Histological,transcriptomic,and gene functional analyses reveal the regulatory events underlying gibberellin-induced parthenocarpy in tomato

Gibberellin(GA)is one of the major plant hormones that promote parthenocarpy,a highly valuable agronomic trait.Here,we demonstrated that exogenous GA3application triggered the formation of parthenocarpic fruits with smaller size but unchanged shape in tomato(Solanum lycopersicum).These fruits exhibited a thicker pericarp,undeveloped ovules,and few jelly tissues,leading to smaller locules with empty cavities.Histological investigation showed that GA treatment produced more cell layers with larger cells in the pericarp,suggesting its promotion in both cell division and expansion.Transcriptomic analyses between GA-3and mock-treated unpollinated ovaries/fruits identified a large number of differentially expressed genes related to hormones,cell division,cell expansion,and transcription factors,implying that they coordinately regulated parthenocarpy conferred by GA.In particular,the downregulation of five reported repressors of tomato parthenocarpy,including two auxin signaling components,AUXIN RESPONSE FACTOR5(SlARF5)and Sl ARF7,and three MADS-box genes,TOMATO APETALA3(TAP3),TOMATO PISTILLATA(TPI),and AGAMOUS-LIKE6(SlAGL6),after GA treatment might play a key role in this process.Furthermore,we found that the knockdown of a GA signaling factor SlMYB33,which was depressed by GA treatment,induced parthenocarpic fruit set in tomato,an effect that might have been achieved by enhancing GA biosynthesis and decreasing the expression of some repressors of tomato parthenocarpy.Thus,our results provide a basis for understanding the regulatory mechanism of GA in tomato parthenocarpy.

EjGASA6 promotes flowering and root elongation by enhancing gibberellin biosynthesis

The Gibberellic Acid-stimulated Arabidopsis(GASA)gene family is involved in the regulation of gene expression and plant growth,development,and stress responses.To investigate the function of loquat GASA genes in the growth and developmental regulation of plants,a loquat EjGASA6 gene homologous to Arabidopsis AtGASA6 was cloned.EjGASA6 expression was induced by gibberellin,and ectopic transgenic plants containing this gene exhibited earlier bloom and longer primary roots since these phenotypic characteristics are related to higher gibberellin content.Transcriptome analysis and qRT-PCR results showed that the expression levels of GA3ox1 and GA20ox1,which encode key enzymes in gibberellin biosynthesis,were significantly increased.Furthermore,we confirmed that EjGASA6 could promote the expression of GA20ox1 via the luciferase reporter system.Overall,our results suggest that EjGASA6 promotes blooming and main-root elongation by positively regulating gibberellin biosynthesis.These findings broaden our understanding of the role of GASAs in plant development and growth,and lay the groundwork for future research into the functions of EjGASA6 in regulating loquat growth and development.

BEAR1, a bHLH transcription factor, controls seedling growth by regulating gibberellins biosynthesis in rice

The genetic pathways of rice seedling growth have a major impact on seedling emergence from soil and development.In this study,we identified a new bHLH transcription factor,BEAR1,from rice RNAi mutant library.Both the BEAR1-RNAi and bear1 CRISPR mutants had accelerated seedling growth.Histological section of leaves showed accelerated development of lacuna and vascular bundles in bear1 mutant.GUS staining revealed that BEAR1 was highly expressed in coleoptiles and leaves at seedling stage.Expression analysis of gibberellin(GA)biosynthesis and metabolic genes and content determination of active GAs indicated that the expression of GA biosynthesis genes,especially OsKS4 and OsCPS2,were upregulated and the GAs content were significantly increased in bear1,which correlated with the seedling phenotype of bear1 mutant.Molecular and biochemical assays revealed that BEAR1 directly binds to the promoter of OsKS4,thereby repressing its expression.Haplotypes analysis showed clear differentiation in indica and japonica rice varieties,and a strong correlation with seedling height.These findings provide novel insights into the regulation of seedling growth in rice.

