Exogenous Application Of Gibberellic Acid Research Articles

The bHLH transcription factor SlPRE2 regulates tomato fruit development and modulates plant response to gibberellin.

SlPRE2 is gibberellin inducible and mediates plant response to gibberellin. Silencing of SlPRE2 decreases tomato fruit size, pericarp thickness, placenta size and seed size by regulating cell expansion. Gibberellin is one of the crucial hormones essential for plant growth and developmental processes, including seed germination, stem elongation, and sex expression. Previous studies indicated gibberellin could control fruit development by regulation of genes downstream gibberellin pathway. In the present study, we found that the SlPRE2, a bHLH family transcription factor gene, is highly expressed in immature green fruit. Silencing of SlPRE2 caused reduction of fruits size, pericarp thickness, and placenta size. Meanwhile, smaller seeds were observed in SlPRE2 silenced lines. In addition, the SlPRE2-silenced fruit mesocarp had reduced cell size and expression of SlXTH2 and SlXTH5 which are involved in cell enlargement. Further research showed that SlPRE2 is gibberellic acid-inducible and the expression of gibberellin metabolism-related genes in immature green fruit was affected by the downregulation of SlPRE2. Moreover, the SlPRE2-silenced plants had changed responses to application of exogenous gibberellic acid and paclobutrazol, an inhibitor of gibberellin biosynthesis. These findings indicated that SlPRE2 is a regulator of fruit development and affects plant response to gibberellic acid via the gibberellin pathway.

Exogenous application of gibberellic acid and ascorbic acid improved tolerance of okra seedlings to NaCl stress

Accumulation of salts in soils has become a serious environmental threat for plant growth and causes considerable loss in yield. Okra Abelmoschus esculentus L. is an important crop and sensitive to saline stress. In the present study, to explore methods for growing okra in salty area, exogenous gibberellic acid (GA3) and ascorbic acid (AsA) were foliage applied on okra seedling under NaCl stress. The results showed that treatment with 100 mM NaCl decreased shoot length, root length, fresh weight, dry weight, contents of chlorophyll pigments and nutrient elements, enhanced levels of electrolyte leakage, H2O2, lipid peroxidation and activities of antioxidant enzymes. Treatments with 0.1 mM GA3 and/or 0.1 mM AsA could alleviated harmful effects of saline stress on okra seedlings by improving growth indicators, increasing contents of chlorophyll and carotenoids, stimulating activities of antioxidant enzymes and decreasing electrolyte leakage, H2O2 content and lipid peroxidation. Moreover, concentrations of K, Ca, Mg and Fe in leaves and roots as well as levels of osmo-protectants (proline and soluble protein) increased in response to treatment with GA3 + AsA in NaCl-stressed okra seedling. Overall, foliar application of GA3 and/or AsA demonstrated benefits to okra seedlings in salty environments. Combined application of GA3 and AsA was more effective than sole use of GA3 or AsA alone.

Arabidopsis defense mutant ndr1-1 displays accelerated development and early flowering mediated by the hormone gibberellic acid

NONRACE-SPECIFIC DISEASE RESISTANCE (NDR1) is a widely characterized gene that plays a key role in defense against multiple bacterial, fungal, oomycete and nematode plant pathogens. NDR1 is required for activation of resistance by multiple NB and LRR-containing (NLR) protein immune sensors and contributes to basal defense. The role of NDR1 in positively regulating salicylic acid (SA)-mediated plant defense responses is well documented. However, ndr1-1 plants flower earlier and show accelerated development in comparison to wild type (WT) Arabidopsis plants, indicating that NDR1 is a negative regulator of flowering and growth. Exogenous application of gibberellic acid (GA) further accelerates the early flowering phenotype in ndr1-1 plants, while the GA biosynthesis inhibitor paclobutrazol attenuated the early flowering phenotype of ndr1-1, but not to WT levels, suggesting partial resistance to paclobutrazol and enhanced GA response in ndr1-1 plants. Mass spectroscopy analyses confirmed that ndr1-1 plants have 30–40% higher levels of GA3 and GA4, while expression of various GA metabolic genes and major flowering regulatory genes is also altered in the ndr1-1 mutant. Taken together this study provides evidence of crosstalk between the ndr1-1-mediated defense and GA-regulated developmental programs in plants.

