Expression Of Flowering Genes Research Articles

Cytokinin accumulation and flowering gene expression are orchestrated for floral meristem development in longan (Dimocarpus longan Lour.) after chemical flower induction

Under non-inductive environmental conditions longan trees (Dimocarpus longan Lour.) were subjected to potassium chlorate (KClO3) applications, solely or in combination with shoot girdling or defoliation treatments, to induce flowering. Treated trees showed visible flower buds four weeks after treatment, while untreated reference trees remained vegetative. Trees treated with KClO3 solely and in combination with apical shoot defoliation flowered terminally at the shoot apex. KClO3 treatment in combination with girdling caused flowering exclusively at the lateral buds immediately below the girdle. Results from histological and hormone analyses are integrated with longan flowering gene expression data to build a comprehensive time course model for chemical flower induction in longan. The increased cytokinin concentration in shoot apex tissues, likely due to de novo biosynthesis and translocation, corresponds with transient up-regulation of the flower promoting gene Dimocarpus longan FLOWERING LOCUS 1 (DlFT1) in mature leaves after KClO3 treatment. Both occur during the presumed period of flower induction approximately at 10 days after treatment. Subsequently, and with some delay floral homeotic genes Dimocarpus longan APETALA 1 (DlAP1) are up-regulated in the buds indicating flower bud development, which coincides with visible floral meristems in histological specimen. The specific cytokinin accumulation and flowering gene expression pattern suggest a tight orchestration of hormonal and genetic pathways in chemically induced longan.

Flowering in Persian walnut: patterns of gene expression during flower development

BackgroundFlower development and sufficient fruit set are important parameters with respect to walnut yield. Knowledge about flowering genes of fruit trees can help to conduct better molecular breeding programs. Therefore, this study was carried out to investigate the expression pattern of some flowering genes (FT, SOC1, CAL, LFY and TFL1) in Persian walnut (cv. Chandler) during the growing season and winter dormancy.ResultsThe results showed that walnut flower induction and initiation in Shahmirzad, Iran occurred in early June and late September, respectively. After meeting chilling and heat requirement, flower differentiation and anthesis occurred in late-March and mid-April to early-May, respectively. Study of flowering gene expression showed that the expression of the FT gene increased in three stages including before breaking of bud dormancy, from late March to late April (coincided with flower differentiation and anthesis) and from late May to mid-June (coincided with flower induction). Like FT, the expression of SOC1 gene increased during flower induction and initiation (mid-May to early-August) as well as flower anthesis (mid-April to early-May). LFY and CAL genes as floral meristem identity genes are activated by FT and SOC1 genes. In contrast with flowering stimulus genes, TFL1 showed overexpression during winter dormancy which prevented flowering.ConclusionThe expression of FT gene activated downstream floral meristem identity genes including SOC1, CAL and LFY which consequently led to release bud dormancy as well as flower anthesis and induction. Also, TFL1 as a flowering inhibitor gene in walnut showed overexpression during the bud dormancy. Chilling accumulation reduced TFL1 gene expression and increased the expression of flowering genes which ultimately led to overcome dormancy.

Flowering gene expression in Indonesian long harvest black rice (Oryza sativa L. ‘Cempo Ireng’)

Many studies have reported the great potency of black rice as functional food for human diet. Cempo Ireng is one of Indonesian black rice cultivars with the highest content of anthocyanin. However, it also suffers from long harvest period. This experiment aims at investigating the behavior of the flowering genes in order to gain basic information to develop this cultivar. We sampled the leaves’ blades of Black Rice ‘Cempo Ireng’ at 48, 55, 68, 81, and 90 DAP then performed RNA isolation and cDNA synthesis, amplification of targeted flowering genes, and a semi-quantitative analysis to see the expression of flowering genes. Our results showed that the flowering genes Hd3a and RFT1 were redundantly up-regulated to induce flowering in black rice Cempo Ireng under a neutral day condition in a tropical region. We also noted that the patterns of FT-like genes and flowering regulatory genes including FT-L5, FT-L6, FT-L9, FT-L10 and Hd1, OsCOL4 were expressed together with two major flowering genes. FT-like genes were temporally co-expressed with two flowering genes Hd3a and RFT1, whereas the Hd1 had a unique expression pattern. Meanwhile, OsCOL4 as the flowering repressor was only detected in the early stage when the flowering gene Hd3a began to express. The results suggest that black rice Cempo Ireng has similar and conserved flowering pathway under a neutral day condition as indicated in the common rice flowering models.

