Flowering Genes Research Articles

Flowering repressor CmSVP recruits the TOPLESS corepressor to control flowering in chrysanthemum.

Plant flowering time is induced by environmental and endogenous signals perceived by the plant. The MCM1-AGAMOUSDEFICIENS-Serum Response Factor-box (MADS-box) protein SHORT VEGETATIVE PHASE (SVP) is a pivotal repressor that negatively regulates the floral transition during the vegetative phase; however, the transcriptional regulatory mechanism remains poorly understood. Here, we report that CmSVP, a chrysanthemum (Chrysanthemum morifolium Ramat.) homolog of SVP, can repress the expression of a key flowering gene, a chrysanthemum FLOWERING LOCUS T-like gene (CmFTL3), by binding its promoter CArG element to delay flowering in the ambient temperature pathway in chrysanthemum. Protein-protein interaction assays identified an interaction between CmSVP and CmTPL1-2, a chrysanthemum homologue of TOPLESS (TPL) that plays critical roles as transcriptional corepressor in many aspects of plant life. Genetic analyses revealed the CmSVP-CmTPL1-2 transcriptional complex is a prerequisite for CmSVP to act as a floral repressor. Furthermore, overexpression of CmSVP rescued the phenotype of the svp-31 mutant in Arabidopsis (Arabidopsis thaliana), overexpression of AtSVP or CmSVP in the Arabidopsis dominant-negative mutation tpl-1 led to ineffective late flowering, and AtSVP interacted with AtTPL, confirming the conserved function of SVP in chrysanthemum and Arabidopsis. We have validated a conserved machinery wherein SVP partially relies on TPL to inhibit flowering via a thermosensory pathway.

The WD40 domain-containing protein Ehd5 positively regulates flowering in rice (Oryza sativa).

Heading date (flowering time), which greatly influences regional and seasonal adaptability in rice (Oryza sativa), is regulated by many genes in different photoperiod pathways. Here, we characterized a heading date gene, Early heading date 5 (Ehd5), using a modified bulked segregant analysis method. The ehd5 mutant showed late flowering under both short-day and long-day conditions, as well as reduced yield, compared to the wild type. Ehd5, which encodes a WD40 domain-containing protein, is induced by light and follows a circadian rhythm expression pattern. Transcriptome analysis revealed that Ehd5 acts upstream of the flowering genes Early heading date 1 (Ehd1), RICE FLOWERING LOCUS T 1 (RFT1), and Heading date 3a (Hd3a). Functional analysis showed that Ehd5 directly interacts with Rice outermost cell-specific gene 4 (Roc4) and Grain number, plant height, and heading date 8 (Ghd8), which might affect the formation of Ghd7-Ghd8 complexes, resulting in increased expression of Ehd1, Hd3a and RFT1. Taken together, these results demonstrate that Ehd5 functions as a positive regulator of rice flowering and provide insight into the molecular mechanisms underlying heading date.

Role of methylation in vernalization and photoperiod pathway: a potential flowering regulator?

Recognized as a pivotal developmental transition, flowering marks the continuation of a plant's life cycle. Vernalization and photoperiod are two major flowering pathways orchestrating numerous florigenic signals. Methylation, including histone, DNA and RNA methylation, is one of the recent foci in plant development. Considerable studies reveal that methylation seems to show an increasing potential regulatory role in plant flowering via altering relevant gene expression without altering the genetic basis. However, little has been reviewed about whether and how methylation acts on vernalization- and photoperiod-induced flowering before and after FLOWERING LOCUS C (FLC) reactivation, what role RNA methylation plays in vernalization- and photoperiod-induced flowering, how methylation participates simultaneously in both vernalization- and photoperiod-induced flowering, the heritability of methylation memory under the vernalization/photoperiod pathway, and whether and how methylation replaces vernalization/photoinduction to regulate flowering. Our review provides insight about the crosstalk among the genetic control of the flowering gene network, methylation (methyltransferases/demethylases) and external signals (cold, light, sRNA and phytohormones) in vernalization and photoperiod pathways. The existing evidence that RNA methylation may play a potential regulatory role in vernalization- and photoperiod-induced flowering has been gathered and represented for the first time. This review speculates about and discusses the possibility of substituting methylation for vernalization and photoinduction to promote flowering. Current evidence is utilized to discuss the possibility of future methylation reagents becoming flowering regulators at the molecular level.

