Gerbera Research Articles

Transcriptome profiling of Gerbera hybrida reveals that stem bending is caused by water stress and regulation of abscisic acid

BackgroundGerbera hybrida is one of the most popular cut flowers in the world; however, stem bending, which always happens when gerbera flower harvested from the field, greatly limits its vase life. To date the molecular mechanisms underlying stem bending remain poorly understood.ResultsIn this study, we performed high-throughput transcriptome sequencing of gerbera during stem bending using the Illumina sequencing technology. Three cDNA libraries constructed from mRNAs of gerbera stem at stem bending stage 0, 2 and 4 were sequenced. More than 300 million high-quality reads were generated and assembled into 96,492 unigenes. Among them, 34,166 unigenes were functionally annotated based on similarity search with known protein. Sequences derived from plants at different stem bending stages were mapped to the assembled transcriptome, and 9,406 differentially expressed genes (DEGs) were identified. Through Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, specific pathways were identified during the stem bending process, such as phenylpropanoid biosynthesis pathway, phenylalanine metabolism pathway, starch and sucrose metabolism pathway, and plant hormone signal transduction pathway. A total of 211 transcription factors (TFs), including TF families involved in plant senescence, such as NAC, MYB, WRKY, and AP2/ERF members, as well as TFs related to water stress tolerance, were shown to be regulated during stem bending. Gene Onotology (GO) functional enrichment analysis indicated that key genes involved in responses to osmotic and oxidative stresses were also varied in expression during this process. Furthermore, analysis of DEGs involved in the hormone signaling pathways and determination of endogenous abscisic acid (ABA) content showed that stem bending may be an ethylene-independent process, but regulated by ABA. In short, our findings suggested that the stem bending of cut gerbera may be caused by the involvement of water stress and regulation of ABA during the postharvest life.ConclusionsThe transcriptome sequences provide a valuable resource in revealing the molecular mechanism underlying stem bending of cut flower and offer novel genes that can be used to guide future studies for ornamental plant breeding.

The Effect of Temperature on Plant Growth in Four Gerbera hybrida Cultivars

Temperature is one of the main factors that affects the growth pattern of Gerbera hybrida, which shows vast variation in morphology and stress adaptation among cultivars. However, little is known about temperature responses of plant growth among different cultivars. In this study, four cultivars were planted in different growth temperatures to investigate the effect of temperature on plant growth of Gerbera hybrida during their vegetative growth. Results showed that the optimum growth temperature of the four cultivars was 20 °C, of which plant height, root length, biomass accumulation, leaf area, and photosynthetic rate were enhanced significantly. Different cultivars showed diverse temperature adaptation ranges, which were related with their genetic background, and the temperature adaptability of cultivar Autumn was the best among the four cultivars. Temperature also had significant effects on photosynthetic rate, which was the main factor shaping plant growth. Our research provides the basic guidance for the growth temperature control in the cultivation of Gerbera hybrida.

Genetic Analysis and Vase Life Characteristics of a New Bright-Pink Gerbera Cultivar ‘Pink Garden’ with Double Flowers

Genetic Analysis and Vase Life Characteristics of a New Bright-Pink Gerbera Cultivar ‘Pink Garden’ with Double Flowers

The roles of sodium nitroprusside, salicylic acid, and methyl jasmonate as hold solutions on vase life of Gerbera jamesonii ‘Sun Spot’

TThe present study investigates the roles of nitroprusside (SNP), salicylic acid (SA), methyl jasmonate (MJ), and their interaction with 8-hydroxyquinoline sulfate (8-HQS) in regulating the peroxidase activity (POX), water uptake, the relative water content (RWC), the contents of malondialdehyde (MDA), soluble sugar, proline, and protein content in the petals and the stem bending of Gerbera jamesonii ‘Sun Spot’ cut flowers. Cut flowers were treated with various concentrations (50, 100, and 200 µM) of hold-solutions containing 8-HQS, SA, MJ, and SNP. Hold solutions were used alone or in combination with 100 µM 8-HQS for 24 h. Distilled water was used as control and sucrose (4%, w/v) was added to all solutions. The findings showed that 50 µM SA+ 100 µM 8-HQS markedly improved the RWC, the contents of proline, anthocyanin, carotenoid, protein, and soluble sugar, and activities of POX in the petals and markedly reduced water loss and the contents of MDA in the petals, compared with other treatments, especially the control. Meanwhile, the combination of plant growth regulators (PGR) with 8-HQS markedly improved positive indexes than use alone PGR. This phenomenon seemed to be due to more absorption of PGR. Among different concentrations of PGR, 50 μM is the most effective treatment for the improvement of the vase life of Gerbera jamesonii cut flowers. The results also demonstrated that SA+8-HQS improves the vase life of gerbera cut flowers by enhancing the membrane stability and water retaining capacity as well as increasing proline, antioxidant activity, and pigment contents.