Early and late flowering gene expression patterns in maize

A recommendation of: Maud Irène Tenaillon, Khawla Sedikki, Maeva Mollion, Martine Le Guilloux, Elodie Marchadier, Adrienne Ressayre, Christine Dillmann Transcriptomic response to divergent selection for flowering time in maize reveals convergence and key players of the underlying gene regulatory network https://doi.org/10.1101/461947

Interrelations of growth regulators, carbohydrates and expression of flowering genes (FT, LFY, AP1) in leaf and shoot apex of regular and alternate bearing mango (Mangifera indica L.) cultivars during flowering

Two mango cultivars, Amrapali (regular bearer) and Dashehari (alternate bearer), contrasting for bearing habit was assessed for endogenous phytohormone, carbohydrates and expression of floral inductive genes during flowering. Cultivar Amrapali had higher concentration of growth regulators like ABA, auxin, zeatin, salicylic acid and jasmonic acid and carbohydrates, whereas lower GA content compared to cv. Dashehari and the content increased during flowering when compared to vegetative stage. Gibberellic acid levels was higher in all the stages of bud growth in alternate bearer cv. Dashehari compared to the regular bearer cv. Amrapali. However, the starch content was higher in cv. Amrapali compared to cv. Dashehari. Studies on flower inducing genes indicated that the expression of MiLFY gene was found to be higher in the flowering panicles. Expression of MiFT gene was higher in regular bearer cv. Amrapali compared to the alternate bearer cv. Dashehari and the expression was observed only in leaves which are adjacent to the apical buds during flowering. Higher expression of MiAP1 gene was also observed in the leaves during the floral induction phase. MiFT and MiAP1 genes found to have a negative relation with gibberellic acid and its derivatives. The results indicate that positive regulators of flowering were higher in regular bearing cultivar Amrapali compared to alternate bearing cultivar Dashehari.

Gene Expression Analysis Using Clustering Techniques and Evaluation Indices

Data Mining refers to as the nontrivial process of deriving and identifying valid, novel, potentially useful and ultimately understandable pattern in data. Data mining can be classified into various models such as Clustering, Decision trees, Association rules, and Sequential pattern and time series. In this work, more emphasis is given on clustering technique to analyses Genetic Expression data under Bioinformatics approach. Innovative technologies like DNA Microarray methodology in experimental molecular biology, has produced huge amounts of valuable data in the profile of gene expression. It is now possible to simultaneously monitor the expression levels of thousands of genes during important biological processes and across collections of related samples. Constant upsurge of experimental data has produced new challenges in terms of maintenance, storage and analysis to derive meaningful patterns. Many clustering algorithms have been proposed for analysis of the gene expression data. However, the evaluation of feasible and applicable clustering algorithms is becoming an important issue in current bioinformatics research. In this article, four clustering algorithms (K-Means, Hierarchical Clustering, Self-Organizing map (SOM) and DBSCAN) have been studied on Iris flower gene expression datasets. The clustering efficiency of each algorithm is accessed by various external and internal clustering evaluation indices. The results generated from this work were further analyzed by plotting graphs and charts across different algorithms, different indices and datasets to analyze the similarity of clusters generated by different algorithms and thereby enable comparisons of different clustering methods.

