Overexpression of Jatropha Gibberellin 2-oxidase 6 (JcGA2ox6) Induces Dwarfism and Smaller Leaves, Flowers and Fruits in Arabidopsis and Jatropha

Inhibition of flowering by gibberellins in the woody plant Jatropha curcas is restored by overexpression of JcFT

Jatropha curcas (J. curcas) is a perennial oil-seed plant with vigorous vegetative growth but relatively poor reproductive growth and low seed yield. Gibberellins (GAs) promotes flowering in most annual plants but inhibits flowering in many woody plants, including J. curcas. However, the underlying mechanisms of GA inhibits flowering in perennial woody plants remain unclear. Here, we found that overexpression of the GA biosynthesis gene JcGA20ox1 inhibits flowering in J. curcas and in J. curcas × J. integerrima hybrids. Consistent with this finding, overexpression of the GA catabolic gene JcGA2ox6 promotes flowering in J. curcas. qRTPCR revealed that inhibits floral transition by overexpressing JcGA20ox1 resulted from a decrease in the expression of JcFT and other flowering-related genes, which was restored by overexpressing JcFT in J. curcas. Overexpression of JcGA20ox1 or JcGA2ox6 reduced seed yield, but overexpression of JcFT significantly increased seed yield. Furthermore, hybridization experiments showed that the reduction in seed yield caused by overexpression of JcGA20ox1 or JcGA2ox6 was partially restored by the overexpression of JcFT. In addition, JcGA20ox1, JcGA2ox6 and JcFT were also found to be involved in the regulation of seed oil content and endosperm development. In conclusion, our study revealed that the inhibitory effect of GA on flowering is mediated through JcFT and demonstrated the effects of JcGA20ox1, JcGA2ox6 and JcFT on agronomic traits in J. curcas. This study also indicates the potential value of GA metabolism genes and JcFT in the breeding of new varieties of woody oil-seed plants.

Physiological and transcriptome analysis of changes in endogenous hormone and sugar content during the formation of tender asparagus stems

Asparagus is a nutritionally dense stem vegetable whose growth and development are correlated with its quality and yield. To investigate the dynamic changes and underlying mechanisms during the elongation and growth process of asparagus stems, we documented the growth pattern of asparagus and selected stem segments from four consecutive elongation stages using physiological and transcriptome analyses. Notably, the growth rate of asparagus accelerated at a length of 25 cm. A significant decrease in the concentration of sucrose, fructose, glucose, and additional sugars was observed in the elongation region of tender stems. Conversely, the levels of auxin and gibberellins(GAs) were elevated along with increased activity of enzymes involved in sucrose degradation. A significant positive correlation existed between auxin, GAs, and enzymes involved in sucrose degradation. The ABA content gradually increased with stem elongation. The tissue section showed that cell elongation is an inherent manifestation of stem elongation. The differential genes screened by transcriptome analysis were enriched in pathways such as starch and sucrose metabolism, phytohormone synthesis metabolism, and signal transduction. The expression levels of genes such as ARF, GA20ox, NCED, PIF4, and otherswere upregulated during stem elongation, while DAO, GA2ox, and other genes were downregulated. The gene expression level was consistent with changes in hormone content and influenced the cell length elongation. Additionally, the expression results of RT-qPCR were consistent with RNA-seq. The observed variations in gene expression levels, endogenous hormones and sugar changes during the elongation and growth of asparagus tender stems offer valuable insights for future investigations into the molecular mechanisms of asparagus stem growth and development and provide a theoretical foundation for cultivation and production practices.

Characterization, expression pattern, and function analysis of gibberellin oxidases in Salix matsudana

Gibberellin oxidases (GAoxs) identified from many species play indispensable roles in GA biosynthesis and GA signal transduction. However, there has been limited research conducted on the GAox family of Salix matsudana, a tetraploid ornamental tree species. Here, 54 GAox genes were identified from S. matsudana and renamed as SmGA20ox1-22, SmGA2ox1-24, SmGA3ox1-6, and SmGAox-like1/2. Gene structure and conserved motif analysis showed that SmGA3ox members possess the 1 intron and other SmGAoxs contain 2-3 introns, and motif 1/2/7 universally present in all SmGAoxs. A total of 69 gene pairs were identified from SmGAox family members, and the Ka/Ks values indicated the SmGAoxs experience the purifying selection. The intra species collinearity analysis implied S. matsudana, S. purpurea, and Populus trichocarpa have the close genetic relationship. The GO analysis suggested SmGAoxs are dominantly involved in GA metabolic process, ion binding, and oxidoreductase activity. RNA-sequencing demonstrated that some SmGAoxs may play an essential role in salt and submergence stresses. In addition, the SmGA20ox13/21 displayed the dominant vitality of GA20 oxidase, but the SmGA20ox13/21 still possessed low activities of GA2 and GA3 oxidases. This study can contribute to reveal the regulatory mechanism of salt and submergence tolerance in willow.

Gibberellin 2-Oxidases in Potato (Solanum tuberosum L.): Cloning, Characterization, In Silico Analysis and Molecular Docking