Exogenous application of gibberellic acid participates in up-regulation of lipid biosynthesis under salt stress in rice

Alterations in membrane lipid composition lead to improved plant salt tolerance. Gibberellic acid (GA3) has also been widely reported to reduce growth inhibition induced by increased salinity. However, little is known about whether exogenous application of GA3 participates in up-regulation of lipid biosynthesis under salt stress. In this study, one of the major lipid biosynthesis genes in rice (Oryza sativa L. cv. Nipponbare), monogalactosyldiacylglycerol synthase (OsMGD) was found to be significantly up-regulated by GA3 treatment. Lipid analysis showed that after salt disturbance, the concentrations of all the measured lipids, including monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and phospholipid lipids + sulfoquinovosyl diacylglycerol (PL + SQDG) were decreased significantly. However, GA3 treatment prior to salt disturbance caused those lipids to remain at high levels, as well as preserving a high DGDG/MGDG ratio. The desaturation of DGDG (DBI) was also increased in GA3 pre-treatment plants as compared with no GA3 pre-treatment, primarily due to a decrease of 16:0 fatty acids and an increase of 18:3 fatty acids in DGDG. Plants pre-treated with GA3 prior to salt disturbance had higher dry weights than those without pre-treatment. The chlorophyll concentration was also higher in GA3 treated plants than in untreated plants under salt disturbance. Taken together, these results indicate that exogenous application of GA3 participates in up-regulation of chloroplast lipid biosynthesis under salt disturbance in rice.

Embryo rescue of Spondias tuberosa and exogenous application of gibberellic acid

The umbuzeiro (Spondias tuberosa Arruda) is a native fruit tree of Caatinga and has great economic importance. Its fruits are collected extractivistically due to lack of commercial plantations. Furthermore, the seeds have physical dormancy, which reduces germination rates. However, tissue culture can be used to overcome such problems by excision and in vitro culture of embryos with gibberellin. The objective of this study was to evaluate different disinfection times of zygotic embryos in sodium hypochlorite (NaOCl) and the effect of gibberellic acid (GA(3)) in the in vitro establishment of excised embryos. For aseptic test, zygotic embryos (15 replicates/treatment) were excised and immersed in NaOCl (1.25% active chlorine) for different times (5, 10, and 15 min) and rinsed three times with distilled and sterilized water. The explants were cultured on Murashige and Skoog medium (MS) supplemented with 2.88 µM GA(3). After 30 days we evaluated the contamination and germination percentages. The influence of different concentrations of GA(3) was also tested. Zygotic embryos (24 replicates/treatment) were inoculated onto MS medium with different concentrations of GA(3) (0.0, 0.72, 1.44, and 2.88 µM). After 30 days the germination and normal seedlings percentage, height, number of leaves, fresh and dry weight of shoot and root were evaluated. The experimental design of both trials was completely randomized. The immersion in NaOCl for more than 10 min reduced contamination as well as the germination percentage (p=0.0281). The effect of GA(3) was significant (p=0.0346) in stem elongation in a concentration of 2.88 µM compared to control without gibberellin. The 10-min time was effective in disinfection and gibberellic acid promotes increased height of seedlings.

Crescimento de plantas e vigor de sementes de feijão em resposta à aplicação exógena de ácido giberélico

The objective of this work was to evaluate the growth and vigor expression of bean seeds from plants submitted to the application of gibberellic acid. The treatments consisted of the application of gibberellic acid in concentrations of zero; 50; 100 and 200 mg.L-1 in the V2 stage. The samples for growth analysis were performed at regular intervals of seven days after sowing, until the plants reached the R9 stage. At each collection, the plants were separated into organs for determination of growth and dry matter partition. In addition, the harvest index, mass of one thousand seeds, number of seeds per plant, insertion of the first pod, length and total dry matter of seedlings were determined. Total dry matter, dry matter production rates and solar energy conversion efficiency are higher in plants submitted to the exogenous application of gibberellic acid. The harvest index as well as the number of seeds per plant present a tendency of reduction with the increase of the gibberellic acid concentration. However, the mass of one thousand seeds tends to be higher in the dose of 50 mg.L-1. The vigor of bean seeds, evaluated by the test of seedling length, is altered with application of gibberellic acid.

