Sucrose Synthase Gene Research Articles

Transcriptome analysis reveals potential mechanisms for different grain size between natural and resynthesized allohexaploid wheats with near-identical AABB genomes

BackgroundCommon wheat is a typical allohexaploid species (AABBDD) derived from the interspecific crossing between allotetraploid wheat (AABB) and Aegilops tauschii (DD). Wide variation in grain size and shape observed among Aegilops tauschii can be retained in synthetic allohexaploid wheats, but the underlying mechanism remains enigmatic. Here, the natural and resynthesized allohexaploid wheats with near-identical AB genomes and different D genomes (TAA10 and XX329) were employed for analysis.ResultsSignificant differences in grain size and weight between TAA10 and XX329 were observed at the early stages of development, which could be mainly attributed to the higher growth rates of the pericarp and endosperm cells in XX329 compared to TAA10. Furthermore, comparative transcriptome analysis identified that 8891 of 69,711 unigenes (12.75%) were differentially expressed between grains at 6 days after pollination (DAP) of TAA10 and XX329, including 5314 up-regulated and 3577 down-regulated genes in XX329 compared to TAA10. The MapMan functional annotation and enrichment analysis revealed that the differentially expressed genes were significantly enriched in categories of cell wall, carbohydrate and hormone metabolism. Notably, consistent with the up-regulation of sucrose synthase genes in resynthesized relative to natural allohexaploid wheat, the resynthesized allohexaploid wheat accumulated much higher contents of glucose and fructose in 6-DAP grains than those of the natural allohexaploid wheat.ConclusionsThese data indicated that the genetic variation of the D genome induced drastic alterations of gene expression in grains of the natural and resynthesized allohexaploid wheats, which may contribute to the observed differences in grain size and weight.

Transcript profiling of sucrose synthase genes involved in sucrose metabolism among four carrot (Daucus carota L.) cultivars reveals distinct patterns

BackgroundCarrot which contains lots of nutrients has a large demand around the world. The soluble sugar content in fleshy root of carrot directly influences its taste and quality. Sucrose, as an important member of soluble sugar, is the main product of photosynthesis in higher plants and it plays pivotal roles in physiological processes including energy supply, signal transduction, transcriptional regulation, starch and cellulose synthesis, and stress tolerance. Sucrose synthase is a key enzyme involved in sucrose metabolism and is closely related to sucrose content. However, the molecular mechanism involved in sucrose metabolism in carrot has lagged behind.ResultsHere, carrot roots of five developmental stages from four carrot cultivars were collected, and the contents of soluble sugar and sucrose in different stages and cultivars were surveyed. Three DcSus genes (DcSus1, DcSus2, and DcSus3), with lengths of 2427 bp, 2454 bp and 2628 bp, respectively, were identified and cloned in carrot. Phylogenetic analysis from the deduced amino acid sequences suggested that three DcSus were clustered into three distinct groups (SUSI, II and III). Results of enzymatic profiles demonstrated that the DcSus activities showed decrease trends during taproot development. Correlation analysis indicated that the DcSus activity showed negative correlation with soluble sugar content and strong negative correlation with sucrose concentration. Quantitative real-time PCR analysis showed that the expression profiles of the DcSus genes are significantly different in carrot tissues (root, leaf blade, and petiole), and the expression levels of the DcSus genes in the leaf blade were much higher than that in the root and petiole. The expression profiles of DcSus genes showed strong negative correlation with both sucrose content and soluble sugar content.ConclusionsDuring carrot root development, the soluble sugar content and sucrose content showed increasing trends, while DcSus activities had persisting declinations, which may be due to the decreasing expression levels of genes encoding sucrose synthase. Our data demonstrate that synthesis of sucrose in carrot tissue is closely related with DcSus genes. The results from our study would not only provide effective insights of sucrose metabolism in carrot, but also are beneficial for biologists to improve carrot quality.

