Gibberellin Biosynthesis Research Articles

Pleiotropic Effect of GNP1 Underlying Grain Number per Panicle on Sink, Source and Flow in Rice.

Rice yield potential is largely determined by the balance among source capacity, sink strength, and flow fluency. Our previous study indicated that the gene GNP1 encoding gibberellin biosynthesis gene GA20ox1 affects grain number per panicle (GNP) in rice, thus resulting in increase of grain yield. To clarify GNP1 effect on sink, source and flow in regulating rice grain yield, we compared Lemont, a japonica (geng) cultivar, with its near-isogenic line (NIL-GNP1TQ) in Lemont background with introgression of the allele at GNP1 from Teqing, a high-yielding indica (xian) cultivar. NIL-GNP1TQ exhibited averagely 32.8% more GNP than Lemont with the compensation by reduced seed setting rate, panicle number and single-grain weight. However, NIL-GNP1TQ still produced averagely 7.2% higher grain yield than Lemont in two years, mainly attributed to significantly more filled grain number per panicle, and greater vascular system contributing to photoassimilates transport to spikelets. The significantly decreased grain weight of superior spikelets (SS) in NIL-GNP1TQ was ascribed to a significant decrease of grain size while the significantly decreased grain weight of inferior spikelets (IS) ascribed to both grain size and poor grain-filling as compared with Lemont. The low activities of key enzymes of carbon metabolism might account for the poor grain-filling in IS, which resulted in more unfilled grains or small grain bulk density in NIL-GNP1TQ. In addition, low seed setting rate and grain weight of IS in NIL-GNP1TQ might be partially resulted from significantly lower carbohydrate accumulation in culms and leaf sheath before heading compared with Lemont. Our results indicated that significantly increased GNP from introgression of GNP1TQ into Lemont did not highly significantly improve grain yield of NIL-GNP1TQ as expected, due primarily to significant low sink activities in IS and possible insufficient source supply which didn’t fully meet the increased sink capacity. The results provided useful information for improving rice yield potential through reasonably introgressing or pyramiding the favorable alleles underlying source-related or panicle number traits by marker-assisted selection.

Identification and genetic analysis of qCL1.2, a novel allele of the \u201cgreen revolution\u201d gene SD1 from wild rice (Oryza rufipogon) that enhances plant height

BackgroundThe exploitation of novel alleles from wild rice that were lost during rice cultivation could be very important for rice breeding and evolutionary studies. Plant height (PH) was a target of artificial selection during rice domestication and is still a target of modern breeding. The “green revolution” gene semi-dwarf 1 (SD1) were well documented and used in the past decades, allele from wild rice could provide new insights into the functions and evolution of this gene.ResultsWe identified a PH-related quantitative trait locus, qCL1.2,from wild riceusing a set of chromosome segment substitution lines. qCL1.2encodesa novel allele of SD1 gene. The wild allele of SD1 is a dominant locus that can significantly promote rice internode length by regulating the expression levels of genes involved in gibberellin biosynthesis and signal transduction. Nucleotide diversity and haplotype network analyses of the SD1 gene were performed using 2822 rice landraces. Two previously reported functional nucleotide polymorphisms clearly differentiated japonica and indica rice; however, they were not associated with PH selection. Other new functional nucleotide polymorphisms in the coding, but not promoter, regions were involved in PH selection during rice domestication. Our study increasesunderstanding of the rice SD1 gene and provides additional evidence of this gene’s selection during rice domestication.ConclusionsOur findings provide evidence thatSD1 gene from wild rice enhances plant height and new functional nucleotide polymorphisms of this gene were artificially selected during cultivated rice differentiation.

Diverse panicle architecture results from various combinations of Prl5/GA20ox4 and Pbl6/APO1 alleles

Panicle architecture directly affects crop productivity and is a key target of high-yield rice breeding. Panicle length strongly affects panicle architecture, but the underlying regulatory mechanisms are largely unknown. Here, we show that two quantitative trait loci (QTLs), PANICLE RACHIS LENGTH5 (Prl5) and PRIMARY BRANCH LENGTH6 (Pbl6), independently regulate panicle length in rice. Prl5 encodes a gibberellin biosynthesis enzyme, OsGA20ox4. The expression of Prl5 was higher in young panicles resulting in panicle rachis elongation. Pbl6 is identical to ABERRANT PANICLE ORGANIZATION 1 (APO1), encoding an F-box-containing protein. We found a novel function that higher expression of Pbl6 is responsible for primary branch elongation. RNA-seq analysis revealed that these two genes independently regulate panicle length at the level of gene expression. QTL pyramiding of both genes increased panicle length and productivity. By combining these two genes in various combinations, we designed numerous panicle architecture without trade-off relationship.