Gibberellins (GAs; tetracyclic di-terpenoid carboxylic acids) are endogenous plant growth regulators responsible for stimulating plant growth and development from seed germination to plant maturity. In potato (Solanum tuberosum L.), GA levels are known to be crucial in the complex process of tuberization. Gibberellin 2-oxidases (GA2oxs) inactivate bioactive GAs during stolon swelling and early stages of tuberization as evident from the predominant expression of a member of this gene family namely GA2ox1. We isolated and characterized a 1105-bp cDNA clone encoding a 340-aa GA2ox1 form, designated St-GA2ox1, using total RNA from growing tuber of a potato (Solanum tuberosum L.) cultivar, Kufri Chipsona-1 (KC-1) based on RT-PCR approach. A total of 26 GA2ox sequences were also retrieved from potato genome database and analysed. Multiple sequence alignment revealed sequence relatedness between the GA2oxs. Crucial protein motifs were identified. Phylogenetic analysis revealed the evolutionary relationships between the GA2oxs. Three-dimensional structure of St-GA2ox1 was predicted by using AlphaFold tool, validated by the predicted local-distance difference test and Ramachandran Plot. Structural analysis and molecular docking were carried out to identify domains, binding sites and affinity for the ligand. The STRING database and hydropathy analysis revealed the presence of a putative interaction site for other enzymes. Expression Atlas database and semi-quantitative RT-PCR revealed the expression patterns of various GA2ox forms in different potato organs. This comprehensive report would be useful in providing new insights into possible underlying mechanisms involved in tuber development, and could facilitate the targeted alteration of genes responsible to combat the stress and enhance tuber production.

JcSEUSS1 negatively regulates reproductive organ development in perennial woody Jatropha curcas

MAIN CONCLUSION

Overexpression of JcSEUSS1 resulted in late flowering, reduced flower number, wrinkled kernels, and decreased seed yield in Jatopha curcas, while downregulation of JcSEUSS1 increased flower number and seed production. The seed oil of Jatropha curcas is suitable as an ideal alternative for diesel fuel, yet the seed yield of Jatropha is restricted by its small number of female flowers and low seed setting rate. Therefore, it is crucial to identify genes that regulate flowering and seed set, and hence improve seed yield. In this study, overexpression of JcSEUSS1 resulted in late flowering, fewer flowers and fruits, and smaller fruits and seeds, causing reduced seed production and oil content. In contrast, the downregulation of JcSEUSS1 by RNA interference (RNAi) technology caused an increase in the flower number and seed yield. However, the flowering time, seed number per fruit, seed weight, and size exhibited no obvious changes in JcSEUSS1-RNAi plants. Moreover, the fatty acid composition also changed in JcSEUSS1 overexpression and RNAi plants, the percentage of unsaturated fatty acids (FAs) was increased in overexpression plants, and the saturated FAs were increased in RNAi plants. These results indicate that JcSEUSS1 played a negative role in regulating reproductive growth and worked redundantly with other genes in the regulation of flowering time, seed number per fruit, seed weight, and size.

Multi-omics reveal differentiation and maintenance of dimorphic flowers in an alpine plant on the Qinghai-Tibet Plateau

Dimorphic flowers growing on a single individual plant play a critical role in extreme adaption and reproductive assurance in plants and have high ecological and evolutionary significance. However, the omics bases underlying such a differentiation and maintenance remain largely unknown. We aimed to investigate this through genomic, transcriptome and metabolomic analyses of dimorphic flowers in an alpine biennial, Sinoswertia tetraptera (Gentianaceae). A high-quality chromosome-level genome sequence (903 Mb) was first assembled for S. tetraptera with 31,359 protein-coding genes annotated. Two rounds of recent independent whole-genome duplication (WGD) were revealed. Numerous genes from the recent species-specific WGD were found to be differentially expressed in the two types of flowers, and this may have helped contribute to the origin of this innovative trait. The genes with contrasting expressions between flowers were related to biosynthesis of hormones, floral pigments (carotenoids and flavonoids) and iridoid compounds, which are involved in both flower development and colour. Metabolomic analyses similarly suggested differential concentrations of these chemicals in the two types of flowers. The expression interactions between multiple genes may together lead to contrasting morphology and chemical concentration and open versus closed pollination of the dimorphic flowers in this species for reproductive assurance.

Functional characterization of transcriptional activator gene SIARRI in tomato reveals its role in fruit growth and ripening

Auxins regulate several characteristics of plant development and growth. Here, we characterized a new transcriptional activator SIARRI which binds specific DNA sequences and was revealed in Arabidopsis (ARR1). SIARRI acts as a two-component response regulator and its Arabidopsis homologous gene is AT3G16857. It belongs to the subfamily of type-B response regulators in the cytokinin signaling pathway. The study aimed to characterize the transgenic Micro-Tom plants by the overexpression of Solanum lycopersicum two-component response regulator ARR1. Overexpression of SIARRI results in a pleiotropic phenotype during fruit development and ripening. This study indicates that SIARRI is a primary regulator of leaf morphology and fruit development. Moreover, overexpressed plants showed variations in growth related to auxin as well as shorter hypocotyl elongation, enlarged leaf vascularization, and decreased apical dominance. The qRT-PCR investigation revealed that expression was downregulated at the breaker stage and high at Br+6 at various stages of fruit growth and ripening. In contrast to the fruit color, lycopene and β-carotene concentrations in red-yellow overexpression line fruits were reduced significantly, and also slightly reduced in some red fruits. The quantity of β-carotene in the transgenic fruits was lower than that of lycopene. This study showed that this gene might be a new transcriptional activator in fruit development and ripening. Furthermore, this study will provide new insights into tomato fruit ripening.

Fruit shape loci sun, ovate, fs8.1 and their interactions affect seed size and shape in tomato

Seed size and shape are not only critical for plant reproduction and dispersal, but also important agronomic traits. Tomato fruit shape loci sun, ovate and fs8.1 regulate the morphology of fruit, flower, leaf and stem, and recently their functions in seed morphogenesis have also been noticed. However, mechanism underlying seed morphology variation has not been systematically investigated yet. Thus, using the near isogenic lines (NILs) harboring one, two or three of the fruit shape loci, histological, physiological and transcriptional bases of seed morphology change have been studied. sun and ovate showed potential abilities in decreasing seed size, whereas, fs8.1 had a potential ability in increasing this parameter. Interactions between two loci and the interaction among three loci all led to significant decrease of seed size. All the loci significantly down-regulated seed shape index (SSI), except for sun/fs8.1 double NIL, which resulted in the reductions in both seed length and width and finally led to a decreased trend of SSI. Histologically, seed morphological changes were mainly attributed to the cell number variations. Transcriptional and physiological analyses discovered that phytohormone-, cytoskeleton- as well as sugar transportation- and degradation-related genes were involved in the regulation of seed morphology by the fruit shape loci.