Differential expression of flowering genes in Arabidopsis thaliana under chronic and acute ionizing radiation

Purpose: Chronic and acute irradiations have drastic effects on flowering stage that plays an important role in further seed development and can determine seed yield. The expression of the key flowering genes, AP1, CO, GI, FT, FLC, and LFY, sensitive to irradiation repair gene RAD51 and the proliferation gene PCNA2 were studied in the wild-type Arabidopsis thaliana (Columbia ecotype) under chronic and acute irradiations.Materials and methods: Chronic irradiation was performed using the radioactive isotope 137СsCl in two total doses of 3 cGy and 17 cGy, with the dose rate of 10−7 cGy/s and 6.8 10−6 cGy/s, respectively. The plants were grown under chronic irradiation during 6 weeks, from seeds till the 6.3 stage of flowering. For acute exposure, the plants were X-ray irradiated one time at the 5.0 development stage (20 days old) by a total dose of 15 Gy with the dose rate of 89 cGy/s.Results: After chronic irradiation with the 3 cGy dose the irradiated plants demonstrated 8 ± 2.8 days earlier flowering than in the control group. However, at the 17 cGy chronic and at the 15 Gy acute doses plants showed 14 ± 3.7 and 2 ± 1.4 days later flowering, respectively. The 3 cGy chronic exposure significantly increased the expression of the CO gene by a factor of 1.152 (1.087–1.217 95% C.I.) and decreased the expression of the FT gene by a factor of 0.128 (0.021–0.396 95% C.I.). The 17 cGy chronic exposure decreased expression of the AP1 gene by a factor of 0.872 (0.803–0.940 95% C.I.) and the LFY gene by a factor of 0.471 (0.306–0.687 95% C.I.). The 15 Gy acute exposure decreased the expression of the AP1 gene by a factor of 0.104 (0.074–0.144 95% C.I.) and the PCNA2 gene by a factor of 0.346 (0.238–0.488 95% C.I.).Conclusions: The increased expression of the CO gene and decreased expression of the AP1 and FT genes under the lower dose of chronic exposure were associated with earlier flowering. The acute exposure increased the expression of the PCNA2 gene and decreased the expression of the flowering genes, except AP1. The flowering was delayed under both the higher dose of chronic exposure and under acute exposure, but it was less affected by the latter. Presumably, it was related to the activation of DNA repair under the 3 cGy chronic and 15 Gy acute irradiations.

Overexpression of CCCH zinc finger protein gene delays flowering time and enhances salt tolerance in Arabidopsis by increasing fatty acid unsaturation

CCCH-type zinc-finger proteins constitute a large family playing key roles during plant development and growth. In the present study, we investigated the involvement of the CCCH-type zinc finger protein of AtZFP1 (At2g25900) in flowering and salt stress response in Arabidopsis. Compared with the wild type (WT), bolting and flowering were delayed in AtZFP1-overexpressing plants. Real-time PCR analysis of floral regulating genes in overexpressing Arabidopsis revealed that enhanced expression of FLC decreased the expressions of FT and SOC1. The Fv/Fm of overexpressing Arabidopsis lines was unchanged under salt stress. In contrast, ΦPSII activity and PSI oxidoreduction decreased in WT, overexpressing and mutant strains under salt stress conditions, with the smallest reduction in these parameters observed in the overexpressing strains. These results suggest that the CCCH zinc-finger protein AtZFP1 primarily controls flowering time by changing the expression of flowering genes under long-day conditions. The overexpression of this protein delayed flowering and increased the content and double-bond index of unsaturated fatty acids. Elevation of unsaturated fatty acid content might play important role in protecting the photosynthetic apparatus and maintaining the membrane function at salt stress by alleviating PSII and PSI photoinhibition.

Identification and characterization of NF-Y gene family in walnut (Juglans regia L.)