Effects of pre-harvest applications of different source of calcium on the cell wall fractions and stem bending disorder of Gerbera (Gerbera jamesonii L.) cultivar flowers

Gerbera flower belongs to the composite family and is one of the top five cut flowers in the world in terms of production and consumption, which has a great economic value in the international flowering industry. This study was designed to evaluate whether calcium pre-harvest application, provided through 0, 0.5, 1 and 1.5% of calcium chloride (CaCl2) and calcium nitrate (CaNO3), could extend the day of stem bending of gerbera cut flower. In the present study, we used two gerbera cultivars ‘Intense’ and ‘Rosaline’ as resistant and sensitive to stem bending, respectively. For evaluation of associated traits with stem bending, the produced flowers were kept in a vase solution containing 200 mg/L hydroxyquinoline with temperature conditions of 20°C. The results showed that day of stem bending of flowers extended 9.62 and 10.37 days by application of 1% CaCl2 for ‘Rosaline’ and ‘Intense’ respectively. All treatments were effective in the increasing relative water content of flower due to increase water uptake. The results also revealed that the calcium pretreatment delayed flowers senescence and increased antioxidant enzyme activity. Application of calcium resulted in an increase in membrane stability index in the cut flowers of both cultivars, providing evidence for delay of senescence in calcium-treated cut flowers. Also, results showed that calcium application significantly increased lignin, cellulose and hemicellulose content of both cultivars. The maximum and the minimum lignin and cellulose content were observed in resistant and sensitive cultivars, respectively. In general, pre-harvest application of calcium (especially 1% CaCl2) with increasing of antioxidant enzyme activity and stem lignification led to decreasing of stem bending disorder in both cultivars.

Engineering de novo anthocyanin production in Saccharomyces cerevisiae

BackgroundAnthocyanins are polyphenolic pigments which provide pink to blue colours in fruits and flowers. There is an increasing demand for anthocyanins, as food colorants and as health-promoting substances. Plant production of anthocyanins is often seasonal and cannot always meet demand due to low productivity and the complexity of the plant extracts. Therefore, a system of on-demand supply is useful. While a number of other (simpler) plant polyphenols have been successfully produced in the yeast Saccharomyces cerevisiae, production of anthocyanins has not yet been reported.ResultsSaccharomyces cerevisiae was engineered to produce pelargonidin 3-O-glucoside starting from glucose. Specific anthocyanin biosynthetic genes from Arabidopsis thaliana and Gerbera hybrida were introduced in a S. cerevisiae strain producing naringenin, the flavonoid precursor of anthocyanins. Upon culturing, pelargonidin and its 3-O-glucoside were detected inside the yeast cells, albeit at low concentrations. A number of related intermediates and side-products were much more abundant and were secreted into the culture medium. To optimize titers of pelargonidin 3-O-glucoside further, biosynthetic genes were stably integrated into the yeast genome, and formation of a major side-product, phloretic acid, was prevented by engineering the yeast chassis. Further engineering, by removing two glucosidases which are known to degrade pelargonidin 3-O-glucoside, did not result in higher yields of glycosylated pelargonidin. In aerated, pH controlled batch reactors, intracellular pelargonidin accumulation reached 0.01 µmol/gCDW, while kaempferol and dihydrokaempferol were effectively exported to reach extracellular concentration of 20 µM [5 mg/L] and 150 µM [44 mg/L], respectively.ConclusionThe results reported in this study demonstrate the proof-of-concept that S. cerevisiae is capable of de novo production of the anthocyanin pelargonidin 3-O-glucoside. Furthermore, while current conversion efficiencies are low, a number of clear bottlenecks have already been identified which, when overcome, have huge potential to enhance anthocyanin production efficiency. These results bode very well for the development of fermentation-based production systems for specific and individual anthocyanin molecules. Such systems have both great scientific value for identifying and characterising anthocyanin decorating enzymes as well as significant commercial potential for the production of, on-demand, pure bioactive compounds to be used in the food, health and even pharma industries.