CPPU may induce gibberellin-independent parthenocarpy associated with PbRR9 in \u2018Dangshansu\u2019 pear

Parthenocarpy is a valuable trait in self-incompatible plants, such as pear. N-(2-chloro-4-pyridyl)-N’-phenylurea (CPPU), a synthetic cytokinin analog, can induce parthenocarpy in pear (Pyrus spp.), but the mechanism of induction is unclear. To investigate the role of gibberellin in CPPU-induced parthenocarpy in pear, CPPU supplemented with paclobutrazol (PAC) was sprayed onto ‘Dangshansu’ pear. We found that the fruit set rate of pear treated with CPPU supplemented with PAC was identical to that in a CPPU-alone treatment group. In regard to cell development, CPPU mainly promoted hypanthium cell division and expansion, and PAC application had no influence on CPPU-induced cell development. RNA sequencing revealed that gibberellin 20 oxidase and gibberellin 3 oxidase genes were not differentially expressed following CPPU treatment. According to the analysis of fruit phytohormone content, the CPPU treatments did not induce gibberellin biosynthesis. These results suggest that CPPU-induced parthenocarpy may be gibberellin independent in ‘Dangshansu’ pear. After CPPU treatment, the indole acetic acid (IAA) content in fruit was significantly increased, and the abscisic acid (ABA) content was significantly decreased. Similarly, RNA sequencing revealed that many genes involved in the auxin and ABA pathways were significantly differentially expressed in the CPPU treatment groups; among them, indole-3-pyruvate monooxygenase (YUCCA) was significantly upregulated and 9-cis-epoxycarotenoid dioxygenase (NCED) was significantly downregulated. IAA and ABA may thus play important roles in CPPU-induced parthenocarpy. PbTwo-component response regulator9 (PbRR9), PbYUCCA4, and PbNCED6 were then selected to further elucidate the mechanism of CPPU-induced parthenocarpy. A yeast one-hybrid assay indicated that PbRR9 can combine with the PbYUCCA4 and PbNCED6 promoters. Dual luciferase assays revealed that PbRR9 can promote and repress the activities of the PbYUCCA4 and PbNCED6 promoters, respectively. After the transient expression of PbRR9 in fruits, PbYUCCA4 expression was significantly upregulated, and PbNCED6 expression was significantly downregulated. This study uncovered a CPPU-induced parthenocarpy mechanism that is different from that in tomato. CPPU may upregulate PbYUCCA4 and downregulate PbNCED6 by upregulating PbRR9, thereby increasing IAA content and decreasing ABA content to ultimately induce parthenocarpy in ‘Dangshansu’ pear. However, because only a single time point was used and because ‘botanical’ and ‘accessory’ fruits have different structures, this conclusion is still preliminary.

Multiple Metabolic Innovations and Losses Are Associated with Major Transitions in Land Plant Evolution.

Investigating the evolution of plant biochemistry is challenging because few metabolites are preserved in fossils and because metabolic networks are difficult to experimentally characterize in diverse extant organisms. We report a comparative computational approach based on whole-genome metabolic pathway databases of eight species representative of major plant lineages, combined with homologous relationships among genes of 72 species from streptophyte algae to angiosperms. We use this genomic approach to identify metabolic gains and losses during land plant evolution. We extended our findings with additional analysis of 305 non-angiosperm plant transcriptomes. Our results revealed that genes encoding the complete biosynthetic pathway for brassinosteroid phytohormones and enzymes for brassinosteroid inactivation are present only in spermatophytes. Genes encoding only part of the biosynthesis pathway are present in ferns and lycophytes, indicating a stepwise evolutionary acquisition of this pathway. Nevertheless, brassinosteroids are ubiquitous in land plants, suggesting that brassinosteroid biosynthetic pathways differ between earlier- and later-diverging lineages. Conversely, genes for gibberellin biosynthesis and inactivation using methyltransferases are found in all land plant lineages. This suggests that bioactive gibberellins might be present in bryophytes, although they have yet to be detected experimentally. We also found that cytochrome P450 oxidases involved in cutin and suberin production are absent in genomes of non-angiosperm plants that nevertheless do contain these biopolymers. Overall, we identified significant differences in crucial metabolic processes between angiosperms and earlier-diverging land plants and resolve details of the evolutionary history of several phytohormone and structural polymer biosynthetic pathways in land plants.