BackgroundThe eukaryotic transcription factor NF-Y (which consists of NF-YA, NF-YB and NF-YC subunits) is involved in many important plant development processes. There are many reports about the NF-Y family in Arabidopsis and other plant species. However, there are no reports about the NF-Y family in walnut (Juglans regia L.).ResultsThirty-three walnut NF-Y genes (JrNF-Ys) were identified and mapped on the walnut genome. The JrNF-Y gene family consisted of 17 NF-YA genes, 9 NF-YB genes, and 7 NF-YC genes. The structural features of the JrNF-Y genes were investigated by comparing their evolutionary relationship and motif distributions. The comparisons indicated the NF-Y gene structure was both conserved and altered during evolution. Functional prediction and protein interaction analysis were performed by comparing the JrNF-Y protein structure with that in Arabidopsis. Two differentially expressed JrNF-Y genes were identified. Their expression was compared with that of three JrCOs and two JrFTs using quantitative real-time PCR (qPCR). The results revealed that the expression of JrCO2 was positively correlated with the expression of JrNF-YA11 and JrNF-YA12. In contrast, JrNF-CO1 and JrNF-YA12 were negatively correlated.ConclusionsThirty-three JrNF-Ys were identified and their evolutionary, structure, biological function and expression pattern were analyzed. Two of the JrNF-Ys were screened out, their expression was differentially expressed in different development periods of female flower buds, and in different tissues (female flower buds and leaf buds). Based on prediction and experimental data, JrNF-Ys may be involved in flowering regulation by co-regulate the expression of flowering genes with other transcription factors (TFs). The results of this study may make contribution to the further investigation of JrNF-Y family.

Sex‐biased gene expression in flowers, but not leaves, reveals secondary sexual dimorphism in Populus balsamifera

Because sexual dimorphism in plants is often less morphologically conspicuous than in animals, studies of sex-biased gene expression may provide a quantitative metric to better address their commonality, molecular pathways, consistency across tissues and taxa, and evolution. The presence of sex-biased gene expression in tissues other than the androecium or gynoecium, termed secondary sexual characters, suggests that these traits arose after the initial evolution of dioecy. Patterns of sequence evolution may provide evidence of positive selection that drove sexual specialization. We compared gene expression in male and female flowers and leaves of Populus balsamifera to assess the extent of sex-biased expression, and tested whether sex-biased genes exhibit elevated rates of protein evolution. Sex-biased expression was pervasive in floral tissue, but nearly absent in leaf tissue. Female-biased genes in flowers were associated with photosynthesis, whereas male-biased genes were associated with mitochondrial function. Sex-biased genes did not exhibit elevated rates of protein evolution, contrary to results from other studies in animals and plants. Our results suggest that the ecological and physiological constraints associated with the energetics of flowering, rather than sexual conflict, have probably shaped the differences in male and female gene expression in P.balsamifera.

Association Mapping of Flowering and Height Traits in Germplasm Enhancement of Maize Doubled Haploid (GEM-DH) Lines.

Flowering and height related traits are extensively studied in maize for three main reasons: 1) easily obtained phenotypic measurements, 2) highly heritable, and 3) importance of these traits to adaptation and grain yield. However, variation in flowering and height traits is extensive and findings from previous studies are genotype specific. Herein, a diverse panel of exotic derived doubled haploid lines, in conjunction with genome-wide association analysis, is used to further explore adaptation related trait variation of exotic germplasm for potential use in adapting exotic germplasm to the U.S. Corn-Belt. Phenotypes for the association panel were obtained from six locations across the central-U.S. and genotyping was performed using the genotyping-by-sequencing method. Nineteen flowering time candidate genes were found for three flowering traits. Eighteen candidate genes were found for four height related traits, with the majority of the candidate genes relating to plant hormones auxin and gibberellin. A single gene was discovered for ear height that also had effects on -like flowering gene expression levels. Findings will be used to inform future research efforts of the USDA Germplasm Enhancement of Maize project and eventually aid in the rapid adaptation of exotic germplasm to temperate U.S. environments.