Exogenous Phytohormones and Fertilizers Enhance Jatropha curcas L. Growth through the Regulation of Physiological, Morphological, and Biochemical Parameters

Jatropha curcas L. is a perennial plant, that emerged as a biodiesel crop attracting the great interest of researchers. However, it is considered a semi-wild plant and needed to apply crop-improving practices to enhance its full yield potential. This study was conducted to improve the growth and development of the J. curcas plant by exogenous application of Gibberellic acid (GA), indole acetic acid (IAA), and fertilizer (nitrogen, phosphorus, potassium (NPK)). The experiment was conducted in pots in triplicate and 100 ppm and 250 ppm of GA and IAA were applied separately while NPK was applied in two levels (30 and 60 g/pot). The results revealed a significant difference in growth parameters with the application of hormones and fertilizer. The highest shoot length (47%), root length (63%), root fresh weight (72%), and root dry weight (172%) were shown by plants treated with GA 250 ppm. While plants treated with NPK 60 g showed the highest increases in shoot fresh weight and shoot dry weight compared to control plants. The highest increase in leaves number (274%) and branches number (266%) were shown by the plants treated with GA 100 ppm and GA 250 ppm, respectively, while GA 250 ppm and IAA 250 ppm highly increased stem diameter (123%) and stem diameter was also shown by GA 250 ppm-treated plants. NPK 60 g highly increased proximate composition (protein content, carbohydrate, fat, moisture content, and ash content) compare with hormones and control plants. Our results concluded the optimized concentration of IAA, GA, and NPK significantly increases J. curcas growth vigor.

PavGA2ox-2L inhibits the plant growth and development interacting with PavDWARF in sweet cherry (Prunus avium L.)

Dwarf dense planting is helpful to improve the yield and quality of sweet cherry, which has enormous market demand. GA2oxs (GA oxidases) affect plant height, dormancy release, flower development, and seed germination by participating in the metabolic regulation and signal transduction of GA (Gibberellin). However, the research on GA2ox in sweet cherry is little and worthy of further investigation. Therefore, we identified the PavGA2ox-2L gene from sweet cherry, close to PynGA2ox-2 from Prunus yedoensis var. Nudiflora. The phylogenetic analysis indicated conserved functions with these evolutionarily closer GA2ox subfamily genes. Subcellular localization forecast analysis indicated that PavGA2ox-2L was localized in the nucleus or cytoplasm. The expression levels of PavGA2ox-2L were higher in winter, indicating that PavGA2ox-2L promoted maintained flower bud dormancy. The expression levels of PavGA2ox-2L were significantly increased after GA₄₊₇ treatment while decreased after GR24 (a synthetic analog of SLs (Strigolactones)) or TIS108 (a triazole-type SL-biosynthesis inhibitor) treatments. Over-expression of PavGA2ox-2L resulted in decreased plant height, delayed flowering time, and low seed germination rate in Arabidopsis thaliana. Furthermore, the interaction between PavGA2ox-2L and PavDWARF was verified by Y2H and BiFC assays. In the current investigation, PavGA2ox-2L functions as a GA metabolic gene that promotes dwarf dense planting, delays flowering time, and inhibits seed germination. In addition, it also participates in regulating plant growth and development through the interaction with the critical negative regulator PavDWARF of Gibberellin. These results will help us better explore the molecular mechanism of GA2ox-mediated dwarf and late-maturing varieties for fruit trees.

Pivotal Role of Phytohormones and Their Responsive Genes in Plant Growth and Their Signaling and Transduction Pathway under Salt Stress in Cotton

The presence of phyto-hormones in plants at relatively low concentrations plays an indispensable role in regulating crop growth and yield. Salt stress is one of the major abiotic stresses limiting cotton production. It has been reported that exogenous phyto-hormones are involved in various plant defense systems against salt stress. Recently, different studies revealed the pivotal performance of hormones in regulating cotton growth and yield. However, a comprehensive understanding of these exogenous hormones, which regulate cotton growth and yield under salt stress, is lacking. In this review, we focused on new advances in elucidating the roles of exogenous hormones (gibberellin (GA) and salicylic acid (SA)) and their signaling and transduction pathways and the cross-talk between GA and SA in regulating crop growth and development under salt stress. In this review, we not only focused on the role of phyto-hormones but also identified the roles of GA and SA responsive genes to salt stress. Our aim is to provide a comprehensive review of the performance of GA and SA and their responsive genes under salt stress, assisting in the further elucidation of the mechanism that plant hormones use to regulate growth and yield under salt stress.

AmCBF1 Transcription Factor Regulates Plant Architecture by Repressing GhPP2C1 or GhPP2C2 in Gossypium hirsutum

Dwarfism is a beneficial trait in many crops. Dwarf crops hold certain advantages over taller crops in lodging resistance, fertilizer tolerance, and yield. Overexpression of CBF/DREB transcription factors can lead to dwarfing in many plant species, but the molecular mechanism of plant dwarfing caused by overexpression of CBF/DREB in upland cotton (Gossypium hirsutum) remains unclear. In this study, we observed that overexpression of the Ammopiptanthus mongolicus AmCBF1 transcription factor in upland cotton R15 reduced plant height, whereas virus-induced gene silencing of AmCBF1 in the derived dwarf lines L28 and L30 partially restored plant height. Five protein phosphatase (PP2C) genes (GhPP2C1 to GhPP2C5) in cotton were identified by RNA-sequencing among genes differentially expressed in L28 or L30 in comparison with R15 and thus may play an important role in AmCBF1-regulated dwarfing in cotton. Gene expression analysis showed that the GhPP2C genes were down-regulated significantly in L28 and L30, and silencing of GhPP2C1 or GhPP2C2 in R15 inhibited the growth of cotton seedlings. Subcellular localization assays revealed that GhPP2C1 was localized to the cell membrane and nucleus, whereas GhPP2C2 was exclusively localized to the nucleus. Yeast one-hybrid and dual-luciferase assays showed that AmCBF1 was able to bind to the CRT/DRE elements of the upstream promoter of GhPP2C1 or GhPP2C2 and repress their expression. These findings provide insight into the mechanism of dwarfing and may contribute to the breeding of dwarf cultivars of upland cotton.