Manipulating Gibberellin Control Over Growth and Fertility as a Possible Target for Managing Wild Radish Weed Populations in Cropping Systems.

Wild radish is a major weed of Australian cereal crops. A rapid establishment, fast growth, and abundant seed production are fundamental to its success as an invasive species. Wild radish has developed resistance to a number of commonly used herbicides increasing the problem. New innovative approaches are needed to control wild radish populations. Here we explore the possibility of pursuing gibberellin (GA) biosynthesis as a novel molecular target for controlling wild radish, and in doing so contribute new insights into GA biology. By characterizing ga 3-oxidase (ga3ox) mutants in Arabidopsis, a close taxonomic relative to wild radish, we showed that even mild GA deficiencies cause considerable reductions in growth and fecundity. This includes an explicit requirement for GA biosynthesis in successful female fertility. Similar defects were reproducible in wild radish via chemical inhibition of GA biosynthesis, confirming GA action as a possible new target for controlling wild radish populations. Two possible targeting approaches are considered; the first would involve developing a species-specific inhibitor that selectively inhibits GA production in wild radish over cereal crops. The second, involves making crop species insensitive to GA repression, allowing the use of existing broad spectrum GA inhibitors to control wild radish populations. Toward the first concept, we cloned and characterized two wild radish GA3OX genes, identifying protein differences that appear sufficient for selective inhibition of dicot over monocot GA3OX activity. We developed a novel yeast-based approach to assay GA3OX activity as part of the molecular characterization, which could be useful for future screening of inhibitory compounds. For the second approach, we demonstrated that a subset of GA associated sln1/Rht-1 overgrowth mutants, recently generated in cereals, are insensitive to GA reductions brought on by the general GA biosynthesis inhibitor, paclobutrazol. The location of these mutations within sln1/Rht-1, offers additional insight into the functional domains of these important GA signaling proteins. Our early assessment suggests that targeting the GA pathway could be a viable inclusion into wild radish management programs that warrants further investigation. In drawing this conclusion, we provided new insights into GA regulated reproductive development and molecular characteristics of GA metabolic and signaling proteins.

Mutagenesis of a Quintuple Mutant Impaired in Environmental Responses Reveals Roles for CHROMATIN REMODELING4 in the Arabidopsis Floral Transition.

Several pathways conferring environmental flowering responses in Arabidopsis (Arabidopsis thaliana) converge on developmental processes that mediate the floral transition in the shoot apical meristem. Many characterized mutations disrupt these environmental responses, but downstream developmental processes have been more refractory to mutagenesis. Here, we constructed a quintuple mutant impaired in several environmental pathways and showed that it possesses severely reduced flowering responses to changes in photoperiod and ambient temperature. RNA-sequencing (RNA-seq) analysis of the quintuple mutant showed that the expression of genes encoding gibberellin biosynthesis enzymes and transcription factors involved in the age pathway correlates with flowering. Mutagenesis of the quintuple mutant generated two late-flowering mutants, quintuple ems1 (qem1) and qem2 The mutated genes were identified by isogenic mapping and transgenic complementation. The qem1 mutant is an allele of the gibberellin 20-oxidase gene ga20ox2, confirming the importance of gibberellin for flowering in the absence of environmental responses. By contrast, qem2 is impaired in CHROMATIN REMODELING4 (CHR4), which has not been genetically implicated in floral induction. Using co-immunoprecipitation, RNA-seq, and chromatin immunoprecipitation sequencing, we show that CHR4 interacts with transcription factors involved in floral meristem identity and affects the expression of key floral regulators. Therefore, CHR4 mediates the response to endogenous flowering pathways in the inflorescence meristem to promote floral identity.