Effect of Exogenous Gibberellin on Wheat Seed Germination under Salt Stress

[Objectives]In this experiment,wheat seeds were treated with different concentrations of gibberellin and different concentrations of salt solution to study the change of germination index of wheat seeds.[Methods]The germination rate,germination potential and germination index of wheat seeds were measured by routine methods,and the effect of exogenous gibberellin on germination of wheat seeds under salt stress was observed.[Results]The germination rate,germination potential and germination index of wheat seeds under salt stress were significantly increased after exogenous treatment of 0.25 and 0.50 g/L gibberellin within the range of salt concentration gradient.However,when the concentration of gibberellin was too high,it would inhibit the germination of seeds.[Conclusions]Appropriate concentration of gibberellin can effectively alleviate the stress caused by salt on wheat seed germination.In this experiment,the best concentration of gibberellin to alleviate salt stress was 0.25 g/L.

Exogenous Application of Abscisic Acid or Gibberellin Acid Has Different Effects on Starch Granule Size Distribution in Grains of Wheat

Granule size distribution of wheat starch is an important characteristic that can affect its chemical composition and the functionality of wheat products. Two high-yield winter wheat cultivars were used to evaluate the effects of the application of exogenous ABA or GA during the reproductive phase of the initial grain filling on starch granule size distribution and starch components in grains at maturity. The results indicated that a bimodal curve was found in the volume and surface area distribution of grain starch granules, and a unimodal curve was observed for the number distribution under all treatments. The exogenous ABA resulted in a significant increase in the proportions （both by volume and by surface area） of B-type （〈9.9 Ixm in diameter） starch granules, with a reduction in those of A-type （〉9.9 ~tm） starch granules, while, the exogenous GA3 led to converse effects on size distribution of those starch granules. The exogenous ABA also increased starch, amylose and amylopectin contents at maturity but significantly reduced the ratio of amylose to amylopectin. Application of GA3 significantly reduced starch content, amylopectin content but increased the ratio of amylose to amylopectin. The ratio of amylose to amylopectin showed a significant and negative relationship with the volume proportion of granules 〈9.9 μm, but was positively related to the volume proportion of granules 22.8-42.8 μm.

Crosstalk of cold and gibberellin effects on bolting and flowering in flowering Chinese cabbage

The flower stalk is the product organ of flowering Chinese cabbage(Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee),which is cultivated extensively in South China.Flower stalk formation and development,including bolting and flowering,determine the yield of flowering Chinese cabbage;however,the bolting and flowering mechanisms remain to be explored.To elucidate these processes,we studied the effects of low-temperature and gibberellin(GA)treatments,and their interaction,on stem elongation,bolting time,flowering time,hormone content,and cell morphology in stem of flowering Chinese cabbage.The results showed that both cold and GA treatments accelerated bolting time,stem elongation,and flowering time.Moreover,cold and GA cotreated plants displayed additive positive effects.In addition,cold treatments increased the GA,indole-3-acetic acid,and cytokinin contents and altered cell size in the shoot apices of flowering Chinese cabbage.Treatment with uniconazole,a GA synthesis inhibitor,strongly delayed bolting time,stem elongation,and flowering time,whereas GA,but not cold treatment,rescued this inhibition,indicating that low temperature accelerates bolting and flowering not only through inducing GA in the shoot apices,but also other ways.These results provide a theoretical basis for further dissecting the regulatory mechanism of bolting and flowering in flowering Chinese cabbage.