Bioengineering triacetic acid lactone production in Yarrowia lipolytica for pogostone synthesis.

Yarrowia lipolytica is an oleaginous yeast that is recognized for its ability to accumulate high levels of lipids, which can serve as precursors to biobased fuels and chemicals. Polyketides, such as triacetic acid lactone (TAL), can also serve as a precursor for diverse commodity chemicals. This study used Y. lipolytica as a host organism for the production of TAL via expression of the 2-pyrone synthase gene from Gerbera hybrida. Induction of lipid biosynthesis by nitrogen-limited growth conditions increased TAL titers. We also manipulated basal levels of TAL production using a DNA cut-and-paste transposon to mobilize and integrate multiple copies of the 2-pyrone synthase gene. Strain modifications and batch fermentation in nitrogen-limited medium yielded TAL titers of 2.6 g/L. Furthermore, we show that minimal medium allows TAL to be readily concentrated at >94% purity and converted at 96% yield to pogostone, a valuable antibiotic. Modifications of this reaction scheme yielded diverse related compounds. Thus, oleaginous organisms have the potential to be flexible microbial biofactories capable of economical synthesis of platform chemicals and the generation of industrially relevant molecules.

Effects of Growing Season, Plant Stage of Development, and Substrate Drench Applications of Paclobutrazol as Compared to a Daminozide Standard on Growth and Flowering of Gerbera Daisy ‘Bright Red with Light Eye'1

AbstractPaclobutrazol substrate drenches at 0, 1, 2, 3, or 4 ppm were compared to a 2,500 ppm daminozide foliar spray standard in two finishing seasons (fall 2015 and spring 2016) and at two application stages for plant size control and improved market quality of ‘Bright Red with Light Eye' Gerbera daisy (Gerbera jamesonii Hook. f. ‘Bright Red with Light Eye') in 12.7cm (5 in) pots. Stage 1 was when the majority of plants had roots to the bottom of the substrate, and stage 2 was 2 weeks later. A consumer preference survey assessed purchasing preference when plants had two or three open flowers. Plant size index, foliage height, peduncle length, flower diameter, and quality rating at first flower decreased linearly while days to first flower increased quadratically with increasing paclobutrazol concentration, regardless of stage or season. Paclobutrazol applications delayed flowering, and decreased flower diameter and flower and bud counts, but these differences were small and not considered of practical importance. Based on quality rating at first flower and survey results, a 1 or 2 ppm paclobutrazol drench produced the most marketable plants in fall, and 0, 1, 2, or 3 ppm produced the most marketable plants in spring.Index words: plant growth retardant, B-Nine, Bonzi, greenhouse productionChemicals used in this study: B-Nine (daminozide) [butanedioic acid mono (2,2- dimethylhydrazide)] and Bonzi (paclobutrazol) [(±)-(R*,R*)-β-[(4-Chlorophenyl)methyl]-α-(1,1- dimethylethyl)-lH-1,2,4-triazole-1-ethanol]Species used in this study: ‘Bright Red with Light Eye' Gerbera daisy (Gerbera jamesonii Hook. f. ‘Bright Red with Light Eye')

Influence of dehydration techniques on colour retention and related traits of gerbera (Gerbera hybrida) flowers