Improvement Yield and Quality of Dahlia Flowers by Exogenous Application of Gibberellic Acid and Salicylic Acid under Sandy soil Conditions

Dahlia is one of the popular cut flowers in the world which characterized by the rich variety and attractive flower colors. Hence, in a field study 100, 200, 300mgL−1 gibberellic acid (GA3) and salicylic acid (SA) were used during two successive seasons 2015 and 2016 to determine the possible role of each growth regulator in improving marketable quality, increasing yield and vase life of dahlia. Results indicated that the tallest plants (118.43cm) were those sprayed with GA3 at 200mgL-1. Additionally, it showed that foliar application of GA3 or SA at 200mgL−1 significantly increased the number of branches plant-1, fresh and dry weight plant-1, leaf numbers, leaf area plant-1, flower numbers, flower quality and vase life as well as tuber length, and numbers plant-1. The most rapid flowering (39.57 days after planting) occurred when plants were sprayed with GA3 at 200mgL1. Concomitant to the enhancement in the vegetable and flowering attributes, an increscent in the anthocyanin content and total soluble solids was observed in the petals by increasing GA3 and SA concentrations up to 200mgL−1. Additionally, a significant increment in the total chlorophyll content was recorded with GA3 and SA treatments. In conclusion, the vegetative and flowering characters of dahlia could be improved by application of either GA3 or SA.

Gibberellin Inhibits Floral Initiation in the Perennial Woody Plant Jatropha curcas

Gibberellin (GA) is an important phytohormone and has been reported to promote flowering in annual and biennial plants, but may play an opposite role in woody perennial plants. In this study, the promoting or inhibiting effect of GA on floral initiation was investigated in Jatropha curcas L., a perennial woody plant, which has great potential as renewable energy plant due to the high oil content in the seed. We found that exogenous application of gibberellic acid (GA3) inhibited flowering, whereas GA biosynthesis inhibitors promoted flowering. The promotive effect of the GA biosynthesis inhibitor paclobutrazol on floral initiation could be diminished by GA3 treatment. The expression levels of GA biosynthesis genes Jatropha GA 3-oxidase 3 (JcGA3ox3) and the GA receptor genes, Jatropha GA-INSENSITIVE DWARF 1C (JcGID1C) were decreased, whereas a GA catabolism gene, Jatropha GA 2-oxidase 8 (JcGA2ox8), was elevated during floral transition. These results suggest that GA inhibits floral initiation in J. curcas.

Exogenous Application of Gibberellic Acid Improves Flowering in Kalanchoë

Kalanchoë is an economically important genus comprising numerous potted plants and recently is also emerging as cut flowers. However, the lack of information about flower-inducing factors limits the number of species that can be used in commercial production and breeding programs. Therefore, the aim of this study was to investigate the effects of exogenous application of gibberellic acid (GA3) on flower induction and flowering quality of Kalanchoë longiflora and Kalanchoë pinnata. The experiment was conducted under a short day (SD) photoperiod with a day temperature of 22 °C and a night temperature of 15 °C for 8 weeks. The treatments consisted of four applications of either 0.25 or 0.50 μg of GA3 per plant per week, providing a total of 100 μg or 200 μg/plant and 0 μg/plant for the control. The volume of 100 μL of GA3 solution containing 1% agarose was applied to the shoot apex using a pipette. For both species, flowering was enhanced by the GA3 treatments compared with the control plants. Gibberellin-treated plants flowered earlier, produced more inflorescences, and exhibited an increased number of flowers compared with the control plants. Moreover, the GA3 treatments in K. longiflora delayed the appearance of wilted flowers. Plant height increased in plants that received GA3, but the number of nodes did not differ from the control plants. Thus, we conclude that the application of GA3 improves flowering of Kalanchoë species and can be a useful tool for the production of cut flower cultivars.