An ortholog of the MADS-box gene SEPALLATA3 regulates stamen development in the woody plant Jatropha curcas

Overexpression of JcSEP3 causes defective stamen development in Jatropha curcas, in which brassinosteroid and gibberellin signaling pathways may be involved. SEPALLATAs (SEPs), the class E genes of the ABCE model, are required for floral organ determination. In this study, we investigated the role of the JcSEP3 gene in floral organ development in the woody plant Jatropha curcas. Transgenic Jatropha plants overexpressing JcSEP3 displayed abnormal phenotypes such as deficient anthers and pollen, as well as free stamen filaments, whereas JcSEP3-RNA interference (RNAi) transgenic plants had no obvious phenotypic changes, suggesting that JcSEP3 is redundant with other JcSEP genes in Jatropha. Moreover, we compared the transcriptomes of wild-type plants, JcSEP3-overexpressing, and JcSEP3-RNAi transgenic plants. In the JcSEP3-overexpressing transgenic plants, we discovered 25 upregulated genes involved in anther and pollen development, as well as 12 induced genes in brassinosteroid (BR) and gibberellin (GA) signaling pathways. These results suggest that JcSEP3 directly or indirectly regulates stamen development, concomitant with the regulation of BR and GA signaling pathways. Our findings help to understand the roles of SEP genes in stamen development in perennial woody plants.

Pepper Fruit Elongation Is Controlled by Capsicum annuum Ovate Family Protein 20

Fruit shape is one of the most important quality traits of pepper (Capsicum spp.) and is used as a major attribute for the classification of fruit types. Wide natural variation in fruit shape exists among the major cultivated species Capsicum annuum, allowing the identification of several QTLs controlling the trait. However, to date, no genes underlying fruit shape QTLs have been conclusively identified, nor has their function been verified in pepper. We constructed a mapping population from a cross of round- and elongated-fruited C. annuum parents and identified a single major QTL on chromosome 10, termed fs10, explaining 68 and 70% of the phenotypic variation for fruit shape index and for distal fruit end angle, respectively. The QTL was mapped in several generations and was localized to a 5 Mbp region containing the ortholog of SlOFP20 that suppresses fruit elongation in tomato. Virus-induced gene silencing of the pepper ortholog CaOFP20 resulted in increased fruit elongation on two independent backgrounds. Furthermore, CaOFP20 exhibited differential expression in fs10 near-isogenic lines, as well as in an association panel of elongated- and round-fruited accessions. A 42-bp deletion in the upstream region of CaOFP20 was most strongly associated with fruit shape variation within the locus. Histological observations in ovaries and fruit pericarps indicated that fs10 exerts its effect on fruit elongation by controlling cell expansion and replication. Our results indicate that CaOFP20 functions as a suppressor of fruit elongation in C. annuum and is the most likely candidate gene underlying fs10.

Characterization of the molecular mechanism underlying the dwarfism of dsh mutant watermelon plants

Developing dwarf watermelon is a major objective among breeders. The dsh dwarf watermelon germplasm developed in our laboratory is genetically stable. We previously produced preliminary evidence that Cla010726, which encodes a gibberellin 20-oxidase-like protein, is the primary gene controlling dwarfism in watermelon. However, the underlying genetic mechanism was unknown. In this study, we characterized the spontaneous recessive mutant dsh, which is a gibberellin (GA)-deficient mutant. Many of the phenotypic traits of dsh plants are similar to those of known GA-deficient mutants. The dsh plants were sensitive to exogenous bioactive GAs, which increased seedling height. Moreover, a quantitative analysis of endogenous GA₃ proved that the bioactive GA₃ content was substantially lower than normal in dsh. Additionally, the T₅ClaGA20ox RNAi plants generally exhibited dwarfism, with short stems and internodes as well as small leaves and fruit. An examination of the transgenic plants carrying the ClaGA20ox1 promoter-GUS and mutant ClaGA20ox2 promoter-GUS constructs confirmed that two promoter sites are involved in the regulation of ClaGA20ox expression. Hence, mutations in the promoter of the GA20ox gene, which encodes a key enzyme involved in gibberellin biosynthesis, lead to the dwarfism of watermelon plants. The dsh mutant is a potentially useful germplasm resource for developing new watermelon varieties exhibiting dwarfism.

Phenotypic Characterization and Differential Gene Expression Analysis Reveal That Dwarf Mutant dwf Dwarfism Is Associated with Gibberellin in Eggplant

Dwarfism is a desirable trait in eggplant breeding, as it confers higher lodging resistance and allows simplified management and harvest. However, a few dwarf mutants have been reported, and the molecular mechanism underlying dwarfism in eggplant is completely unknown. Here, we report a dwarf mutant (dwf) isolated from an ethyl methyl sulfonate (EMS)-induced mutant library. The hypocotyl length, plant height, and length of internode cells of dwf were significantly decreased compared to those of the wild-type parent ‘14-345’ (WT). Differential gene expression analysis revealed that GA-related genes, including GA2ox and DELLA, were up-regulated whereas the gibberellin (GA3) content decreased in dwf. Moreover, exogenous GA3 treatment significantly increased the relative growth rate of dwf compared to WT, further indicating the important roles of GA in regulating the dwarf phenotype of dwf. Collectively, our findings shed light on GA-mediated dwarfism in dwf plants and offer a good germplasm that could be used for eggplant dwarfism breeding in the future.