Gibberellins,brassinolide,and ethylene signaling were involved in flower differentiation and development in Nelumbo nucifera

Hormones play important roles in vegetative and reproductive processes;however,the regulatory roles of hormones in Nelumbo nucifera(Lotus)growth and development are unclear.In this study,nine types of endogenous hormones,including gibberellins(GA_1,GA_3,and GA_4),indole-3-acetic acid(IAA),brassinolide(BR),ethylene(ETH),jasmonic acid(JA),abscisic acid(ABA),and zeatin(ZT)were detected in dormant shoot tips,vegetative shoot tips,developing leaf buds,and developing flower buds of lotus.The results indicated that GA,ETH,and BR signaling can promote vegetative and reproductive development of lotus.GA signaling regulates plant height and stimulates flower bud differentiation.GA levels were the highest in the flower buds;exogenous GA3+4 increased plant height by approximately 90%,increased flower quantity by nearly 40%,and advanced flowering by 4 d.Suppressing GA biosynthesis using paclobutrazol decreased plant height and flower quantity by 38%and 87.1%,respectively,and delayed flowering by 15.6 d.ETH signaling has positive regulatory effects on vegetative growth and flower development.The ETH concentration in the developing leaf buds was at least 50%higher than that in other samples.Ethephon spraying led to remarkable increases in plant height and leaf thickness and extended the flowering duration.BR signaling acts as a growth promoter during vegetative and reproductive development in lotus.The highest BR levels were detected in the vegetative shoot tips.External application of28-epihomobrassinolide resulted in growth-promoting phenotypes including longer scapes,thicker leaves,and prolonged flowering.

Seed Germination Traits of Loquat (Eriobotrya japonica Lindl.) as Affected by Various Pre-Sowing Treatments (Cutting of Cotyledons, Removal of Perisperm, Moist Chilling and/or Exogenous Application of Gibberellin)

The purpose of this study was to investigate the effects of various presowing treatments on the germinability(final germination percentage)and germination rate of loquat seeds in order to increase seedling production in nurseries(applied research)as well as provide answers for important physiological issues related to loquat seeds and their seed coat(basic research).Three experiments were carried out with various pre-sowing treatments.These treatments included full or partial removal of seed coat(perisperm),partial cutting of cotyledons as well as moist chilling at 5℃ for 13 days and/or soaking the seeds in water or 250 ppm gibberellic acid(GA_(3))solution for 24 h.According to the results,cotyledons excision resulted in delayed germination,regardless of the presence or absence of the seed coat in comparison with the decoated seeds that demonstrated the highest germination rate amongst them.In addition,even the partial excision of seed coats affected positively both the germinability and the germination rate,compared to the control-intact seeds.Furthermore,control-intact seeds had a higher germination percentage when exposed to moist chilling independently of the application or not of gibberellin;while the combination of gibberellin application and moist chilling improved both the percentage and the rate of germination of decoated seeds.In conclusion,the role of perisperm(seed coat)in the germination procedure of loquat seeds seems to be important,indicating the existence of seed coat-imposed dormancy on loquat seeds.Finally,the existence of a mild endogenous embryo-dormancy on loquat is also discussed.

Oligo-carrageenan kappa increases C, N and S assimilation, auxin and gibberellin contents, and growth in Pinus radiata trees

Oligo-carrageenans （OCs） obtained from pure carrageenans extracted from marine red algae stimulate growth by enhancing photosynthesis and basal metabolism in tobacco plants and Eucalyptus trees. In addition, OCs stimulate secondary metabolism, increasing the level of metabolites involved in defense against pathogens. In this work, we analyzed the effect of OC kappa on the increase in height, in activities of basal metabolism enzymes in- volved in carbon, nitrogen and sulphur assimilation, ribu- lose 1,5 biphosphate carboxylase/oxygenase （rubisco）, glutamate dehydrogenase （GDH） and O-acetylserine thiol- lyase （OASTL）, and in the level of growth-promoting hormones, the auxin indole acetic acid （IAA） and the gibberellin GA3, in pine （Pinus radiata） trees treated with OC kappa at concentrations of 1 and 5 mg mL-1 and cultivated for 9 months without additional treatment. Pines treated with OC kappa at 1 mg mL-1 showed a similar increase in height but displayed a higher increased in total chlorophyll, activities of rubisco, GDH and OASTL and level of IAA and GA3 than those treated with OC kappa at 5 mg mL-1. Thus, OC kappa stimulates growth and basal metabolism and increases the level of growth-promoting hormones in pine trees, mainly at 1 mg mL-1.