Molecular cloning and expression analysis of seven sucrose synthase genes in bamboo (Bambusa emeiensis): investigation of possible roles in the regulation of cellulose biosynthesis and response to hormones

ABSTRACTSucrose synthase (SUS, EC 2.4.1.13) is a key enzyme involved in sucrose metabolism. In this study, amplification by polymerase chain reaction confirmed that there are at least seven SUS genes (BeSUS1-7) in the Bambusa emeiensis genome. The expression patterns of the BeSUSs genes differed from each other in various bamboo tissues. Among these BeSUSs, BeSUS2 was expressed predominately in the root and BeSUS5 was most abundant in developing shoots, indicating that these two isozymes might play more important physiological roles in root and shoot than the other BeSUSs genes, respectively. In addition, BeSUSs response to abscisic acid (ABA), methyl jasmonate (MeJA) and 2,6-dichlorobenzonitrile treatment (2,6-DCB, an inhibitor of cellulose synthesis) was also investigated in leaves. The results showed that the expression levels of the BeSUS1, 5 and 7 genes were not only conspicuously induced by ABA treatment but also up-regulated by exogenous application of MeJA, indicating that these three isozymes are most likely involved in ABA and MeJA stress responses and are important in meeting the increased glycolytic demand that occurs during these stresses. Moreover, after 2,6-DCB treatment, the cellulose content of leaves was decreased and the transcripts of BeSUS2, 3 and 7 were markedly decreased, while those of BeSUS 5 and 6 were conspicuously induced. The results suggest that the possible roles of BeSUSs genes in the pathway of sucrose metabolism, bamboo resistance to abiotic stresses and the regulation of cellulose biosynthesis may be divergent.

Isolation and Analysis of Sucrose Synthase (SUS) Gene Fragment Originated from “Kopyor” Coconut Mutant

Isolation and Analysis of Sucrose Synthase (SUS) Gene Fragment Originated from “Kopyor” Coconut Mutant

Functional analysis of a grape WRKY30 gene in drought resistance

WRKY transcription factors constitute a large protein family in plants and take part in a variety of stress response processes, such as drought resistance. In this study, the drought resistant function of a WRKY transcription factor gene WRKY30 from a wine grape cultivar ‘Vidal Blanc’ was investigated. Quantitative real-time PCR (qRT-PCR) analysis indicated that the expression of VvWRKY30 was induced by drought stress and stress response related signal molecules, such as abscisic acid (ABA), nitric oxide and salicylic acid. Phenotypic analysis of transgenic Arabidopsis indicated that over-expression of VvWRKY30 conferred increased drought resistance, demonstrated by enhancements in seed germination rate and root development, as well as a decrease in water loss and stomatal aperture under drought conditions. In further study, we found that VvWRKY30 resistance to drought occurred mainly by promoting the expression of regulators of an ABA-dependent and independent signal pathway. Over-expression of VvWRKY30 also up-regulated the expressions of proline synthetase gene P5CS1, sucrose synthase gene SS4, beta-amylase gene BAM4, glucose-6-phosphate dehydrogenase gene G6PDH, and antioxidant enzyme synthesis genes Cu/ZnSOD, CAT2 and POD2. The content of proline and soluble sugar, as well as the activities of superoxide dismutase, peroxidase, and catalase were increased. Overall, our results demonstrate that VvWRKY30 positively regulates drought response by regulating ABA signal pathway, modulating proline and soluble sugar metabolism, as well as activating the scavenging systems of reactive oxygen species.

A sucrose non-fermenting-1-related protein kinase 1 gene from potato, StSnRK1, regulates carbohydrate metabolism in transgenic tobacco.