Genome-wide analysis of gibberellin-dioxygenases gene family and their responses to GA applications in maize

Gibberellin-dioxygenases genes plays important roles in the regulating plant development. However, Gibberellin-dioxygenases genes are rarely reported in maize, especially response to gibberellin (GA). In present study, 27 Gibberellin-dioxygenases genes were identified in the maize and they were classified into seven subfamilies (I-VII) based on phylogenetic analysis. This result was also further confirmed by their gene structure and conserved motif characteristics. And gibberellin-dioxygenases genes only occurred segmental duplication that occurs most frequently in plants. Furthermore, the gibberellin-dioxygenases genes showed different tissue expression pattern in different tissues and most of the gibberellin-dioxygenases genes showed tissue specific expression. Moreover, almost all the gibberellin-dioxygenases genes were significantly elevated in response to GA except for ZmGA2ox2 and ZmGA20ox10 of 15 gibberellin-dioxygenases genes normally expressed in leaves while 10 and 11 gibberellin-dioxygenases genes showed up and down regulated under GA treatment than that under normal condition in leaf sheath. In addition, we found that ZmGA2ox1, ZmGA2ox4, ZmGA20ox7, ZmGA3ox1 and ZmGA3ox3 might be potential genes for regulating balance of GAs which play essential roles in plant development. These findings will increase our understanding of Gibberellin-dioxygenases gene family in response to GA and will provide a solid base for further functional characterization of Gibberellin-dioxygenases genes in maize.

Functional Analysis of the Gibberellin 2-oxidase Gene Family in Peach

Peach (Prunus persica L. Batsch) trees grow vigorously and are subject to intense pruning during orchard cultivation. Reducing the levels of endogenous gibberellins (GAs) represents an effective method for controlling branch growth. Gibberellin 2-oxidases (GA2oxs) deactivate bioactive GAs, but little is known about the GA2ox gene family in peach. In this study, we identified seven PpGA2ox genes in the peach genome, which were clustered into three subgroups: C₁₉-GA2ox-I, C₁₉-GA2ox-II, and C₂₀-GA2ox-I. Overexpressing representative genes from the three subgroups, PpGA2ox-1, PpGA2ox-5, and PpGA2ox-2, in tobacco resulted in dwarf plants with shorter stems and smaller leaves than the wild type. An analysis of the GA metabolic profiles of the transgenic plants showed that PpGA2ox-5 (a member of subgroup C₁₉-GA2ox-II) is simultaneously active against both C₁₉-GAs and C₂₀-GAs,which implied that C₁₉-GA2ox-II enzymes represent intermediates of C₁₉-GA2oxs and C₂₀-GA2oxs. Exogenous GA₃ treatment of shoot tips activated the expression of all seven PpGA2ox genes, with different response times: the C ₁₉-GA2ox genes were transcriptionally activated more rapidly than the C₂₀-GA2ox genes. GA metabolic profile analysis suggested that C₂₀-GA2ox depletes GA levels more broadly than C₁₉-GA2ox. These results suggest that the PpGA2ox gene family is responsible for fine-tuning endogenous GA levels in peach. Our findings provide a theoretical basis for appropriately controlling the vigorous growth of peach trees.

Plant buffering against the high-light stress-induced accumulation of CsGA2ox8 transcripts via alternative splicing to finely tune gibberellin levels and maintain hypocotyl elongation

In plants, alternative splicing (AS) is markedly induced in response to environmental stresses, but it is unclear why plants generate multiple transcripts under stress conditions. In this study, RNA-seq was performed to identify AS events in cucumber seedlings grown under different light intensities. We identified a novel transcript of the gibberellin (GA)-deactivating enzyme Gibberellin 2-beta-dioxygenase 8 (CsGA2ox8). Compared with canonical CsGA2ox8.1, the CsGA2ox8.2 isoform presented intron retention between the second and third exons. Functional analysis proved that the transcript of CsGA2ox8.1 but not CsGA2ox8.2 played a role in the deactivation of bioactive GAs. Moreover, expression analysis demonstrated that both transcripts were upregulated by increased light intensity, but the expression level of CsGA2ox8.1 increased slowly when the light intensity was >400 µmol·m^-2·s^-1 PPFD (photosynthetic photon flux density), while the CsGA2ox8.2 transcript levels increased rapidly when the light intensity was >200 µmol·m^-2·s^-1 PPFD. Our findings provide evidence that plants might finely tune their GA levels by buffering against the normal transcripts of CsGA2ox8 through AS.

Systematic Analysis of Gibberellin Pathway Components in Medicago truncatula Reveals the Potential Application of Gibberellin in Biomass Improvement

Gibberellins (GAs), a class of phytohormones, act as an essential natural regulator of plant growth and development. Many studies have shown that GA is related to rhizobial infection and nodule organogenesis in legume species. However, thus far, GA metabolism and signaling components are largely unknown in the model legume Medicago truncatula. In this study, a genome-wide analysis of GA metabolism and signaling genes was carried out. In total 29 components, including 8 MtGA20ox genes, 2 MtGA3ox genes, 13 MtGA2ox genes, 3 MtGID1 genes, and 3 MtDELLA genes were identified in M. truncatula genome. Expression profiles revealed that most members of MtGAox, MtGID1, and MtDELLA showed tissue-specific expression patterns. In addition, the GA biosynthesis and deactivation genes displayed a feedback regulation on GA treatment, respectively. Yeast two-hybrid assays showed that all the three MtGID1s interacted with MtDELLA1 and MtDELLA2, suggesting that the MtGID1s are functional GA receptors. More importantly, M. truncatula exhibited increased plant height and biomass by ectopic expression of the MtGA20ox1, suggesting that enhanced GA response has the potential for forage improvement.