Stereoselective Functionalization at C-2 and C-3 of the Gibberellin via an Intramolecular Free Radical Cyclization Approach

Stereoselective functionalization at C-2 and C-3 of the gibberellin skeleton was achieved via an intramolecular free radical cyclization approach using a tethered C-19 halomethyl ester as the radical precursor.

Comparison of Effect of Brassinosteroid and Gibberellin Biosynthesis Inhibitors on Growth of Rice Seedlings

Brassinosteroid（BR） and gibberellin（GA） are two predominant plant hormones that regulate plant cell elongation. Mutants disrupt the biosynthesis of these hormones and display different degrees of dwarf phenotypes in rice. Although the role of each plant hormone in promoting the longitudinal growth of plants has been extensively studied using genetic methods, their relationship is still poorly understood. In this study, we used two specific inhibitors targeting BR and GA biosynthesis to investigate the roles of BR and GA in growth of rice seedlings. Yucaizol, a specific inhibitor of BR biosynthesis, and Trinexapac-ethyl, a commercially available inhibitor of GA biosynthesis, were used. The effect of Yucaizol on rice seedlings indicated that Yucaizol significantly retarded stem elongation. The IC_（50） value was found to be approximately 0.8 μmol/L. Yucaizol also induced small leaf angle phenocopy in rice seedlings, similarly to BR-deficient rice, while Trinexapac-ethyl did not. When Yucaizol combined with Trinexapac-ethyl was applied to the rice plants, the mixture of these two inhibitors retarded stem elongation of rice at lower doses. Our results suggest that the use of a BR biosynthesis inhibitor combined with a GA biosynthesis inhibitor may be useful in the development of new technologies for controlling rice plant height.

Brassinosteroid and gibberellin coordinate rice seed germination and embryo growth by regulating glutelin mobilization

Seed germination is the beginning of a new lifecycle,and involves many complex physiological and biochemical reactions including seed reserve mobilization in the endosperm and nutrient transport and reuse in the embryo.Although glutelin is a dominant storage protein in rice,its contribution to seed germination and its regulatory mechanisms are mostly unknown.Gibberellin (GA) and brassinosteroid (BR),two major growth-promoting phytohormones,also play positive roles in controlling seed germination.However,how GA and BR interact and coordinate seed germination and facilitate glutelin mobilization remains unclear.In the present study,biochemical and physiological analyses of seed germination indicated that both GA and BR promote seed germination and post-germination growth.Exogenous application of GA restored germination defects caused by BR deficiency or insensitivity.Proteomic and q RT-PCR results showed that the expression of several glutelin proteins and their encoding genes was induced by BR and GA in the embryo.Expression assays suggested that the increased accumulation of glutelin protein in the embryo was due to the accelerated degradation of glutelin by a cysteine proteinase (REP-1) in the endosperm.The breakdown of glutelin in the endosperm showed a strict positive correspondence with the length of the shoot.The GluA2 mutation led to reduced degradation rate of glutelin and defects in seed germination,and the promotion effect of GA on seed germination was weakened in the glua2mutant.In vitro culture assay of rice embryos showed that glutelin mobilization functioned downstream of the GA and BR pathways to promote shoot elongation.These findings suggest a mechanism that mediates crosstalk between BR and GA in co-regulating rice seed germination and embryo growth.

The heading-date gene Ghd7 inhibits seed germination by modulating the balance between abscisic acid and gibberellins

Seed dormancy of cultivated rice was largely weakened during the progress of domestication.Correct timing and uniformity of seed germination are important for rapid seedling establishment and highyield production.In the present study,we found that the heading-date gene Ghd7 acted as a negative regulator of germination.A mutant of ghd7 showed low sensitivity to exogenous ABA treatment during seed germination.Further investigation revealed reduced accumulation of ABA in mature ghd7 seeds as a consequence of dampened expression of OsNCED genes.Moreover,elevated GA_(3) level was detected in seeds of ghd7 mutant during imbibition course,which was attributed to the induction of genes responsible for the synthesis pathways of bioactive GAs.Thus,Ghd7 inhibits seed germination by increasing the ABA/GA_(3) ratio.Besides revealing pleiotropic effects of Ghd7,our results indicate its role in linking seed germination to growth-phase transition in rice,which would enrich the theoretical basis for future breeding practices.