Molecular Genetic Dissection of Sugarcane Flowering under Equatorial Field Conditions

Sugarcane is a tropical crop used for sugar and biofuel production in tropical and equatorial regions of the globe. Sugarcane flowering is intrinsically induced in equatorial regions due to long-day conditions. Flower development is problematic for this crop because it halts vegetative growth, leading to a reduction of the sugar accumulated in the stalks, and significant yield loss. Notwithstanding, the identification of genes differentially expressed in contrasting cultivars can potentially reveal markers and tools to generate genotypes more suitable for expanding the geographical limits of this crop. Thus, dissecting the flowering gene expression network under field conditions is highly relevant for breeding. We report the analysis of subtractive cDNA libraries produced from shoot apical meristem of cultivars contrasting for flowering time growing in production fields under equatorial conditions. Transcripts with homology to POLYPHENOL OXIDASE (PPO), CALMODULIN (CAM), PHOSPHATIDYLCHOLINE/PHOSPHATIDYLINOSITOL-TRANSFER PROTEIN (SEC14), OBTUSIFOLIOL-14-Α-DEMETHYLASE (CYP51), 14–3-3, and the phosphotransferases SHAGGY KINASE (GSK), PROTEIN KINASE C INHIBITOR (PKCI), and SERINE/THREONINE PHOSPHATASE (PP1) were identified as differentially expressed in the subtractive libraries and further chosen for RT-qPCR validation and in silico interactome analyses. Our results suggest that ScPPO, ScSEC14 and Sc14–3-3 may act as flowering inhibitors. RT-qPCR data also revealed two 14–3-3 isoforms as potential flowering markers. Sc14–3-3 was structurally and phylogenetically characterized and its genomic architecture was analysed in two BAC clones, showing that they probably correspond to two different loci with confirmed synteny to other grass genomes. This work reveals potential novel mechanisms of flowering in grasses with implications to crop breeding.

HSP90 canonical content organizes a molecular scaffold mechanism to progress flowering.

Highly interactive signaling processes constitute a set of parameters intertwining in a continuum mode to shape body formation and development. A sophisticated gene network is required to integrate environmental and endogenous cues in order to modulate flowering. However, the molecular mechanisms that coordinate the circuitries of flowering genes remain unclear. Here using complemented experimental approaches, we uncover the decisive and essential role of HEAT SHOCK PROTEIN 90 (HSP90) in restraining developmental noise to an acceptable limit. Localized depletion of HSP90 mRNAs in the shoot apex resulted in low penetrance of vegetative-to-reproductive phase transition and completely abolished flower formation. Extreme variation in expression of flowering genes was also observed in HSP90 mRNA-depleted transformed plants. Transient heat-shock treatments moderately increased HSP90 mRNA levels and rescued flower arrest. The offspring had a low, nevertheless noticeable failure to promote transition from vegetative into the reproductive phase and showed flower morphological heterogeneity. In floral tissues a moderate variation in HSP90 transcript levels and in the expression of flowering genes was detected. Key flowering proteins comprised clientele of the molecular chaperone demonstrating that the HSP90 is essential during vegetative-to-reproductive phase transition and flower development. Our results uncover that HSP90 consolidates a molecular scaffold able to arrange and organize flowering gene network and protein circuitry, and effectively counterbalance the extent to which developmental noise perturbs phenotypic traits.

Differential Expression of Flowering Genes between Rapid- and Slow-Cycling Brassica rapa

Flowering time is a very important agronomic trait in Brassica crops and regulation of the time is one of major factor in the breeding program. To understand the control of flowering time in Brassica rapa, we have carried out Br300K microarray with two contrasting Brassica inbred lines, Rapid Cycling B. rapa (RCBr) as rapid cycling type and B. rapa ssp. pekinensis inbred line Chiifu as slow flowering phenotype. Reproductive process-related genes were specifically expressed in RCBr, whereas environmental stimuli-responsive genes in Chiifu. Flowering stimulating genes, such as BrFT and BrSOC1, were preferentially expressed in RCBr, while flowering repressing genes, such as BrFLC and BrMAF4, expressed in Chiifu. Several paralogues present in B. rapa, BrFLCs and BrCOLs, were expressed with paralog-specific pattern depending on flowering phenotypes: i.e., BrFLC1 and BrFLC2, major floral repressors, were expressed in Chiifu, BrFLCL/BrFLC5 in RCBr and BrFLC3 in both plants. The expression of several flowering repressing genes was gradually decreased in RCBr growth, but increased in Chiifu growth. However, the expression of genes involved in photoperiodic flowering was no difference between these two plants under LD and SD conditions, indicating photoperiodic pathway is not major factor to distinguish fast vs. slow flowering in B. rapa. The mechanism underlined in the rapid or fast flowering of RCBr would be further elucidated in association with the controlling mechanism of its short life span.