Genome-wide identification, characterization and expression profiling of gibberellin metabolism genes in jute

BACKGROUND

Gibberellin (GA) is one of the most essential phytohormones that modulate plant growth and development. Jute (Corchorus sp.) is the second most important source of bast fiber. Our result has shown that exogenous GA can positively regulate jute height and related characteristics which mean increasing endogenous GA production will help to get a jute variety with improved characteristics. However, genes involved in jute GA biosynthesis have not been analyzed precisely.

RESULTS

Genome-wide analysis identified twenty-two candidate genes involved in jute GA biosynthesis pathway. Among them, four genes- CoCPS, CoKS, CoKO and CoKAO work in early steps. Seven CoGA20oxs, three CoGA3oxs, and eight GA2oxs genes work in the later steps. These genes were characterized through phylogenetic, motif, gene structure, and promoter region analysis along with chromosomal localization. Spatial gene expression analysis revealed that 11 GA oxidases were actively related to jute GA production and four of them were marked as key regulators based on their expression level. All the biosynthesis genes both early and later steps showed tissue specificity. GA oxidase genes were under feedback regulation whereas early steps genes were not subject to such regulation.

CONCLUSION

Enriched knowledge about jute GA biosynthesis pathway and genes will help to increase endogenous GA production in jute by changing the expression level of key regulator genes. CoGA20ox7, CoGA3ox2, CoGA2ox3, and CoGA2ox5 may be the most important genes for GA production.

Molecular Mechanisms of the Floral Biology of Jatropha curcas: Opportunities and Challenges as an Energy Crop

Fossil fuel sources are a limited resource and could eventually be depleted. Biofuels have emerged as a renewable alternative to fossil fuels. Jatropha has grown in significance as a potential bioenergy crop due to its high content of seed oil. However, Jatropha's lack of high-yielding seed genotypes limits its potential use for biofuel production. The main cause of lower seed yield is the low female to male flower ratio (1:25-10), which affects the total amount of seeds produced per plant. Here, we review the genetic factors responsible for floral transitions, floral organ development, and regulated gene products in Jatropha. We also summarize potential gene targets to increase seed production and discuss challenges ahead.

A Lobularia maritima LmSAP protein modulates gibberellic acid homeostasis via its A20 domain under abiotic stress conditions

Stress-associated proteins (SAPs) are favorable targets to improve stress tolerance in plants, owing to their roles in developmental processes and stress responses. However, the role of SAPs and the molecular mechanisms by which they regulate plant stress responses remain poorly understood. Previously, it was reported that LmSAP expression was upregulated by various abiotic stressors in Lobularia maritima, and that transgenic tobacco lines with constitutively expressed LmSAPΔA20 and LmSAPΔA20-ΔAN1 showed dwarf phenotypes due to the deficiency of cell elongation under salt and osmotic stresses. In this study, we examined the function of A20 domain in the GA pathway in response to abiotic stresses. Transient expression of acGFP-LmSAPΔA20 and acGFP-LmSAPΔA20-ΔAN1 in onion epidermal cells demonstrated that these fused proteins were localized in the nucleo–cytoplasm. However, the truncated form acGFP-LmSAPΔAN1 was localized in the nucleus. Moreover, comparison of native and truncated LmSAP showed dramatic structural changes caused by the deletion of the A20 domain, leading to loss of function and localization. Interestingly, overexpression LmSAP and truncated LmSAPΔAN1 led to up-regulation of GA biosynthetic genes and increased total gibberellins (GAs) content, corresponding with accelerated development in transgenic tobacco plants. Moreover, the dwarf phenotype of the transgenic lines that express LmSAPΔA20 and LmSAPΔA20-ΔAN1 under stress conditions was fully restored by the application of exogenous GA₃. These findings improve our understanding of the role of LmSAP in regulating GA homeostasis, which is important for regulating plant development under abiotic stress conditions.

Dual Role of Gibberellin in Perennial Shoot Branching: Inhibition and Activation

Shoot branching from axillary buds (AXBs) is regulated by a network of inhibitory and promotive forces, which includes hormones. In perennials, the dwarfed stature of the embryonic shoot inside AXBs is indicative of gibberellin (GA) deficiency, suggesting that AXB activation and outgrowth require GA. Nonetheless, the role of GA in branching has remained obscure. We here carried out comprehensive GA transcript and metabolite analyses in hybrid aspen, a perennial branching model. The results indicate that GA has an inhibitory as well as promotive role in branching. The latter is executed in two phases. While the expression level of GA2ox is high in quiescent AXBs, decapitation rapidly downregulated it, implying increased GA signaling. In the second phase, GA3ox2-mediated de novo GA-biosynthesis is initiated between 12 and 24 h, prior to AXB elongation. Metabolite analyzes showed that GA_1/4 levels were typically high in proliferating apices and low in the developmentally inactive, quiescent AXBs, whereas the reverse was true for GA_3/6. To investigate if AXBs are differently affected by GA₃, GA₄, and GR24, an analog of the branch-inhibitor hormone strigolactone, they were fed into AXBs of single-node cuttings. GA₃ and GA₄ had similar effects on GA and SL pathway genes, but crucially GA₃ induced AXB abscission whereas GA₄ promoted outgrowth. Both GA₃ and GA₄ strongly upregulated GA2ox genes, which deactivate GA_1/4 but not GA_3/6. Thus, the observed production of GA_3/6 in quiescent AXBs targets GA_1/4 for GA2ox-mediated deactivation. AXB quiescence can therefore be maintained by GA_3/6, in combination with strigolactone. Our discovery of the distinct tasks of GA₃ and GA₄ in AXB activation might explain why the role of GA in branching has been difficult to decipher. Together, the results support a novel paradigm in which GA_3/6 maintains high levels of GA2ox expression and low levels of GA₄ in quiescent AXBs, whereas activation and outgrowth require increased GA_1/4 signaling through the rapid reduction of GA deactivation and subsequent GA biosynthesis.