Targeted mutation of GA20ox-2 gene using CRISPR/Cas9 system generated semi-dwarf phenotype in rice

Recently, the engineered CRISPR/Cas9 system has been applied to rapidly and efficiently modify the targeted gene(s) in a wide variety of plants. Recent studies of successful targeted mutagenesis using the CRISPR/Cas9 system with a single gRNA expression in rice plants have been reported. GA20ox-2 is a gene encoding an oxidase enzyme involved in the biosynthesis of gibberellin and linked to sd1 locus. A previous study revealed that mutation of this gene resulted in shorter stature of rice plant due to defects in the gibberellin’s signalling pathway. Here, we studied targeted mutation of OsGA20ox-2 gene in rice using the CRISPR/Cas9 system with the expression of two gRNAs. In this study, we introduced a single plasmid vector of CRISPR/Cas9 system harboring dual gRNAs to modify OsGA20ox-2 gene in a rice model cv. Kitaake via Agrobacterium-mediated transformation. Targeted mutagenesis of OsGA20ox-2 gene using CRISPR/Cas9 generated nine mutated rice lines with a mutation frequency of 90%. Most mutated lines (50%) had mutations in both OsGA20ox-2 gRNA. They resulted in homo-diallelic mutation type with 44 bp deletion, while three lines were heterozygous, one line was homo-diallelic with 2 bp insertion, and one line had no mutation. The K15 mutated rice line was identified as a homozygous two-nucleotide insertion and had the semi-dwarf phenotype, demonstrating that OsGA20ox-2 gene had been disrupted.

Research progress in biosynthesis and metabolism regulation of gibberellins in Gibberella fujikuroi

Gibberellin is one of the most important plant growth regulators, and widely used in agricultural production. However, the high cost of gibberellins production is restricting its efficient application. In recent years, biotechnological innovations have improved the synthesis of gibberellin. Gibberellin biosynthesis requires various enzymes. Current research focuses on the biosynthetic mechanisms of gibberellin and the metabolic engineering techniques to improve the production of gibberellin. This paper reviews the current research on gibberellin biosynthesis pathway, the key and enzymes environmental factors involved, and the metabolic regulation of gibberellin in Gibberella fujikuroi, summarizes the application of metabolic regulation in gibberellin biosynthesis, to provide the basis for achieving stable gibberellins production.

Effect of polar auxin transport and gibberellins on xylem formation in pine cuttings under adventitious rooting conditions

Maturation-related decline of adventitious root formation is one of the major factors affecting adventitious rooting in forest tree species. We demonstrate that inhibition of polar auxin transport promoted cambium and xylem differentiation in rooting-competent hypocotyl cuttings from Pinus radiata under conditions of adventitious root formation. Treatments with bioactive gibberellins inhibited rooting while at the same time inducing both the differentiation of a continuous ring of cambium and xylem formation. Treatments with inhibitors of gibberellin biosynthesis did not affect the rooting response. The results demonstrate that xylem parenchyma and procambial cells at the xylem poles of rooting-competent hypocotyl cuttings after excision and under conditions of adventitious root induction become adventitious root meristems or xylem, depending on the directional auxin flow. Gibberellin may interact with this pathway, inducing xylem differentiation and inhibiting rooting. We conclude that modifications of auxin flow at the rooting sites, and the priming of cambial cells to differentiate into xylem during tree ageing, may be associated with the maturation-related decline of adventitious root formation.

Comparative Transcriptome Analysis Identified Differentially Expressed Genes between Male and Female Flowers of Zanthoxylum armatum var. novemfolius

As a traditional spicy condiment, Zanthoxylum armatum var. novemfolius is of high economical and medicinal value. Despite the long history of human cultivation, the molecular mechanisms underlying flower development are still poorly understood in Z. armatum. In this study, we performed de novo transcriptome assembly and comparative analysis of female and male flowers in Z. armatum. A total of 94,771 unigenes were obtained, and 50,605 unigenes were successfully annotated against the public database. Transcriptome data showed that 20,431 annotated unigenes were differentially expressed genes. KEGG enrichment analysis revealed that the most representative pathway was plant hormone signal transduction. Among them, 41, 16, 41, 27, 95, and 40 unigenes were involved in the biosynthesis and signaling of abscisic acid, ethylene, cytokinin, gibberellin, auxin, and jasmonic acid, respectively. Transcription factors also played crucial roles in flower development, such as AGL11, PMADS2, and NAC. These results provided an important basis for characterizing the potential mechanism of flower development and enriching the knowledge of reproduction genetics in Z. armatum.