Exogenous gibberellic acid application induces the overexpression of key genes for pedicel lignification and an increase in berry drop in table grape

Most table grape (Vitis vinifera L.) varieties require gibberellic acid (GA3) applications to obtain an adequate berry size in order to satisfy market requirements. However, GA3 treatments also produce severe berry drop in some cultivars, which occurs mainly after a cold storage period during post-harvest. Berry drop in bunches treated with GA3 has been related to the hardening and thickening of the pedicel produced by the over-accumulation of cellulose and its lignification. The main goal of this study was to compare the morphology and gene expression in pedicel samples of genotypes contrasting for berry drop susceptibility. These genotypes are Thompson Seedless, which exhibits a low incidence of berry drop, and a genetic line (Line #23) of INIA's breeding program that is very susceptible to berry drop at harvest and after storage in bunches sprayed with GA3. The parameters measured to study this phenomenon during fruit growth and post-harvest storage included fruit detachment force (FDF), hardness and thickness of the pedicel and berry drop frequency. Histological analyses of pedicel structures at harvest showed an increase in cell size and deposition of lignin in the cortex zone in both contrasting genotypes treated with GA3. The expression profile in both genotypes of the key lignin biosynthesis genes Vv4CL4, VvCCR1L and VvCAD1 analyzed by quantitative real time PCR (qPCR) revealed evident changes in response to GA3 treatments. In particular, gene VvCAD1 is overexpressed (100X) in pedicels of line #23 treated with GA3 after 30 and 45 days in cold storage compared to control. Moreover, the frequency of berry drop was higher for Line #23 treated with GA3 than for the control (23% vs. 1%). Our results suggest that gibberellic acid regulates the expression of the biosynthesis of lignin genes, generating changes in cell wall composition and pedicel structure that result in an increase in berry drop.

Effect of decapitation and exogenous application of gibberellic acid (GA3) and cytokinin (CK) on some physiological characteristics of stevia.

Stevia (Stevia rebaudiana B.) has auxiliary buds that often remain dormant for a long time and sometimes remain dormant until the plants change at the reproductive stage. This study was designed out to investigate whether decapitation and exogenous application of plant growth regulators enhance the productivity of stevia through breaking the apical dominance and increasing physiological characteristics. Experiment was carried out as a factorial in randomized complete block design with three replications. Factors were consisted two agricultural practices (Decapitation and No-decapitation) and eight foliar spray including without spray as control, water spray, GA3 (300, 600 and 900 µm) and CK (100, 200 and 400 µm). The results of the present investigation indicated a positive response on number of branches and leaves, leaves and stem fresh weight and total dry weight, in both harvests not only from the decapitation of apical buds but also from foliar application of CK (400 µM). Thus, it can be concluded that the decapitation practices in conjunction with foliar application of CK (400 µM) could be used to increase the dry-leaf yield of stevia. However, further studies are required to standardize the dose of CK (400 µM) to improve the yield and quality of stevia.

Cold-Induced Male Meiotic Restitution in Arabidopsis thaliana Is Not Mediated by GA-DELLA Signaling.

Short periods of cold stress induce male meiotic restitution and diploid pollen formation in Arabidopsis thaliana by specifically interfering with male meiotic cytokinesis. Similar alterations in male meiotic cell division and gametophytic ploidy stability occur when gibberellic acid (GA) signaling is perturbed in developing anthers. In this study, we found that exogenous application of GA primarily induces second division restitution (SDR)-type pollen in Arabidopsis, similar to what cold does. Driven by the close similarity in cellular defects, we tested the hypothesis that cold-induced meiotic restitution is mediated by GA-DELLA signaling. Using a combination of chemical, genetic and cytological approaches, however, we found that both exogenously and endogenously altered GA signaling do not affect the cold sensitivity of male meiotic cytokinesis. Moreover, in vivo localization study using a GFP-tagged version of RGA protein revealed that cold does not affect the expression pattern and abundance of DELLA in Arabidopsis anthers at tetrad stage. Expression study found that transcript of RGA appears enhanced in cold-stressed young flower buds. Since our previous work demonstrated that loss of function of DELLA causes irregular male meiotic cytokinesis, we here conclude that cold-induced meiotic restitution is not mediated by DELLA-dependent GA signaling.