Sucrose non-fermenting-1-related protein kinase 1 (SnRK1) has been shown to play an essential role in regulating saccharide metabolism and starch biosynthesis of plant. The regulatory role of StSnRK1 from potato in regulating carbohydrate metabolism and starch accumulation has not been investigated. In this work, a cDNA encoding the SnRK1 protein, named StSnRK1, was isolated from potato. The open reading frame contained 1545 nucleotides encoding 514 amino acids. Subcellular localization analysis in onion epidermal cells indicated that StSnRK1 protein was localized to the nucleus. The coding region of StSnRK1 was cloned into a binary vector under the control of 35S promoter and then transformed into tobacco to obtain transgenic plants. Transgenic tobacco plants expressing StSnRK1 were shown to have a significant increased accumulation of starch content, as well as sucrose, glucose and fructose content. Real-time quantitative PCR analysis indicated that overexpression of StSnRK1 up-regulated the expression of sucrose synthase (NtSUS), ADP-glucose pyrophosphorylase (NtAGPase) and soluble starch synthase (NtSSS III) genes involved in starch biosynthesis in the transgenic plants. In contrast, the expression of sucrose phosphate synthase (NtSPS) gene was decreased in the transgenic plants. Meanwhile, enzymatic analyses indicated that the activities of major enzymes (SUS, AGPase and SSS) involved in the starch biosynthesis were enhanced, whereas SPS activity was decreased in the transgenic plants compared to the wild-type. These results suggest that the manipulation of StSnRK1 expression might be used for improving quality of plants in the future.

Suppression of sucrose synthase affects auxin signaling and leaf morphology in tomato.

Metabolic enzymes have been found to play roles in plant development. Sucrose synthase (SUS) is one of the two enzyme families involved in sucrose cleavage in plants. In tomato, six SUS genes have been found. We generated transgenic tomato plants with RNAi suppression of SlSUS1, SlSUS3 and SlSUS4 genes. Independent transgenic lines with RNAi suppression of more than one SUS gene exhibited morphological effects on their cotyledons and leaf structure, but there were no significant effects on their carbohydrate levels, demonstrating that SUS has a developmental function, in addition to its metabolic function. Shoot apices of the transgenic lines showed elevated expression of JAGGED (JAG) and the auxin transporter PIN1. In a PIN1-GFP fusion reporter/SUS-RNAi hybrid, PIN1-GFP patterns were altered in developing leaves (as compared to control plants), indicating that SlSUS suppression alters auxin signaling. These results suggest possible roles for SUS in the regulation of plant growth and leaf morphology, in association with the auxin-signaling pathway.

Genome-Wide Analysis of the Sucrose Synthase Gene Family in Grape (Vitis vinifera): Structure, Evolution, and Expression Profiles.

Sucrose synthase (SS) is widely considered as the key enzyme involved in the plant sugar metabolism that is critical to plant growth and development, especially quality of the fruit. The members of SS gene family have been identified and characterized in multiple plant genomes. However, detailed information about this gene family is lacking in grapevine (Vitis vinifera L.). In this study, we performed a systematic analysis of the grape (V. vinifera) genome and reported that there are five SS genes (VvSS1–5) in the grape genome. Comparison of the structures of grape SS genes showed high structural conservation of grape SS genes, resulting from the selection pressures during the evolutionary process. The segmental duplication of grape SS genes contributed to this gene family expansion. The syntenic analyses between grape and soybean (Glycine max) demonstrated that these genes located in corresponding syntenic blocks arose before the divergence of grape and soybean. Phylogenetic analysis revealed distinct evolutionary paths for the grape SS genes. VvSS1/VvSS5, VvSS2/VvSS3 and VvSS4 originated from three ancient SS genes, which were generated by duplication events before the split of monocots and eudicots. Bioinformatics analysis of publicly available microarray data, which was validated by quantitative real-time reverse transcription PCR (qRT-PCR), revealed distinct temporal and spatial expression patterns of VvSS genes in various tissues, organs and developmental stages, as well as in response to biotic and abiotic stresses. Taken together, our results will be beneficial for further investigations into the functions of SS gene in the processes of grape resistance to environmental stresses.

Grape hexokinases are involved in the expression regulation of sucrose synthase- and cell wall invertase-encoding genes by glucose and ABA.