Stable Isotope Dilution Analysis of Gibberellin Residues in Tomato Paste by Liquid Chromatography-Tandem Mass Spectrometry

An accurate and sensitive method for the simultaneous determination of gibberellic acid（GA3）, gibberellin A4（GA4） and gibberellin A7（GA7） residues in tomato paste was developed by coupling solid phase extraction to high performance liquid chromatography-tandem mass spectrometry（LC-MS/MS） with electrospray ionization based stable isotope dilution analysis（SIDA）. The isotope labeled internal standard can compensate for the losses during the extraction and cleanup steps and for discrimination due to ion suppression. After extraction from methanol, hydrophile lipophilic balance（HLB） solid phase extraction（SPE） column was tested for the capacity of the cleanup of the tomato paste in compared with C18 SPE column which is the common way to the detection of GAs, and the former gained better result. Spiked experiments were performed in the non-contaminated tomato pastes and the recoveries of GA3, GA4 and GA7 were 42.6%―75.0% in external standard method（ESM） and 91.1%―103.8% in internal standard method（ISM） respectively. The validities of this method were investigated and good analytical performance for the three GAs was obtained, including low limits of method detection（2 ng/g for GA3 and GA4, 0.3 ng/g for GA7）, excellent linear dynamic ranges（5―500 ng/g for GA3 and GA4, 1―100 ng/g for GA7） and good relative standard deviation ranges（4.8%―9.4% for the intra-day test and 3.5%―11.9% for the inter-day test）.

Effect and Functional Mechanism of the Action of Exogenous Gibberellin on Flowering of Peach

This study was conducted to assess the effect of gibberellin and its possible mechanism of action on peach flower formation. At flower induction, 100 mg L^-1 of gibberellic acid 3 （GA3） was sprayed on the leaves of peach [Prunus persica （L.） Batsch.] cv. Bayuecui. Using anatomy, immunohistochemistry, and semi-quantitation, the in situ distribution of GAs and the expression of the key genes involved in peach flower formation in the apical meristem were studied during flowering differentiation. The results showed that induction of flowering in the Bayuecui peach occurred prior to 10 July in Beijing, China. Flower induction and further differentiation of the peach flower organs were significantly inhibited by leaf-spraying of GA3 at a concentration of 100 mg L^-1 during the induction stage. The flowering rate was only 11.67% after treatment. The distribution of GA1 in the apical meristem varied during the process of flower bud differentiation. From 13 June to 25 July, the GA1 signal from control plants was detected mainly in the vascular bundles at the base of the flower buds. No GA1 signal was detected in the apical meristem. After treatment with GA3, the distribution was similar to that of the control from 13 June to 3 July. On 13 July, a GA1 signal was detected in the apical meristem accompanied by an increase in the GA1 signal in the vascular bundles at the base of the flower buds. The GA1 signal weakened significantly in both the vascular bundles and the apical meristem on 25 July. The expression of the genes PpLEAFY and MADS6 in flower buds could be detected only on 10 October in the GA3-treated plants. The critical period for flower induction of Bayuecui peach in Beijing was in early July, during which time, leaf-spraying with 100 mg L-1 GA3 could effectively inhibit flower induction and further differentiation of the flower buds. GA1 in the gibberellin family was the suppressor for flower induction in peach. Its action was affected by the stage of flower bud differentiation. Expression of the key genes PpLEAFY and MADS6 involved in flower formation was inhibited by GA3 treatment.