Gerbera (Gerbera hybrida) is the most popular florist flower due to various colours, shapes and sizes. It belongs to the family Asteraceae. The present study was conducted to determine the effect of different drying techniques on retention of flower colour and its related traits of Gerbera hybrida var. Doni. Maximum flower colour acceptability score (3.67), high acceptability of texture of dry flowers (3.67), minimum brittleness of dried flowers (2.33), minimum damage of florets (1.33) and maximum score (2.67) for the shape of embedded dry flowers were observed with vacuum air oven drying upto 60 days. Maximum colour retention up to 60 days was observed on the adaxial surface of the floret in vacuum drying (Y-O14A); however, on the abaxial surface of the floret, colour retention was seen maximum up to 60 days at room temperature drying, i.e. control (Y-12B) technique. Minimum reduction in flower size (5.22 %) was observed in vacuum drying; however, minimum reduction in flower weight (82.21%) was foundin microwave drying technique. Vacuum air oven drying method was observed to be the best technique for retention of flower colour and related traits.

GhWIP2, a WIP zinc finger protein, suppresses cell expansion in Gerbera hybrida by mediating crosstalk between gibberellin, abscisic acid, and auxin.

Cell expansion is a key determinant for the final size and shape of plant organ, and is regulated by various phytohormones. Zinc finger proteins (ZFPs) consist of a superfamily involved in multiple aspects of organ morphogenesis. However, little is known about WIP-type ZFP function in phytohormone-mediated organ growth. Using reverse genetics, RNA-seq and phytohormone quantification, we elucidated the role of a new WIP-type ZFP from Gerbera hybrida, GhWIP2, in controlling organ growth via regulation of cell expansion. GhWIP2 localizes to the nucleus and acts as a transcriptional repressor. Constitutive overexpression of GhWIP2 (GhWIP2OE) in both Gerbera and Arabidopsis thaliana caused major developmental defects associated with cell expansion, including dwarfism, short petals, scapes, and petioles. Furthermore, GhWIP2OE plants were hypersensitive to GA, but not to ABA, and showed a reduction in endogenous GA and auxin, but not ABA concentrations. Consistent with these observations, RNA-seq analysis revealed that genes involved in GA and auxin signaling were down-regulated, while those involved in ABA signaling were up-regulated in GhWIP2OE plants. Our findings suggest that GhWIP2 acts as a transcriptional repressor, suppressing cell expansion during organ growth by modulating crosstalk between GA, ABA, and auxin.

A coupled in vitro/in vivo approach for engineering a heterologous type III PKS to enhance polyketide biosynthesis in Saccharomyces cerevisiae.

Polyketides are attractive compounds for uses ranging from biorenewable chemical precursors to high-value therapeutics. In many cases, synthesis in a heterologous host is required to produce these compounds in industrially relevant quantities. The type III polyketide synthase 2-pyrone synthase (2-PS) from Gerbera hybrida was used for the production of triacetic acid lactone (TAL) in Saccharomyces cerevisiae. Initial in vitro characterization of 2-PS led to the identification of active site variants with improved kinetic properties relative to wildtype. Further in vivo evaluation in S. cerevisiae suggested certain 2-PS mutations altered enzyme stability during fermentation. In vivo experiments also revealed beneficial cysteine to serine mutations that were not initially explored due to their distance from the active site of 2-PS, leading to the design of additional 2-PS enzymes. While these variants showed varying catalytic efficiencies in vitro, they exhibited up to 2.5-fold increases in TAL production when expressed in S. cerevisiae. Coupling of the 2-PS variant [C35S,C372S] to an engineered S. cerevisiae strain led to over 10 g/L TAL at 38% of theoretical yield following fed-batch fermentation, the highest reported to date. Our studies demonstrate the success of a coupled in vitro/in vivo approach to engineering enzymes and provide insight on cysteine-rich enzymes and design principles toward their use in non-native microbial hosts.

Comparative transcriptome analysis of two Gerbera hybrida cultivars revealed cold tolerance mechanism

Comparative transcriptome analysis of two Gerbera hybrida cultivars revealed cold tolerance mechanism

Effects of nano-silver pulsing, calcium sulfate and gibberellin on an antioxidant molecule and vase life of cut gerbera flowers

Abstract: The aim of this study was to evaluate interactions between NS coupled with CS and GA on flavonoid, cell membrane behavior and extending the vase life of cut gerbera. Pulse treatments of flowers in NS at concentrations 0 (DI), 3 or 9 mg/l for 24 h. Then, flowers were treated with preservative solutions containing calcium sulfate (0, 10 or 20 mM) and GA 4+7 (0 or 20 mg/l), plus 1.5% sucrose in all preservative solutions. Pulse treatments with 3 or 9 mg NS/l and holding in solution containing 20 mM CS compared to the control treatment (holding in the solution of sucrose following pulse treatment in DI) significantly extended vase life by 8 days. According to the antioxidant role of flavonoids, and lower amounts of flavonoid in the flowers that pre-treated with NS, therefore, it may be said that NS prevented from microbial attack.