Hexokinase (HXK, EC 2.7.1.1) is a multifunctional protein that both is involved in catalyzing the first step of glycolysis and plays an important role in sugar signaling. However, the supporting genetic evidence on hexokinases (CsHXKs) from grape (Vitis vinifera L. cv. Cabernet Sauvignon) berries has been lacking. Here, to investigate the role of CsHXK isoforms as glucose (Glc) and abscisic acid (ABA) sensors, we cloned two hexokinase isozymes, CsHXK1 and CsHXK2 with highly conserved genomic structure of nine exons and eight introns. We also found adenosine phosphate binding, substrate recognition and connection sites in their putative proteins. During grape berry development, the expression profiles of two CsHXK isoforms, sucrose synthases (SuSys) and cell wall invertase (CWINV) genes increased concomitantly with high levels of endogenous Glc and ABA. Furthermore, we showed that in wild type grape berry calli (WT), glucose repressed the expression levels of sucrose synthase (SuSy) and cell wall invertase (CWINV) genes, while ABA increased their expression levels. ABA could not only effectively improve the expression levels of SuSy and CWINV, but also block the repression induced by glucose on the expression of both genes. However, after silencing CsHXK1 or CsHXK2 in grape calli, SuSy and CWINV expression were enhanced, and the expressions of the two genes are insensitive in response to Glc treatment. Interestingly, exogenous ABA alone could not or less increase SuSy and CWINV expression in silencing CsHXK1 or CsHXK2 grape calli compared to WT. Meantime, ABA could not block the repression induced by glucose on the expression of SuSy and CWINV in CsHXK1 or CsHXK2 mutants. Therefore, Glc signal transduction depends on the regulation of CsHXK1 or CsHXK2. ABA signal was also disturbed by CsHXK1 or CsHXK2 silencing. The present results provide new insights into the regulatory role of Glc and ABA on the enzymes related to sugar metabolism in grape berry.

Expression of the Scots pine (Pinus sylvestris) TIP-like and sucrose synthase genes during two growing seasons and correlation with relative wood densities

Expression of the Scots pine (Pinus sylvestris) TIP-like and sucrose synthase genes during two growing seasons and correlation with relative wood densities

Expression of sucrose metabolism and transport genes in cassava petiole abscission zones in response to water stress

Cassava (Manihot esculenta Crantz) is an important crop, and its starch formation is regulated by sucrose metabolism and transport. To understand the roles of sucrose metabolism and transport in cassava under water stress, we studied not only sucrose metabolism and transport in cassava abscission zones (AZs) but also expression of respective genes. Sucrose was transported from leaves to roots in the early stage of water stress, and a reverse sucrose flow was detected in the later stages of the stress. The decrease in sucrose content was related to leaf senescence and inhibition of photosynthesis. Microarray analyses showed seven genes encoding sucrose synthase, nine genes encoding sucrose transporters, and eight genes encoding invertase in the cassava AZs under the water stress. Reverse transcription quantitative PCR confirmed two sucrose synthase and two invertase genes significantly upregulated under the stress, whereas one sucrose transporter gene was downregulated. The sucrose synthase and invertase gene expressions were negatively correlated with sucrose content under water stress, whereas sucrose transporter gene expressions were positively correlated with sucrose content.

Cloning, silencing, and prokaryotic expression of strawberry sucrose synthase gene FaSus1

ABSTRACTThe sucrose synthase (Sus) gene is regarded to be involved in strawberry fruit ripening; however, direct molecular and biochemical evidence is lacking. Here, the coding cDNA sequence of FaSus1 was cloned by RT-PCR and both a hairpin-mediated RNA interference pBI121 vector and a recombinant E. coli expression PET28a vector were constructed. These vectors were then used to transform strawberry fruit and for prokaryotic expression in strain BL21, respectively. The results showed that hairpin-mediated RNA silencing of FaSus1 led to a decrease in sucrose content and inhibited fruit ripening. Enzymatic activity analysis of FaSus1 showed that the reaction system contains 0.309 mg of recombinant FaSus1 protein, reaching 0.617 mg/mL. The cleavage activity of the enzyme was 0.25 U with a specific activity of 0.812 U/mg, whilst the synthetic activity of the enzyme was 0.057 U with a specific activity of 0.185 U/mg. This study provides physiological, molecular, and biochemical evidence to demonstrate that the FaSus1 has high sucrolysis activity and plays an important role in the regulation of strawberry fruit ripening.