Identifying genes regulated during natural, on-plant senescence in broccoli (Brassica oleracea) in contrast to postharvest senescence

The nutritional value of broccoli (Brassica oleracea L. var. Italica), its health benefits, as well as its economic value in world production make broccoli an ideal target for improvement given its current postharvest problems related to rapid senescence. Broccoli florets are harvested when their flowers are still developing and photosynthetically active. Harvest causes disruption of supply of water, hormones, nutrients, and energy, leads to imbalance of source-to-sink transition, and triggers stress-induced senescence. There is a clear gap in knowledge about the mechanisms of developmentally regulated, natural (on-plant) senescence and stress-induced postharvest senescence in broccoli. In this study, we aimed at elucidating the molecular mechanisms of natural (on-plant) senescence in broccoli in contrast to postharvest senescence. The genetic progression of natural senescence in broccoli florets was profiled in this study through the RNA-sequencing approach. Candidate genes were identified at each developmental stage of broccoli floret for the involvement of senescence by developmental signals. We further conducted comparative transcriptome analysis on those genes under developmentally regulated senescence and stress-induced postharvest senescence. We found that many genes behave differently in the two conditions, such as sugar transport family, senescence-associated genes (SAGs), ethylene biosynthesis and signaling genes, and flower senescence genes. A comparison of two SWEET family genes SWEET 3 and SWEET 9 in natural and postharvest senescence demonstrated opposite roles in source-sink transition in broccoli. Moreover, we found previously unreported transcription factors including stomatal patterning genes MUTE, SCREAM2, and FAMA and brassinosteroid signaling gene BR ENHANCED EXPRESSION 1 (BEE) that were regulated during natural senescence. In this research, we identified genes involved in natural senescence and further compared with postharvest senescence of commercial maturity broccoli to understand the dynamic senescence networks regulated by both developmental cues and stress signals.

LHD3 Encoding a J-Domain Protein Controls Heading Date in Rice

Heading date is one of the most important agronomic traits of rice, which critically affects rice ecogeographical adaptation, yield and quality. In this study, a late heading date 3 (lhd3) mutant was screened from the 60Co-γ irradiation mutant library. The lhd3 delayed heading date in rice under both short day and long day conditions. Map-based cloning combined with Mutmap strategy was adopted to isolate the causal LHD3 gene. The LHD3 gene encodes a DNA_J domain protein, which was ubiquitously expressed in various plant organs, and dominant expressed in stems and leaves. Subcellular localization analysis showed that LHD3 was localized to nucleus, indicating that LHD3 may interact with other elements to regulate the expression of flowering genes. The transcriptions of the heading activators Ehd1, Hd3a and RFT1 significantly decreased in the lhd3 mutant, suggesting that LHD3 may control the heading date through the Ehd1-Hd3a/RFT1 photoperiodic flowering pathway. The variation and haplotype analyses of the genomic region of LHD3 showed that there were 7 haplotypes in the LHD3 region from 4 702 accessions. The haplotypes of LHD3 can be divided into two classes: class a and class b, and the heading dates of these two classes were significantly different. Further study showed that two single nucleotide polymorphisms (SNPs), SNP10 (G2100C) in Hap II and SNP3 (C861T) in Hap VII, may be the functional sites causing early and late heading in accessions. Nucleotide diversity analysis showed LHD3 had been selected in the indica population, rather than in the japonica population. Therefore, the present study sheds light on the regulation of LHD3 on heading date in rice and suggests that LHD3 is a novel promising new target for rice molecular design and breeding improvement.

Functional analysis of WOX family genes in Dendrobium catenatum during growth and development.