Gender-specific expression of GIBBERELLIC ACID INSENSITIVE is critical for unisexual organ initiation in dioecious Spinacia oleracea.

While unisexual flowers have evolved repeatedly throughout angiosperm families, the actual identification of sex-determining genes has been elusive, and their regulation within populations remains largely undefined. Here, we tested the mechanism of the feminization pathway in cultivated spinach (Spinacia oleracea), and investigated how this pathway may regulate alternative sexual development. We tested the effect of gibberellic acid (GA) on sex determination through exogenous applications of GA and inhibitors of GA synthesis and proteasome activity. GA concentrations in multiple tissues were estimated by enzyme-linked immunosorbent assay analysis. Gene function was investigated and pathway analysis was performed through virus-induced gene silencing. Relative gene expression levels were estimated by quantitative reverse transcription-polymerase chain reaction. Inhibition of GA production and proteasome activity feminized male flowers. However, there was no difference in GA content in tissues between males and females. We characterized a single DELLA family transcription factor gene (GIBBERELLIC ACID INSENSITIVE (SpGAI)) and observed inflorescence expression in females two-fold higher than in males. Reduction of SpGAI expression in females to male levels phenocopied exogenous GA application with respect to flower development. These results implicate SpGAI as the feminizing factor in spinach, and suggest that the feminizing pathway is epistatic to the masculinizing pathway. We present a unified model for alternative sexual development and discuss the implications for established theory.

Exogenous Application of Gibberellic Acid Improves the Maize Crop Productivity Under Scarce and Sufficient Soil Moisture Condition

AbstractDrought stress creates imbalance or deficiency of some growth regulators in plants, which leads toward reduced crop yield. Gibberellic acid is one of the most important growth regulators in plants, which improve drought tolerance in plants under optimum concentration. A field experiment was conducted under exogenous application of gibberellic acid under normal or drought condition and with or without gibberellic acid application. Crop growth and yield parameters were assesses during the experimentation. Study revealed that crop reduced growth in term of leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), net assimilation rate (NAR) and total dry matter (TDM) under drought condition, while these parameters were improved with gibberellic acid application. Similary, improved growth rate resulted in better performance of yield attributes (cob length, cob diameter, grains per cob, grain weight and yield). Gibberellic acid application improved the crop performance at optimum irrigation, as well as under reduced irrigation. Although highest crop yield was recorded with gibberellic acid application under optimum irrigation level, while its application under drought stress improved crop tolerance and resulted in better crop yield, similar to optimum irrigation level. Exogenous application of gibberellic acid not only improved the drought tolerance in maize, but also increased the crop yield under normal condition.

Forward Genetics by Sequencing EMS Variation-Induced Inbred Lines

In order to leverage novel sequencing techniques for cloning genes in eukaryotic organisms with complex genomes, the false positive rate of variant discovery must be controlled for by experimental design and informatics. We sequenced five lines from three pedigrees of ethyl methanesulfonate (EMS)-mutagenized Sorghum bicolor, including a pedigree segregating a recessive dwarf mutant. Comparing the sequences of the lines, we were able to identify and eliminate error-prone positions. One genomic region contained EMS mutant alleles in dwarfs that were homozygous reference sequences in wild-type siblings and heterozygous in segregating families. This region contained a single nonsynonymous change that cosegregated with dwarfism in a validation population and caused a premature stop codon in the Sorghum ortholog encoding the gibberellic acid (GA) biosynthetic enzyme ent-kaurene oxidase. Application of exogenous GA rescued the mutant phenotype. Our method for mapping did not require outcrossing and introduced no segregation variance. This enables work when line crossing is complicated by life history, permitting gene discovery outside of genetic models. This inverts the historical approach of first using recombination to define a locus and then sequencing genes. Our formally identical approach first sequences all the genes and then seeks cosegregation with the trait. Mutagenized lines lacking obvious phenotypic alterations are available for an extension of this approach: mapping with a known marker set in a line that is phenotypically identical to starting material for EMS mutant generation.