Transcriptome Profiling Analysis Reveals Co-regulation of Hormone Pathways in Foxtail Millet during Sclerospora graminicola Infection.

Sclerospora graminicola (Sacc.) Schroeter is a biotrophic pathogen of foxtail millet (Setaria italica) and increasingly impacts crop production. We explored the main factors for symptoms such as dwarfing of diseased plants and the “hedgehog panicle” by determining panicle characteristics of varieties infected with S. graminicola and analyzing the endogenous hormone-related genes in leaves of Jingu 21. Results indicated that different varieties infected by S. graminicola exhibited various symptoms. Transcriptome analysis revealed that the ent-copalyl diphosphate synthetase (CPS) encoded by Seita.2G144900 and ent-kaurene synthase (KS) encoded by Seita.2G144400 were up-regulated 4.7-fold and 2.8-fold, respectively. Results showed that the biosynthesis of gibberellin might be increased, but the gibberellin signal transduction pathway might be blocked. The abscisic acid (ABA) 8′-hydroxylase encoded by Seita.6G181300 was continuously up-regulated by 4.2-fold, 2.7-fold, 14.3-fold, and 12.9-fold from TG1 to TG4 stage, respectively. Seita.2G144900 and Seita.2G144400 increased 79-fold and 51-fold, respectively, at the panicle development stage, promoting the formation of a “hedgehog panicle”. Jasmonic acid-related synthesis enzymes LOX2s, AOS, and AOC were up-regulated at the early stage of infection, indicating that jasmonic acid played an essential role in early response to S. graminicola infection. The expression of YUC-related genes of the auxin synthesis was lower than that of the control at TG3 and TG4 stages, but the amidase encoded by Seita.2G313400 was up-regulated by more than 30-fold, indicating that the main biosynthesis pathway of auxin had changed. The results suggest that there was co-regulation of the hormone pathways during the infection of foxtail millet by S. graminicola.

Introducing selective agrochemical manipulation of gibberellin metabolism into a cereal crop

Use of growth retardants enables post-planting optimization of vegetative growth, which is particularly important given ongoing climate change. Mepiquat chloride is an economical and safe retardant widely applied in cotton farming, but it is not uniformly effective. Here, identification of its molecular target as the ent-copalyl diphosphate synthase that initiates gibberellin biosynthesis enabled the introduction of selective agrochemical inhibition, leaving intact more specialized metabolism important for resistance to biotic and abiotic stresses.

Effects of Gibberellin and Abscisic Acid on Asexual Reproduction from Graptopetalum paraguayense Leaves

Graptopetalum paraguayense E. Walther is an edible succulent plant that is native to Mexico. When leaves of G. paraguayense are detached from the mother plant, shoots and roots regenerate from the leaf base. To investigate the endogenous hormonal regulation of plant regeneration in G. paraguayense, we evaluated the effects of applying gibberellin (GA), abscisic acid (ABA), and phytohormone biosynthesis inhibitors to leaves detached from the mother plant. GA3 and paclobutrazol did not affect plant regeneration of G. paraguayense, whereas ABA treatment significantly suppressed plant regeneration. When leaves were treated with the ABA biosynthesis inhibitor fluridone at 10 μM, the frequency of shoot regeneration was more than twice that of the control on the 6th day after leaf detachment. In addition, when both fluridone and ABA were applied at the same time, the frequency of plant regeneration decreased to control levels or below. Endogenous ABA in leaves was approximately 1.3 ng gFW−1 just after leaf detachment, decreased to 0.3 ng gFW−1 by the 1st day after leaf detachment, and increased to 3.0 ng gFW−1 by the 9th day after leaf detachment. These findings indicate that ABA plays an important role in suppression of plant regeneration in G. paraguayense. Although plant regeneration during storage and transportation currently reduces the economic value of G. paraguayense, our findings may provide a method to delay unwanted plant formation at the leaf base.