Regulation of DTA-6 by Abscission Cellulase and GmAC Gene Expression in Flowers and Pods of Soybean

It is effective to regulate abscission of soybean flowers and pods by spraying plant growth regulators (PGRs). This study was carried out to determine the effect of DTA-6 on abscission cellulase (AC) activity, abscission cellulase gene (GmAC) expressive, abscission of flowers and pods, and yield in soybean. DTA-6 was foliage sprayed at R1 stage on three varieties of Suinong 28, Kenfeng 16, and Hefeng 50 in 2012 and 2013. The results demonstrated that DTA-6 treatment inhibited GmAC gene expression in abscission zone of flower and pod, with the maximum reduction of 51% among three varieties compared with the control. The abscission cellulase activity was periodically decreased by DTA-6, with different decrements among soybean culti- vars. DTA-6 significantly decreased (P<0.05) abscission rate of soybean flowers and pods, and significantly increased yield (P<0.05). The relative expression of abscission cellulase gene (GmAC) in abscission zone of flowers-pods was decreased and the AC activity was regulated by DTA-6, resulting in reduced abscission rate of soybean flowers and pods and promoted yield.

Overexpression of soybean miR172c confers tolerance to water deficit and salt stress, but increases ABA sensitivity in transgenic Arabidopsis thaliana.

MiRNAs play crucial roles in many aspects of plant development and the response to the environment. The miR172 family has been shown to participate in the control of flowering time and the response to abiotic stress. This family regulates the expression of APETALA2 (AP2)-like transcription factors in Arabidopsis. In the present study, soybean (Glycine max L. Merr.) miR172c, a member of the miR172 family, and its target gene were investigated for abiotic stress responses in transgenic Arabidopsis. gma-miR172c was induced by abscisic acid (ABA) treatments and abiotic stresses, including salt and water deficit. 5'-RACE (5'-rapid amplification of cDNA ends) assays indicated that miR172c directed Glyma01g39520 mRNA cleavage in soybeans. Overexpression of gma-miR172c in Arabidopsis resulted in reduced leaf water loss and increased survival rate under stress conditions. Meanwhile, the root length, germination rate, and cotyledon greening of transgenic plants were improved during both high salt and water deficit conditions. In addition, transgenic plants exhibited hypersensitivity to ABA during both the seed germination and post-germination seedling growth stages. Stress-related physiological indicators and the expression of stress/ABA-responsive genes were affected by abiotic treatments. The overexpression of gma-miR172c in Arabidopsis promoted earlier flowering compared with the wild type through modulation of the expression of flowering genes, such as FT and LFY during long days, especially under drought conditions. Glyma01g39520 weakened ABA sensitivity and reduced the tolerance to drought stress in the snz mutant of Arabidopsis by reducing the expression of ABI3 and ABI5. Overall, the present results demonstrate that gma-miR172c confers water deficit and salt tolerance but increased ABA sensitivity by regulating Glyma01g39520, which also accelerates flowering under abiotic stresses.

The dynamics of FLOWERING LOCUS T expression encodes long-day information.

Long days repeatedly enhance the expression of the FLOWERING LOCUS T (FT) gene during the evening and early night. This signal induces flowering despite low FT expression the rest of the day. To investigate whether this temporal behaviour transmits information, plants of Arabidopsis thaliana were exposed to different day-night cycles, including combinations that induced FT expression out of normal hours. Flowering time best correlated with the integral of FT expression over several days, corrected for a higher evening and early night sensitivity to FT. We generated a system to induce FT expression in a leaf removed 8-12h later. The expression of flowering genes in the apex and flowering required cycles of induction repeated over several days. Evening and early night FT induction was the most effective. The temporal pattern of FT expression encodes information that discriminates long days from other inputs.