Comprehensive expression analysis of Arabidopsis GA2-oxidase genes and their functional insights

Bioactive gibberellins (GAs) play multiple roles in plant development and stress responses. GA2-oxidases (GA2oxs) are a class of 2-oxoglutarate-dependent dioxygenases that regulate the deactivation of bioactive GAs. In this study, we investigated the phylogeny and domain structures of the seven GA2ox genes present in the Arabidopsis thaliana genome. Comprehensive expression analysis using translational reporter lines showed that the seven GA2ox genes are differentially expressed during Arabidopsis growth and development: GA2ox1 is specifically expressed in the hypocotyl and lateral root primordium; GA2ox2 is highly expressed in aboveground tissues; GA2ox3 is expressed in the chalazal endosperm of the early embryo sac and inflorescences; GA2ox4 is expressed in the shoot apical meristem and during lateral root initiation; GA2ox6 is expressed in the maturation zone, but not in the meristem or elongating zone of the root; GA2ox7 is constitutively expressed during almost all developmental stages; and GA2ox8 is exclusively expressed in stomatal cells. Overexpression of each of these GA2ox genes inhibited high temperature-induced hypocotyl elongation in both wild-type and elongated hypocotyl 5 plants, which have an elongated hypocotyl phenotype, suggesting that these genes negatively regulate hypocotyl elongation by reducing bioactive GA levels. This study provides a valuable resource for further elucidating the roles of GA2ox genes during different stages of development.

Genome-wide analysis of spatiotemporal gene expression patterns during floral organ development in Brassica rapa

Flowering is a key agronomic trait that directly influences crop yield and quality and serves as a model system for elucidating the molecular basis that controls successful reproduction, adaptation, and diversification of flowering plants. Adequate knowledge of continuous series of expression data from the floral transition to maturation is lacking in Brassica rapa. To unravel the genome expression associated with the development of early small floral buds (< 2 mm; FB2), early large floral buds (2-4 mm; FB4), stamens (STs) and carpels (CPs), transcriptome profiling was carried out with a Br300K oligo microarray. The results showed that at least 6848 known nonredundant genes (30% of the genes of the Br300K) were differentially expressed during the floral transition from vegetative tissues to maturation. Functional annotation of the differentially expressed genes (DEGs) (fold change ≥ 5) by comparison with a close relative, Arabidopsis thaliana, revealed 6552 unigenes (4579 upregulated; 1973 downregulated), including 131 Brassica-specific and 116 functionally known floral Arabidopsis homologs. Additionally, 1723, 236 and 232 DEGs were preferentially expressed in the tissues of STs, FB2, and CPs. These DEGs also included 43 transcription factors, mainly AP2/ERF-ERF, NAC, MADS-MIKC, C2H2, bHLH, and WRKY members. The differential gene expression during flower development induced dramatic changes in activities related to metabolic processes (23.7%), cellular (22.7%) processes, responses to the stimuli (7.5%) and reproduction (1%). A relatively large number of DEGs were observed in STs and were overrepresented by photosynthesis-related activities. Subsequent analysis via semiquantitative RT-PCR, histological analysis performed with in situ hybridization of BrLTP1 and transgenic reporter lines (BrLTP promoter::GUS) of B. rapa ssp. pekinensis supported the spatiotemporal expression patterns. Together, these results suggest that a temporally and spatially regulated process of the selective expression of distinct fractions of the same genome leads to the development of floral organs. Interestingly, most of the differentially expressed floral transcripts were located on chromosomes 3 and 9. This study generated a genome expression atlas of the early floral transition to maturation that represented the flowering regulatory elements of Brassica rapa.

Ectopic Expression of Jatropha curcas TREHALOSE-6-PHOSPHATE PHOSPHATASE J Causes Late-Flowering and Heterostylous Phenotypes in Arabidopsis but not in Jatropha

Trehalose-6-phosphate (T6P) phosphatase (TPP), a dephosphorylating enzyme, catalyzes the dephosphorylation of T6P, generating trehalose. In Jatropha, we found six members of the TPP family. Five of them JcTPPA, JcTPPC, JcTPPD, JcTPPG, and JcTPPJ are highly expressed in female flowers or male flowers, or both, suggesting that members of the JcTPP family may participate in flower development in Jatropha. The wide expression of JcTPPJ gene in various organs implied its versatile roles and thus was chosen for unraveling its biological functions during developmental process. We constructed an overexpression vector of JcTPPJ cDNA driven by the cauliflower mosaic virus (CaMV) 35S promoter for genetic transformation. Compared with control Arabidopsis plants, 35S:JcTPPJ transgenic Arabidopsis plants presented greater sucrose contents in their inflorescences and displayed late-flowering and heterostylous phenotypes. Exogenous application of sucrose to the inflorescence buds of wild-type Arabidopsis repressed the development of the perianth and filaments, with a phenocopy of the 35S:JcTPPJ transgenic Arabidopsis. These results suggested that the significantly increased sucrose level in the inflorescence caused (or induced) by JcTTPJ overexpression, was responsible for the formation of heterostylous flower phenotype. However, 35S:JcTPPJ transgenic Jatropha displayed no obvious phenotypic changes, implying that JcTPPJ alone may not be sufficient for regulating flower development in Jatropha. Our results are helpful for understanding the function of TPPs, which may regulate flower organ development by manipulating the sucrose status in plants.