Metconazole on Inhibition of Gibberellin Biosynthesis and Flowering Management in Mango

Gibberellins have been shown to suppress floral development in mango, thus farmers have used growth retardants, especially paclobutrazol, to inhibit gibberellin biosynthesis, but in many countries such as Brazil, this is the unique registered molecule, which affects sustainability of the mango industry. The objective of this study was to evaluate the effect of metconazole on gibberellin biosynthesis inhibition and carbohydrate accumulation in ‘Palmer’ mango grown in semi-arid conditions. The experiment was accomplished from 2015 to 2017 in an experimental orchard located in Petrolina, Pernambuco, Brazil. The experimental design were randomized blocks with five treatments, five replications and three plants per replication. The treatments consisted of metconazole (0, 0.7, 1.0 or 1.3 g) and paclobutrazol (1.0 g) application per linear meter of plant canopy. According to the results, metconazole efficiently inhibits gibberellin biosynthesis in mango, but it affects AG1 + AG3 (Gibberellic Acid) and AG4 differently. Therefore, metconazole can potentially be used on mango flowering management, but further studies are required to determine specific management practices.

Comparative transcriptomics of stem bark reveals genes associated with bast fiber development in Boehmeria nivea L. gaud (ramie)

BackgroundBoehmeria nivea L. Gaud (Ramie) produces one of the longest natural fibers in nature. The bark of ramie mainly comprises of the phloem tissue of stem and is the raw material for fiber. Therefore, identifying the molecular regulation of phloem development is important for understanding of bast fiber biosynthesis and improvement of fiber quality in ramie.ResultsIn this study, we collected top bud (TB), bark from internode elongating region (ER) and bark from internode fully elongated region (FER) from the ramie variety Zhongzhu No. 1. Histological study indicated that these samples contain phloem tissues at different developmental and maturation stages, with a higher degree of maturation of phloem tissue in FER. RNA sequencing (RNA-seq) was performed and de novo transcriptome was assembled. Unigenes and differentially expressed genes (DEGs) in these three samples were identified. The analysis of DEGs by using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed clear differences in gene expression between ER and FER. Some unigenes involved in secondary cell wall biosynthesis were up-regulated in both ER and FER, while unigenes for some cell wall components or cell wall modifications showed differential expression between ER and FER. In addition, the ethylene respond factors (ERFs) in the ethylene signaling pathway were up-regulated in FER, and ent-kaurenoic acid oxidase (KAO) and GA 20-oxidase (GA20ox) for gibberellins biosynthesis were up-regulated while GA 2-oxidase (GA2ox) for gibberellin inactivation was down-regulated in FER.ConclusionsBoth morphological study and gene expression analysis supported a burst of phloem and vascular developmental processes during the fiber maturation in the ramie stem, and ethylene and gibberellin are likely to be involved in this process. Our findings provide novel insights into the phloem development and fiber maturation in ramie, which could be useful for fiber improvement in ramie and other fiber crops.

Shading of the mother plant during seed development promotes subsequent seed germination in soybean.

The effect of shading during seed development on subsequent germination remains largely unknown. In this study, two soybean (Glycine max) seed production systems, monocropping (MC) and maize-soybean intercropping (IC), were employed to examine the effects of shading of the mother plant on subsequent seed germination. Compared to the MC soybean seeds, which received light, the developing IC seeds were exposed to shade resulting from the taller neighboring maize plants. The IC seeds germinated faster than the MC seeds, although there was no significant difference in the thickness of the seed coat. The concentration of soluble pro-anthocyanidin in the IC seed coat was significantly lower than that in the MC seed coat. Changes in the concentrations of several types of fatty acids in IC seeds were also observed, the nature of which were consistent with the effect on germination. The expression levels of genes involved in abscisic acid (ABA) biosynthesis were down-regulated in IC seeds, while the transcription levels of the genes related to gibberellin (GA) biosynthesis were up-regulated. This was consistently reflected in decreased ABA concentrations and increased active GA4 concentrations in IC seeds, resulting in an increased GA4/ABA ratio. Our results thus indicated that shading of the mother plant during seed development in soybean promoted subsequent germination by mediating the biosynthesis of pro-anthocyanidins, fatty acids, and phytohormones.