High-throughput transcriptome analysis of the leafy flower transition ofCatharanthus roseusinduced by peanut witches’ broom phytoplasma infection

Peanut witches’ broom (PnWB) phytoplasmas are obligate bacteria that cause leafy flower symptoms in Catharanthus roseus. The PnWB-mediated leafy flower transitions were studied to understand the mechanisms underlying the pathogenhost interaction. The whole transcriptome profiles from healthy flowers and stage 4 (S4) PnWB-infected leafy flowers of C. roseus were investigated using next-generation sequencing (NGS). More than 60,000 contigs were generated using a de novo assembly approach, and 34.2% of the contigs (20,711 genes) were annotated as putative genes through name-calling, open reading frame determination, and gene ontology analyses. Furthermore, a customized microarray based on this sequence information was designed and used to further analyze samples at various stages. In the NGS profile, 87.8% of the genes showed expression levels that were consistent with those in the microarray profiles, suggesting that accurate gene expression levels can be detected using NGS. The data revealed that defense-related and flowering gene expression levels were altered in S4 PnWB-infected leafy flowers, indicating that the immunity and reproductive stages of C. roseus were compromised. The network analysis suggested that the expression levels of more than 1,000 candidate genes were highly associated with CrSVP1/2 and CrFT gene expression, which might be crucial in the leafy flower transition. This study provides a new perspective for understanding the mechanisms underlying the leafy flowering transition caused by hostpathogen interactions through analyzing bioinformatics data obtained using a powerful, rapid high-throughput technique.

Arabidopsis MRG domain proteins bridge two histone modifications to elevate expression of flowering genes.

Trimethylation of lysine 36 of histone H3 (H3K36me3) is found to be associated with various transcription events. In Arabidopsis, the H3K36me3 level peaks in the first half of coding regions, which is in contrast to the 3′-end enrichment in animals. The MRG15 family proteins function as ‘reader’ proteins by binding to H3K36me3 to control alternative splicing or prevent spurious intragenic transcription in animals. Here, we demonstrate that two closely related Arabidopsis homologues (MRG1 and MRG2) are localised to the euchromatin and redundantly ensure the increased transcriptional levels of two flowering time genes with opposing functions, FLOWERING LOCUS C and FLOWERING LOCUS T (FT). MRG2 directly binds to the FT locus and elevates the expression in an H3K36me3-dependent manner. MRG1/2 binds to H3K36me3 with their chromodomain and interact with the histone H4-specific acetyltransferases (HAM1 and HAM2) to achieve a high expression level through active histone acetylation at the promoter and 5′ regions of target loci. Together, this study presents a mechanistic link between H3K36me3 and histone H4 acetylation. Our data also indicate that the biological functions of MRG1/2 have diversified from their animal homologues during evolution, yet they still maintain their conserved H3K36me3-binding molecular function.

Nitrogen as a key regulator of flowering in Fagus crenata: understanding the physiological mechanism of masting by gene expression analysis.

The role of resource availability in determining the incidence of masting has been widely studied, but how floral transition and initiation are regulated by the resource level is unclear. We tested the hypothesis that floral transition is stimulated by high resource availabiltiy in Fagus crenata based on a new technique, the expression analyses of flowering genes. We isolated F. crenata orthologues of FLOWERING LOCUS T, LEAFY and APETALA1, and confirmed their functions using transgenic Arabidopsis thaliana. We monitored the gene expression levels for 5 years and detected a cycle of on and off years, which was correlated with fluctuations of the shoot-nitrogen concentration. Nitrogen fertilisation resulted in the significantly higher expression of flowering genes than the control, where all of the fertilised trees flowered, whereas the control did not. Our findings identified nitrogen as a key regulator of mast flowering, thereby providing new empirical evidence to support the resource budget model.