Comparative Transcriptome Analysis between Gynoecious and Monoecious Plants Identifies Regulatory Networks Controlling Sex Determination in Jatropha curcas.

Most germplasms of the biofuel plant Jatropha curcas are monoecious. A gynoecious genotype of J. curcas was found, whose male flowers are aborted at early stage of inflorescence development. To investigate the regulatory mechanism of transition from monoecious to gynoecious plants, a comparative transcriptome analysis between gynoecious and monoecious inflorescences were performed. A total of 3,749 genes differentially expressed in two developmental stages of inflorescences were identified. Among them, 32 genes were involved in floral development, and 70 in phytohormone biosynthesis and signaling pathways. Six genes homologous to KNOTTED1-LIKE HOMEOBOX GENE 6 (KNAT6), MYC2, SHI-RELATED SEQUENCE 5 (SRS5), SHORT VEGETATIVE PHASE (SVP), TERMINAL FLOWER 1 (TFL1), and TASSELSEED2 (TS2), which control floral development, were considered as candidate regulators that may be involved in sex differentiation in J. curcas. Abscisic acid, auxin, gibberellin, and jasmonate biosynthesis were lower, whereas cytokinin biosynthesis was higher in gynoecious than that in monoecious inflorescences. Moreover, the exogenous application of gibberellic acid (GA3) promoted perianth development in male flowers and partly prevented pistil development in female flowers to generate neutral flowers in gynoecious inflorescences. The arrest of stamen primordium at early development stage probably causes the abortion of male flowers to generate gynoecious individuals. These results suggest that some floral development genes and phytohormone signaling pathways orchestrate the process of sex determination in J. curcas. Our study provides a basic framework for the regulation networks of sex determination in J. curcas and will be helpful for elucidating the evolution of the plant reproductive system.

Relative expression of genes of menthol biosynthesis pathway in peppermint (Mentha piperita L.) after chitosan, gibberellic acid and methyl jasmonate treatments

Menthol as an important component of monoterpenes essential oil in peppermint (Mentha piperita L.) is widely applied for medical and industrial uses. In this study, the effect of exogenous applications of chitosan (200 mg/L), gibberellic acid (50 mg/L) and methyl jasmonate (300 μM) was investigated in the main genes of menthol biosynthesis pathways within a 72 h time period using qRT-PCR. Transcript levels of most genes were either unaffected or down-regulated following chitosan treatment relative to control plants. Decreasing of geranyl diphosphate synthase (GDS) and limonene synthase (LS) genes transcript in chitosan treatment could possibly be effective in reducing of limonene level. On the other hand, it seems that an increase in menthone-menthol reductase (MMR) transcription level at 72 h under these treatments had a positive role in increasing the amount of menthol in this plant. Since exogenous application of gibberellic acid (GA3) down-regulated transcript levels of several genes involved in menthol biosynthesis, there is this expectance that GA3 treatment might not have a prominent role in enhancing menthol yield via transcription regulation. Transcript level of the majority genes after methyl jasmonate treatment gradually increased and reached the highest level at 72 h, therefore, it is possible that methyl jasmonate improves medicinal properties of M. piperita.

Osmotic stress- and salt stress-inhibition and gibberellin-mitigation of leaf elongation associated with up-regulation of genes controlling cell expansion