Effects of late planting and shading on sucrose metabolism in cotton fiber

Effects of cool temperature due to late planting and low light due to shading on sucrose metabolism in cotton fiber were investigated with two cotton cultivars (Kemian 1, cool temperature-tolerant and Sumian 15, cool temperature-sensitive) at two planting dates (the optimized planting date 25 April and the late planting date 10 June) along with two shading levels of crop relative light rate (CRLR) 100% and 60% in 2010 and 2011. Compared with the optimized planting date with CRLR 100% (OPD), the acid invertase (AI) activity was little affected in the optimized planting date with CRLR 60% (OPD-CRLR 60%). The sucrose synthase (SuSy) and sucrose phosphate synthase (SPS) activities were decreased, which would reduce sucrose degradation and recycle, hindering the synthesis of cellulose. However, the sucrose concentration was decreased, which might be because of lower sucrose import from the leaf. The transcript levels of sucrose synthase gene (Susy) and sucrose phosphate synthase gene (SPS) isoforms were decreased. Comparison between the two cultivars, SPS1 was the largest down-regulated isoform in Kemian 1, but SPS2 was the largest down-regulated isoform in Sumian 15. Also, the SPS activity was more sensitive to low light for Kemian 1 than Sumian 15. Although SuSy and AI activities were much higher in the late planting date with CRLR 100% (LPD) than OPD, sucrose concentration was still high. Therefore, a lot of sucrose could not be fluently used in cellulose synthesis, leading to the decrease of cellulose concentration. The transcript levels of the three SPS isoforms increased for both cultivars. The expressions of SusyA, SusyB, and SusyC were increased for Kemian 1, but the expressions of SusyD, SusyA, SusyB, and SusyC were significantly decreased for Sumian 15. In the late planting date with CRLR 60%, no interaction effect between cool temperature and low light was observed in the concentrations of cellulose and sucrose, the activities of SPS and AI and the expression of SPS3, but was found in the transcript levels of SusyB and SPS2 for both cultivars. Also, the interaction effect was observed in the transcript levels of SusyA, SusyC, SusyD and SPS1 in Sumian 15, but was not found in Kemian 1.

EcoTILLING revealed SNPs in GhSus genes that are associated with fiber- and seed-related traits in upland cotton.

Cotton is the most important textile crop in the world due to its cellulose-enriched fibers. Sucrose synthase genes (Sus) play pivotal roles in cotton fiber and seed development. To mine and pyramid more favorable alleles for cotton molecular breeding, single nucleotide polymorphisms (SNPs) of GhSus family genes were investigated across 277 upland cotton accessions by EcoTILLING. As a result, a total of 24 SNPs in the amplified regions of eight GhSus genes were identified. These SNPs were significantly associated with at least one fiber- or seed-related trait measured in Nanjing, Anyang and Kuche in 2007–2009. Four main-effect quantitative trait nucleotides (QTNs) and five epistatic QTNs, with 0.76–3.56% of phenotypic variances explained by each QTN (PVE), were found to be associated with yield-related traits; six epistatic QTNs, with the 0.43–3.48% PVE, were found to be associated with fiber quality-related traits; and one main-effect QTN and one epistatic QTN, with the PVE of 1.96% and 2.53%, were found to be associated with seed oil content and protein content, respectively. Therefore, this study provides new information for molecular breeding in cotton.

Sucrose synthase FaSS1 plays an important role in the regulation of strawberry fruit ripening

Sugar content and composition are critical to fruit development. Sucrose, a photosynthate unloaded to the fruit, is metabolized by sucrose synthase, which might play a dominant role in sucrose accumulation during strawberry fruit ripening. However, substantial evidence regarding the molecular mechanism underlying sucrose accumulation in strawberry fruit development is lacking. Here, a strawberry sucrose synthase gene, FaSS1, was cloned and identified. Its 2421-bp cDNA includes an intact open reading frame and encodes an 806 amino acid protein, in which sucrose synthase-related conserved domains were predicted by a homology analysis. Using tobacco rattle virus-induced gene silencing, the downregulation of FaSS1 transcripts significantly delayed fruit ripening, as evidenced by the changes of firmness, and soluble sugar and anthocyanin contents, as well as the transcripts of several ripening-related genes, including PE1, PL1, XYL2, CHS, CHI, and DFR. Furthermore, the mRNA expression level of FaSS1 was inhibited by abscisic acid or sucrose, but not by glucose after fruit disc incubation in vitro. In conclusion, FaSS1 plays an important role in the regulation of strawberry fruit ripening, and its expression could be inhibited by abscisic acid and sucrose.