Effects of Gibberellin and Ultrasonic on Seed Germination Characteristics of Different Strawberry Cultivars

Four kinds of strawberry(Benihoppe, Akihime, Tuscany and Qianmei) seeds were taken as the materials, to study the effects of gibberellin in different concentrations and ultrasonic treatment on seed germination. The results showed that thousand kernel weights of seeds from different strawberry varieties had significant difference, and the sequence was Benihoppe=Akihime>Qianmei>Tuscany. Gibberellin treatment could improve germination rate of strawberry seed, and the optimal gibberellin concentrations for Benihoppe, Tuscany, Qianmei and Akihime were 5, 5, 5 and 10 mol/L. Gibberellin treatment could improve germination potential of Tuscany and Qianmei, and germination potential rose with gibberellin concentration increased within certain range, while ultrasonic treatment obviously inhibited germination of strawberry seed.

Effect of Gibberellin,Light and Genotype on Somatic Embryogenesis and Plantlet Regeneration of Peanut

[ Objective] Peanut in vitro regeneration system was optimized to provide technical support for its genetic transformation and mutagenesis. [ Method ] The effect of gibberellin, light and genotype on somatic embryogenesis and plantiet regeneration of peanut was studied using Guihua peanut cuhivar as materials, leallets as explants, MS ＋ 10 mg/L 2, 4-D as somatic embryo induction medium, and MS ＋3 mg/L 6-BA ＋0. 8 mg/L NAA ＋ （0 - 15 mg/L） GA3 as plantlet induction me- dium. [Result]The somatic embryo induction rate of five peanut varieties under light condition of light： dark = 14 h： 10 h was significantly higher compared with that under dark condition by 7, 5 - 37.5 percent points. Among different peanut varieties, Guihua 26 represented the highest somatic embryo induction rate of 62. 8%, while Guihua 833 represented the lowest somatic embryo induction rate of 21.7%. Adding 5 - 15 mg/LGA3 in plantlet induction medium was conducive to improving the induction rate of plandets derived from somatic embryos. With addition of 5 mg/L GA3, Guihua 26 and Guihna 771 represented the highest plantlet induction rate of 42.8% and 35.3%, respectively; with addition of 15 mg/L GA3, Guihua 836, Guihua 1026 and Guihna 833 represented the highest plantlet in- duction rate of 38.7%, 33.3% and 26.4L%, respectively. Among different combinations of peanut variety and GA3 concentration, plantlet induction rate reached the highest in the combination Guihua 26 ＋ 5 mg/L CA.3 arid reached the lowest in the combination Guihua 836 ＋ 15 mg/L GA3. [ Conclusion] Appropriate light conditions are conducive to peanut somatic embryogenesis in vitro. Adding GA3 in plantlet induction medium is conducive to promoting plantlet regeneration. Guihua 26 and Guihua 836 are the best peanut varieties among the experimental genotypes for somatic embryogenesis and plant regeneration.

Seed Germination in Tomato: A Focus on Interaction between Phytochromes and Gibberellins or Abscisic Acid

Separately, it is well-documented that phytochromes (phys), gibberellin (GA) and abscisic acid (ABA) strongly control the seed germination in tomato. However, we hipothesized that phys interact with GA or ABA during this response. Thus, we make an analysis of seed germination of ABA deficient (sit), GA constitutive response (pro), phytochrome deficient (au) mutants as well as, specially, au sit and au pro double mutants of tomato?incubated in the dark or light conditions during 120 h [12 h intervals (i)]. Compared to au, which severely?reduced percentage germination (Gi%) and pro, which did not alter Gi%, au pro showed in the light enhanced Gi% and germination speed index (GSI) besides the reduced average germination time (AGT). Moreover, in the dark, germination of au pro was similar to pro. These results indicate that the mechanisms by which GA modulate germination in tomato are light dependent through the phy signaling, whereas intermediary values of Gi%, GSI and AGT in dark and light of au sit compared to au and sit single mutants indicate an additive effect of the au and sit mutations, suggesting that ABA and phy may act through the parallel signaling pathway.