Transcriptional control of anthocyanin biosynthesis genes and transcription factors associated with flower coloration patterns in Gerbera hybrida.

We analyzed the expression of anthocyanin biosynthesis genes and transcription factors (TFs) in the Gerbera hybrida cultivars 'Bintang' and 'Alliance' that exhibit different coloration patterns. Differential expression of biosynthesis genes and TFs was associated with variable anthocyanin content at different flower developmental stages (S1-S3) in both cultivars; higher anthocyanin content was correlated with higher levels of gene expression. Exposure to different temperatures (6 and 22°C) also resulted in different anthocyanin content levels: the lower temperature (6°C) enhanced anthocyanin content compared to the higher temperature (22°C). However, the increased anthocyanin content of 'Bintang' compared to 'Alliance' was the result of higher levels of expression of all detected genes, regardless of flower stage and temperature conditions. Therefore, we conclude that transcriptional control of the detected genes is associated with the mechanisms of anthocyanin biosynthesis and coloration patterns in gerberas; however, further studies of the key genes are needed.

Calcium improves gerbera (Gerbera hybrida) vase life

The vase life of Gerbera hybrida cut flowers is about two weeks. To prevent wilting, hypochlorite is widely used in vase water to control micro-organisms that may block xylem cells and restrict water uptake. In this study, three levels of calcium chloride (0, 12 and and 24 meq L−1), two levels of calcium hypochlorite (0 and 25 mg L−1) and two levels of hydrochloric acid (0 and 2 meq L−1) were factorially arranged, using three replicates in a completely randomised design. A single gerbera flower with a 450 mm stem in a glass bottle with 500 mL treated water was used as experimental unit. The trial was ended after 17 d in a room at 25 °C. The general appearance index of the stemmed flowers was significantly (p < 0.0001) correlated (r 0.81) with its mass-retention percentage. Calcium hypochlorite significantly improved water uptake as well as the mass-retention percentage. The highest CaCl2 level of 24 meq L−1 significantly improved the mass-retention percentage without significantly improved water uptake, an indication that cell walls of the xylem tubes could have been hardened, producing stronger flower stems. Indications of a positive effect with application of hydrochloric acid (HCl), only in the presence of optimum levels of hypochlorite and calcium, needs further investigation.

A Mini Zinc-Finger Protein (MIF) from Gerbera hybrida Activates the GASA Protein Family Gene, GEG, to Inhibit Ray Petal Elongation.

Petal appearance is an important horticultural trail that is generally used to evaluate the ornamental value of plants. However, knowledge of the molecular regulation of petal growth is mostly derived from analyses of Arabidopsis thaliana, and relatively little is known about this process in ornamental plants. Previously, GEG (Gerbera hybrida homolog of the gibberellin [GA]–stimulated transcript 1 [GAST1] from tomato), a gene from the GA stimulated Arabidopsis (GASA) family, was reported to be an inhibitor of ray petal growth in the ornamental species, G. hybrida. To explore the molecular regulatory mechanism of GEG in petal growth inhibition, a mini zinc-finger protein (MIF) was identified using yeast one-hybrid (Y1H) screen. The direct binding of GhMIF to the GEG promoter was verified by using an electrophoretic mobility shift assay and a dual-luciferase assay. A yeast two-hybrid (Y2H) revealed that GhMIF acts as a transcriptional activator. Transient transformation assay indicated that GhMIF is involved in inhibiting ray petal elongation by activating the expression of GEG. Spatiotemporal expression analyses and hormone treatment assay showed that the expression of GhMIF and GEG is coordinated during petal development. Taken together, these results suggest that GhMIF acts as a direct transcriptional activator of GEG, a gene from the GASA protein family to regulate the petal elongation.