Transcriptome analysis reveals the accumulation mechanism of anthocyanins in ‘Zijuan’ tea (Camellia sinensis var. asssamica (Masters) kitamura) leaves

Anthocyanin biosynthesis in herbaceous plants has been studied widely, but the mechanism of anthocyanin accumulation in ‘Zijuan’ tea remains unclear. In this study, the leaf transcriptome of ‘Zijuan’ tea was analyzed at the purple and green stages by using the Illumina HiSeq 2500 platform. A total of 2250 unigenes were differentially expressed at the purple and green stages. Anthocyanin biosynthesis and carbohydrate metabolism were enriched through the KEGG metabolic pathway analysis of the differentially expressed unigenes. The upregulated sucrose synthase gene in the purple leaves may provide hexoses and UDP-glucose for anthocyanin synthesis. The genes encoding the corresponding enzymes in the glycolysis pathway were upregulated, whereas the expression of those genes encoding the enzymes in the TCA cycle showed no obvious change. Increased acetyl-CoA may contribute to anthocyanin accumulation through the upregulated cytosolic acetyl-coenzyme A carboxylase (ACCase) gene in the purple leaves of ‘Zijuan’ tea, indicating that glycolysis may provide more intermediates as substrates for promoting anthocyanin accumulation. The physiological and qRT-PCR results were consistent with the RNA-Seq data. Our findings expand our knowledge on the metabolic regulation of anthocyanin synthesis in tea plants.

Dynamic Changes in Starch Metabolism and Endogenous Hormones during Stolon Formation in Tulipa edulis

The stolon is the main asexual reproductive organ of the medicinal plant Tulipa edulis and has special morphology. In the greenhouse experiment presented herein, the dynamic changes in carbohydrates and related enzymes, proteins, and endogenous hormones of stolons during T. edulis stolon formation were investigated. The results showed that the content of total soluble sugar, sucrose, reducing sugar, fructose, and starch were all significantly enhanced in the middle period when stolon emerged and maintained at relatively high levels until the later period of stolon formation, while protein content decreased during stolon formation. The activities of amylase (AMY), sucrose phosphate synthase (SPS), and sucrose synthase (SS) peaked in the initial period and were negatively correlated with soluble sugars. However, adenosine diphosphoglucose pyrophosphorylase (AGPase) activity increased as stolon formation progressed, and the changes in soluble starch synthase (SSS), granule-bound starch synthase (GBSS) activities presented a single peak, reaching their maximums in the middle period. AGPase, SSS, and GBSS activities were all positively related to starch content. Moreover, quantitative real-time polymerase chain reaction (qRT-PCR) verified the changes in SS and SSS activities via the expression levels of the SS, SSSI, and SSSII genes. The gibberellin (GA) and zeatin riboside (ZR) content attained their maximum in the initial period of stolon formation. Indole-3-acetic acid (IAA) and abscisic acid (ABA) remained at high levels during the initial and middle period and decreased significantly during the later period of stolon formation, inversely to the ratio of ABA:IAA. Analysis of the physiological changes in T. edulis stolon indicated that the accumulation of soluble sugars and starch via various enzymes, a high level of IAA and a low ABA to IAA ratio mainly contributed to stolon development of T. edulis. This paper explored carbohydrate levels and endogenous hormones profiles during stolon formation, which provided the theory basis for further regulating stolon growth of T. edulis.

Dynamic Metabolic Regulation by a Chromosome Segment from a Wild Relative During Fruit Development in a Tomato Introgression Line, IL8-3.

