromosome-scale Tartary buckwheat genome sequence of 489.3 Mb that is assembled by combining whole-genome shotgun sequencing of both Illumina short reads and single-molecule real-time long reads, sequence tags of a large DNA insert fosmid library, Hi-C sequencing data, and BioNano genome maps. We annotated 33 366 high-confidence protein-coding genes based on expression evidence. Comparisons of the intra-genome with the sugar beet genome revealed an independent whole-genome duplication that occurred in the buckwheat lineage after they diverged from the common ancestor, which was not shared with rosids or asterids. The reference genome facilitated the identification of many new genes predicted to be involved in rutin biosynthesis and regulation, aluminum stress resistance, and in drought and cold stress responses. Our data suggest that Tartary buckwheat's ability to tolerate high levels of abiotic stress is attributed to the expansion of several gene families involved in signal transduction, gene regulation, and membrane transport. The availability of these genomic resources will facilitate the discovery of agronomically and nutritionally important genes and genetic improvement of Tartary buckwheat.

Genome-Wide Transcriptome Analysis Reveals Conserved and Distinct Molecular Mechanisms of Al Resistance in Buckwheat (Fagopyrum esculentum Moench) Leaves.

Being an Al-accumulating crop, buckwheat detoxifies and tolerates Al not only in roots but also in leaves. While much progress has recently been made toward Al toxicity and resistance mechanisms in roots, little is known about the molecular basis responsible for detoxification and tolerance processes in leaves. Here, we carried out transcriptome analysis of buckwheat leaves in response to Al stress (20 µM, 24 h). We obtained 33,931 unigenes with 26,300 unigenes annotated in the NCBI database, and identified 1063 upregulated and 944 downregulated genes under Al stress. Functional category analysis revealed that genes related to protein translation, processing, degradation and metabolism comprised the biological processes most affected by Al, suggesting that buckwheat leaves maintain flexibility under Al stress by rapidly reprogramming their physiology and metabolism. Analysis of genes related to transcription regulation revealed that a large proportion of chromatin-regulation genes are specifically downregulated by Al stress, whereas transcription factor genes are overwhelmingly upregulated. Furthermore, we identified 78 upregulated and 22 downregulated genes that encode transporters. Intriguingly, only a few genes were overlapped with root Al-regulated transporter genes, which include homologs of AtMATE, ALS1, STAR1, ALS3 and a divalent ion symporter. In addition, we identified a subset of genes involved in development, in which genes associated with flowering regulation were important. Based on these data, it is proposed that buckwheat leaves develop conserved and distinct mechanisms to cope with Al toxicity.

Overexpression of a tartary buckwheat R2R3-MYB transcription factor gene, FtMYB9, enhances tolerance to drought and salt stresses in transgenic Arabidopsis.

Tartary buckwheat (Fagopyrum tataricum) is a traditional coarse cereal that exhibits strong plasticity in its adaptation to harsh and complicated environmental stresses. In an attempt to study the strong tolerance of tartary buckwheat, the FtMYB9 gene, which encodes an R2R3-MYB transcription factor protein, was functionally investigated. FtMYB9 expression was rapidly and strongly induced by ABA, cold, salt, and drought treatments in the seedling stage. A yeast one-hybrid system assay indicated that FtMYB9 is an activator of transcriptional activity, consistent with its roles as a transcription factor. Its overexpression in plants resulted in increased sensitivity to ABA at the germination and seedling stages compared to wild type. The overexpression of FtMYB9 increased tolerance to drought and salt stresses by the activation of some stress-related genes from both ABA-independent and ABA-dependent pathways in transgenic Arabidopsis. Furthermore, enhanced proline content and the activation of the P5CS1 gene implied that FtMYB9 may be involved in proline synthesis in plants. Collectively, these results suggest that FtMYB9 functions as a novel R2R3-MYB TF which plays positive roles in salt and drought tolerance by regulating different stress-responsive signaling pathways.