The HDA19 histone deacetylase complex is involved in the regulation of flowering time in a photoperiod-dependent manner

Chromatin modifications are known to affect flowering time in plants, but little is known about how these modifications regulate flowering time in response to environmental signals like photoperiod. In Arabidopsis thaliana, HDC1, a conserved subunit of the RPD3-like histone deacetylase (HDAC) complex, was previously reported to regulate flowering time via the same mechanism as does the HDAC HDA6. Here, we demonstrate that HDC1, SNLs and MSI1 are shared subunits of the HDA6 and HDA19 HDAC complexes. While the late-flowering phenotype of the hda6 mutant is independent of photoperiod, the hda19, hdc1 and snl2/3/4 mutants flower later than or at a similar time to the wild-type in long-day conditions but flower earlier than the wild-type in short-day conditions. Our genome-wide analyses indicate that the effect of hdc1 on histone acetylation and transcription is comparable with that of hda19 but is different from that of hda6. Especially, we demonstrate that the HDA19 complex directly regulates the expression of two flowering repressor genes related to the gibberellin signaling pathway. Thus, the study reveals a photoperiod-dependent role of the HDA19 HDAC complex in the regulation of flowering time.

The Complex Interactions Between Flowering Behavior and Fiber Quality in Hemp

Hemp, Cannabis sativa L., is a sustainable multipurpose fiber crop with high nutrient and water use efficiency and with biomass of excellent quality for textile fibers and construction materials. The yield and quality of hemp biomass are largely determined by the genetic background of the hemp cultivar but are also strongly affected by environmental factors, such as temperature and photoperiod. Hemp is a facultative short-day plant, characterized by a strong adaptation to photoperiod and a great influence of environmental factors on important agronomic traits such as "flowering-time" and "sex determination." This sensitivity of hemp can cause a considerable degree of heterogeneity, leading to unforeseen yield reductions. Fiber quality for instance is influenced by the developmental stage of hemp at harvest. Also, male and female plants differ in stature and produce fibers with different properties and quality. Next to these causes, there is evidence for specific genotypic variation in fiber quality among hemp accessions. Before improved hemp cultivars can be developed, with specific flowering-times and fiber qualities, and adapted to different geographical regions, a better understanding of the molecular mechanisms controlling important phenological traits such as "flowering-time" and "sex determination" in relation to fiber quality in hemp is required. It is well known that genetic factors play a major role in the outcome of both phenological traits, but the major molecular factors involved in this mechanism are not characterized in hemp. Genome sequences and transcriptome data are available but their analysis mainly focused on the cannabinoid pathway for medical purposes. Herein, we review the current knowledge of phenotypic and genetic data available for "flowering-time," "sex determination," and "fiber quality" in short-day and dioecious crops, respectively, and compare them with the situation in hemp. A picture emerges for several controlling key genes, for which natural genetic variation may lead to desired flowering behavior, including examples of pleiotropic effects on yield quality and on carbon partitioning. Finally, we discuss the prospects for using this knowledge for the molecular breeding of this sustainable crop via a candidate gene approach.

Differential gene expression between the vigorous and dwarf litchi cultivars based on RNA-Seq transcriptome analysis

Litchi (Litchi chinesis Sonn.) is the most economically significant member of Sapindaceae family, especially in sub-tropical regions. However, its tall tree body often brings many inconveniences to production management. In order to modify the tree size or growth for productivity optimization and simplifying management, it is urgent to reveal the dwarf mechanism of litchi for dwarfing rootstocks or cultivar breeding. However, to date, the mechanisms on litchi dwarfism is still poor known. In the present study, transcriptome profiling were performed on L. chinensis cv. 'Feizixiao' (FZX, vigorous cultivar) and 'Ziniangxi' (ZNX, dwarf cultivar). A total of 55,810 unigenes were obtained, and 9,190 unigenes were differentially expressed between vigorous and dwarf litchi samples. Gene functional enrichment analysis indicated that the differentially expressed unigenes (DEGs) were related to phytohormone metabolism and signal transduction, and energy metabolism pathways. In particular, GA2ox were only up-regulated in ZNX samples, indicating GA might play an important role in regulating huge difference between vigorous and dwarf litchi cultivars. In addition, the 35S::LcGA2ox transgenic tobacco plants were dwarf and had smaller leaves or branches than wild type plants. Our study provided a series of candidate genes to reveal the mechanism of litchi dwarf.

Analysis of Transcriptional Responses of the Inflorescence Meristems in Jatropha curcas Following Gibberellin Treatment

Jatropha curcas L. seeds an oilseed plant with great potential for biodiesel production. However, low seed yield, which was limited by its lower female flowers, was a major drawback for its utilization. Our previous study found that the flower number and female-to-male ratio were increased by gibberellin treatment. Here, we compared the transcriptomic profiles of inflorescence meristem at different time points after gibberellic acid A3 (GA₃) treatment. The present study showed that 951 differentially expressed genes were obtained in response to gibberellin treatment, compared with control samples. The 6-h time point was an important phase in the response to exogenous gibberellin. Furthermore, the plant endogenous gibberellin, auxin, ethylene, abscisic acid, and brassinolide-signaling transduction pathways were repressed, whereas the genes associated with cytokinin and jasmonic acid signaling were upregulated for 24-h time point following GA₃ treatment. In addition, the floral meristem determinacy genes (JcLFY, JcSOC1) and floral organ identity genes (JcAP3, JcPI, JcSEP1-3) were significantly upregulated, but their negative regulator (JcSVP) was downregulated after GA₃ treatment. Moreover, the effects of phytohormone, which was induced by exogenous plant growth regulator, mainly acted on the female floral differentiation process. To the best of our knowledge, this data is the first comprehensive analysis of the underlying transcriptional response mechanism of floral differentiation following GA₃ treatment in J. curcas, which helps in engineering high-yielding varieties of Jatropha.