We performed comparative metabolome and transcriptome analyses throughout fruit development using the tomato cultivar M82 and its near-isogenic line IL8-3, with interesting and useful traits such as a high content of soluble solids. Marked differences between M82 and IL8-3 were found not only in ripe fruits but also at 20 days after flowering (DAF) in the hierarchical clustering analysis of the metabolome, whereas patterns were similar between the two genotypes at 10 and 30 DAF. Our metabolome analysis conclusively showed that 20 DAF is an important stage of fruit metabolism and that the Solanum pennellii introgressed region in IL8-3 plays a key role in metabolic changes at this stage. Carbohydrate and amino acid metabolism were found to be promoted in IL8-3 at 20 DAF and the ripening stage, respectively, whereas transcriptome analysis showed no marked differences between the two genotypes, indicating that dynamic metabolic regulation at 20 DAF and the ripening stage was controlled by relatively few genes. The transcript levels of the cell wall invertase (LIN6) and sucrose synthase (TOMSSF) genes in starch and sucrose metabolic pathway and that of the glutamate synthase (SlGOGAT) gene in the amino acid metabolic pathway in IL8-3 fruit were higher than those in M82, and SlGOGAT expression was enhanced under high-sugar conditions. The results suggest that the promotion of carbohydrate metabolism by LIN6 and TOMSSF in IL8-3 fruit at 20 DAF affects SlGOGAT expression and amino acid accumulation via higher sugar concentration at the late stage of fruit development.

Suboptimal Light Conditions Influence Source-Sink Metabolism during Flowering.

Reliance on carbohydrates during flower forcing was investigated in one early and one late flowering cultivar of azalea (Rhododendron simsii hybrids). Carbohydrate accumulation, invertase activity, and expression of a purported sucrose synthase gene (RsSUS) was monitored during flower forcing under suboptimal (natural) and optimal (supplemental light) light conditions, after a cold treatment (7°C + dark) to break flower bud dormancy. Post-production sucrose metabolism and flowering quality was also assessed. Glucose and fructose concentrations and invertase activity increased in petals during flowering, while sucrose decreased. In suboptimal light conditions RsSUS expression in leaves increased as compared to optimal light conditions, indicating that plants in suboptimal light conditions have a strong demand for carbohydrates. However, carbohydrates in leaves were markedly lower in suboptimal light conditions compared to optimal light conditions. This resulted in poor flowering of plants in suboptimal light conditions. Post-production flowering relied on the stored leaf carbon, which could be accumulated under optimal light conditions in the greenhouse. These results show that flower opening in azalea relies on carbohydrates imported from leaves and is source-limiting under suboptimal light conditions.

Establishing gene models from the Pinus pinaster genome using gene capture and BAC sequencing.

BackgroundIn the era of DNA throughput sequencing, assembling and understanding gymnosperm mega-genomes remains a challenge. Although drafts of three conifer genomes have recently been published, this number is too low to understand the full complexity of conifer genomes. Using techniques focused on specific genes, gene models can be established that can aid in the assembly of gene-rich regions, and this information can be used to compare genomes and understand functional evolution.ResultsIn this study, gene capture technology combined with BAC isolation and sequencing was used as an experimental approach to establish de novo gene structures without a reference genome. Probes were designed for 866 maritime pine transcripts to sequence genes captured from genomic DNA. The gene models were constructed using GeneAssembler, a new bioinformatic pipeline, which reconstructed over 82 % of the gene structures, and a high proportion (85 %) of the captured gene models contained sequences from the promoter regulatory region. In a parallel experiment, the P. pinaster BAC library was screened to isolate clones containing genes whose cDNA sequence were already available. BAC clones containing the asparagine synthetase, sucrose synthase and xyloglucan endotransglycosylase gene sequences were isolated and used in this study. The gene models derived from the gene capture approach were compared with the genomic sequences derived from the BAC clones. This combined approach is a particularly efficient way to capture the genomic structures of gene families with a small number of members.ConclusionsThe experimental approach used in this study is a valuable combined technique to study genomic gene structures in species for which a reference genome is unavailable. It can be used to establish exon/intron boundaries in unknown gene structures, to reconstruct incomplete genes and to obtain promoter sequences that can be used for transcriptional studies. A bioinformatics algorithm (GeneAssembler) is also provided as a Ruby gem for this class of analyses.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2490-z) contains supplementary material, which is available to authorized users.