Molecular Mechanism of Vegetative Growth Advantage in Allotriploid Populus.

Allotriploid poplar has a prominent vegetative growth advantage that impacts dramatically on lumber yield. The growth regulation is complex which involves abundant genes, metabolic and signaling pathways, while the information about the functional control process is very little. We used high-throughput sequencing and physiological index measurement to obtain a global overview of differences between allotriploid and diploid Populus. The genes related to plant growth advantage show a higher expression compared to diploid, and most of them are revolved around hormones, photosynthesis and product accumulation. Thus, allotriploid Populus showed more efficient photosynthesis, carbon fixation, sucrose and starch synthesis, and metabolism as well as augmented biosynthesis of auxin, cytokinin, and gibberellin. These data enable the connection of metabolic processes, signaling pathways, and specific gene activity, which will underpin the development of network models to elucidate the process of triploid Populus advantage growth.

DNA methylation is involved in the regulation of pepper fruit ripening and interacts with phytohormones.

There is growing evidence to suggest that epigenetic tags, especially DNA methylation, are critical regulators of fruit ripening. To examine whether this is the case in sweet pepper (Capsicum annuum) we conducted experiments at the transcriptional, epigenetic, and physiological levels. McrBC PCR, bisulfite sequencing, and real-time PCR demonstrated that DNA hypomethylation occurred in the upstream region of the transcription start site of some genes related to pepper ripening at the turning stage, which may be attributed to up-regulation of CaDML2-like and down-regulation of CaMET1-like1, CaMET1-like2, CaCMT2-like, and CaCMT4-like. Silencing of CaMET1-like1 by virus-induced gene silencing led to DNA hypomethylation, increased content of soluble solids, and accumulation of carotenoids in the fruit, which was accompanied by changes in expression of genes involved in capsanthin/capsorubin biosynthesis, cell wall degradation, and phytohormone metabolism and signaling. Endogenous ABA increased during fruit ripening, whereas endogenous IAA showed an opposite trend. No ethylene signal was detected during ripening. DNA hypomethylation repressed the expression of auxin and gibberellin biosynthesis genes as well as cytokinin degradation genes, but induced the expression of ABA biosynthesis genes. In mature-green pericarp, exogenous ABA induced expression of CaDML2-like but repressed that of CaCMT4-like. IAA treatment promoted the transcription of CaMET1-like1 and CaCMT3-like. Ethephon significantly up-regulated the expression of CaDML2-like. Treatment with GA3 and 6-BA showed indistinct effects on DNA methylation at the transcriptional level. On the basis of the results, a model is proposed that suggests a high likelihood of a role for DNA methylation in the regulation of ripening in the non-climacteric pepper fruit.

Effect of soil applied paclobutrazol on flowering, fruit set and fruit yield of litchi (Litchi chinensis Sonn.) cv. rose scented

The litchi (Litchi chinensis Sonn.) is the most renowned subtropical evergreen fruit, famous for its deliciously flavored, excellent quality and attractive red colour. Paclobutrazol (PBZ) is a cell elongation and internode extension inhibitor that retards plant growth by inhibition of gibberellins biosynthesis. the effect of paclobutrazol at varying time intervals of litchi as soil drench application (1.00-4.00 g a.i. per meter canopy diameter) on flowering, fruiting and yield of litchi was investigated during 2016-18 in Pantnagar condition. Application of paclobutrazol at the rate 2.0, 3.0 and 4.0 a.i./tree through soil application method was noted to be more efficient in reducing panicle length, panicle width and advanced the date of panicle emergence. Soil applied paclobutrazol @ 2.0, 3.0 a.i./tree increased the duration of flowering, total number of flowers, male flowers, female flowers, fruit set and fruit yield. the minimum panicle length (20.45 cm) was found in P2 (40 ml/tree) followed by P3 (20.54 cm) and P4 (20.98 cm). However, the maximum panicle length was recorded under control (25.17 cm). the effect of different time intervals showed the lowest panicle length (21.92 cm) in D3 (November). the maximum fruit yield (56.79 kg/ tree) was found in P3 (60 ml/tree) followed by P2 (56.68 kg/tree), while the minimum was recorded under control (44.98 kg/tree).