Dissecting functions of SEPALLATA-like MADS box genes in patterning of the pseudanthial inflorescence of Gerbera hybrida.

The pseudanthial inflorescences of the sunflower family, Asteraceae, mimic a solitary flower but are composed of multiple flowers. Our studies in Gerbera hybrida indicate functional diversification for SEPALLATA (SEP)-like MADS box genes that often function redundantly in other core eudicots. We conducted phylogenetic and expression analysis for eight SEP-like GERBERA REGULATOR OF CAPITULUM DEVELOPMENT (GRCD) genes, including previously unstudied gene family members. Transgenic gerbera plants were used to infer gene functions. Adding to the previously identified stamen and carpel functions for GRCD1 and GRCD2, two partially redundant genes, GRCD4 and GRCD5, were found to be indispensable for petal development. Stepwise conversion of floral organs into leaves in the most severe RNA interference lines suggest redundant and additive GRCD activities in organ identity regulation. We show conserved and redundant functions for several GRCD genes in regulation of flower meristem maintenance, while functional diversification for three SEP1/2/4 clade genes in regulation of inflorescence meristem patterning was observed. GRCD genes show both specialized and pleiotropic functions contributing to organ differentiation and flower meristem fate, and uniquely, to patterning of the inflorescence meristem. Altogether, we provide an example of how plant reproductive evolution has used conserved genetic modules for regulating the elaborate inflorescence architecture in Asteraceae.

Transcriptome analysis reveals the regulation of brassinosteroids on petal growth in Gerbera hybrida.

Gerbera hybrida is a cut-flower crop of global importance, and an understanding of the mechanisms underlying petal development is vital for the continued commercial development of this plant species. Brassinosteroids (BRs), a class of phytohormones, are known to play a major role in cell expansion, but their effect on petal growth in G. hybrida is largely unexplored. In this study, we found that the brassinolide (BL), the most active BR, promotes petal growth by lengthening cells in the middle and basal regions of petals, and that this effect on petal growth was greater than that of gibberellin (GA). The RNA-seq (high-throughput cDNA sequencing) technique was employed to investigate the regulatory mechanisms by which BRs control petal growth. A global transcriptome analysis of the response to BRs in petals was conducted and target genes regulated by BR were identified. These differentially expressed genes (DEGs) include various transcription factors (TFs) that were activated during the early stage (0.5 h) of BL treatment, as well as cell wall proteins whose expression was regulated at a late stage (10 h). BR-responsive DEGs are involved in multiple plant hormone signal pathways, hormone biosynthesis and biotic and abiotic stress responses, showing that the regulation of petal growth by BRs is a complex network of processes. Thus, our study provides new insights at the transcriptional level into the molecular mechanisms of BR regulation of petal growth in G. hybrida.

Erratum to: Genetic mapping and QTL analysis of Botrytis resistance in Gerbera hybrida

Erratum to: Genetic mapping and QTL analysis of Botrytis resistance in Gerbera hybrida

Genetic mapping and QTL analysis of Botrytis resistance in Gerbera hybrida

Gerbera hybrida is an economically important cut flower. In the production and transportation of gerbera with unavoidable periods of high relative humidity, grey mould occurs and results in losses in quality and quantity of flowers. Considering the limitations of chemical use in greenhouses and the impossibility to use these chemicals in auction or after sale, breeding for resistant gerbera cultivars is considered as the best practical approach. In this study, we developed two segregating F1 populations (called S and F). Four parental linkage maps were constructed using common and parental specific SNP markers developed from expressed sequence tag sequencing. Parental genetic maps, containing 30, 29, 27 and 28 linkage groups and a consensus map covering 24 of the 25 expected chromosomes, could be constructed. After evaluation of Botrytis disease severity using three different tests, whole inflorescence, bottom (of disc florets) and ray floret, quantitative trait locus (QTL) mapping was performed using the four individual parental maps. A total of 20 QTLs (including one identical QTL for whole inflorescence and bottom tests) were identified in the parental maps of the two populations. The number of QTLs found and the explained variance of most QTLs detected reflect the complex mechanism of Botrytis disease response.