Leaf elongation rates (LER) is sensitive to salt stress and osmotic stress, and gibberellic acid (GA) may mediate stress-inhibition of leaf elongation by affecting genes controlling cell expansion. The objectives of this study were to examine the differential inhibitory effects of osmotic stress and salt stress on LER for fast- and slow-growing genotypes of tall fescue (Festuca arundinacea) and to determine whether GA could mitigate stress-induced decline in LER. Plants of fast-growing ‘K-31′ and slow-growing ‘Bonsai’ were grown hydroponically and treated with GA under either osmotic or salt stress. LER of both genotypes were inhibited by osmotic and salt stress (46–86%) due to reduced cell elongation and production rate. ‘Bonsai’ LER was reduced to a greater extent than that of ‘K-31′ due to greater reduction in cell production rate. Exogenous GA application significantly enhanced LER regardless of stress for both genotypes, which was more pronounced in ‘Bonsai’ than in ‘K-31′ caused by greater cell elongation and production rates. Quantitative PCR analysis revealed that four expansin genes (EXPA4, EXPA5, EXPA7 and EXPB7) and one XET gene (XET2) were down-regulated by osmotic stress and EXPA7 was down-regulated by salt stress in both genotypes. Three expansin genes (EXPA4, EXPA5 and EXPA7) were up-regulated by GA treatment in both genotypes under non-stress conditions, in which EXPA4 was also up-regulated by GA treatment in both genotypes under osmotic stress. The expression level of XET1 and XET3 increased in ‘K-31′ and ‘Bonsai’, respectively, with exogenous GA treatment under non-stress and salt stress. This study demonstrated the roles of GA regulation of genetic variations in leaf differential responses to osmotic and salt stress involving different expansins and XET genes.

Influence of plant growth regulators on Expansin2 expression in strawberry fruit. Cloning and functional analysis of FaEXP2 promoter region

FaEXP2 encodes a fruit-specific expansin that is known to be associated with cell wall loosening and fruit softening in strawberry (Fragaria×ananassa Duch.). In spite of its relevant role in fruit ripening, little is known about the hormonal regulation of this gene. In the present study, we isolated a 650bp fragment of the FaEXP2 gene promoter and the in silico analysis revealed the presence of cis-acting elements associated with hormones, light and stress-related responses. With the aim of characterizing the hormonal regulation of FaEXP2 expression, strawberry fruit were treated with plant growth regulators and changes in transcript levels were analyzed by qPCR. FaEXP2 expression levels were significantly higher than control in fruit treated with abscisic acid (ABA), and when the endogenous source of auxins (achenes) was removed. In contrast, transcript accumulation was not affected by exogenous applications of gibberellic acid (GA3), naphtalenacetic acid (NAA), ethylene or 1-methylcyclopropene (1-MCP). Also, functional analysis of FaEXP2 gene promoter was performed by transient and permanent strawberry transformation. Histochemical GUS staining analysis showed that the 650bp-promoter fragment was able to drive the reporter gene expression specifically to the receptacle and along ripening. Our results provide new insights into the hormonal regulation of FaEXP2 expression.

Overexpression of Rice OsGAI in Rice and Tobacco Modulates Gibberellic Acid‐Dependent Responses

ABSTRACTGibberellin, or gibberellic acid (GA), is a crucial phytohormone for its role in overall plant growth and development, particularly in the regulation of plant height. Among the GA‐signaling mutants, the gai (GA insensitive) gene has been well studied in Arabidopsis [Arabidopsis thaliana (L.) Heynh.] system. The wild‐type GAI, being a DELLA‐family protein, acts as a nuclear‐localized GA‐signaling repressor that restrains the expression of other genes associated with GA‐induced growth processes. Here we document alteration in GA‐dependent multiple responses obtained through overexpression and expression of the rice (Oryza sativa L.) wild‐type GAI (OsGAI) gene in the endogenous (rice) and heterologous (tobacco [Nicotiana tabacum L.]) plant systems, respectively. In both cases, the transgenic lines were found to have significantly reduced plant height, decreased seed α‐amylase activity, reduced early seedling growth, a higher level of anthocyanin pigmentation, and reduced stem cell‐wall lignifications. Leaf chlorophyll content was found to be increased in transgenic rice but decreased in transgenic tobacco lines. The reduced lignification in transgenic tobacco was observed to be reversible on exogenous GA application and correlated to the hypersensitivity toward oxidative stress. Findings of the present research advance our understanding on the complex interplay between GAI and interacting molecules responsible for several physiological processes in plant systems.