The WUSCHEL-Related Homeobox (WOX) family is a group of transcription factors unique to plants that play an important role in regulating key developmental processes such as stem cell maintenance and organ morphogenesis. As a rare and valuable Chinese herb, Dendrobium catenatum has a unique epiphytic lifestyle and growth and developmental characteristics, and a functional investigation of its WOX family genes can help to further understand the conserved and specific development of D. catenatum. In this study, we analyzed the phylogeny, spatio-temporal expression pattern and heterologous expression function of D. catenatum WOX family genes (DcWOX). The results showed that members of the D. catenatum WOX gene family could be divided into three evolutionary branches with significantly different tissue expression profiles. In transgenic Arabidopsis, overexpression of DcWOX4 resulted in significant dwarfism, pinnately leaf margins, and delayed flowering for 2 weeks; overexpression of DcWOX9 resulted in plant dwarfing, serrated leaf margin, delayed flowering for 1 week, and even male and female sterility in strong phenotype plants; overexpression of DcWOX11 caused curl downward leaf. The abnormal morphogenesis of DcWOX4/9/11 overexpression Arabidopsis leaves are related to the down-regulation of TCP family genes, CUC family genes and the up-regulation of KNOX family genes; Postponement of flowering is related to down-regulation of early flowering genes such as FT, SOC1 and CO. Therefore, this study showed that D. catenatum WOX family genes have important functions in regulating plant morphogenesis, leaf development, flowering time and fertility, further expanding the understanding of the WOX gene family function, and providing clues for the conservation and specificity during orchid development and evolution.

XAANTAL1 Reveals an Additional Level of Flowering Regulation in the Shoot Apical Meristem in Response to Light and Increased Temperature in Arabidopsis.

Light and photoperiod are environmental signals that regulate flowering transition. In plants like Arabidopsis thaliana, this regulation relies on CONSTANS, a transcription factor that is negatively posttranslational regulated by phytochrome B during the morning, while it is stabilized by PHYA and cryptochromes 1/2 at the end of daylight hours. CO induces the expression of FT, whose protein travels from the leaves to the apical meristem, where it binds to FD to regulate some flowering genes. Although PHYB delays flowering, we show that light and PHYB positively regulate XAANTAL1 and other flowering genes in the shoot apices. Also, the genetic data indicate that XAL1 and FD participate in the same signaling pathway in flowering promotion when plants are grown under a long-day photoperiod at 22 °C. By contrast, XAL1 functions independently of FD or PIF4 to induce flowering at higher temperatures (27 °C), even under long days. Furthermore, XAL1 directly binds to FD, SOC1, LFY, and AP1 promoters. Our findings lead us to propose that light and temperature influence the floral network at the meristem level in a partially independent way of the signaling generated from the leaves.

Long non-coding RNA-mediated competing endogenous RNA regulatory network during flower development and color formation in Melastoma candidum.

M. candidum, an evergreen shrubby flower known for its superior adaptation ability in South China, has gained increased attention in garden applications. However, scant attention has been paid to its flower development and color formation process at the non-coding RNA level. To fill this gap, we conducted a comprehensive analysis based on long non-coding RNA sequencing (lncRNA-seq), RNA-seq, small RNA sequencing (sRNA-seq), and widely targeted metabolome detection of three different flower developmental stages of M. candidum. After differentially expressed lncRNAs (DElncRNAs), differentially expressed mRNAs (DEmRNAs), differentially expressed microRNAs (DEmiRNAs), and differentially synthesized metabolites (DSmets) analyses between the different flower developmental stages, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were conducted to identify some key genes and metabolites in flavonoid, flavone, anthocyanin, carotenoid, and alkaloid-related GO terms and biosynthetic pathways. Three direct-acting models, including antisense-acting, cis-acting, and trans-acting between lncRNAs and mRNAs, were detected to illustrate the direct function of lncRNAs on target genes during flower development and color formation. Based on the competitive endogenous RNA (ceRNA) regulatory theory, we constructed a lncRNA-mediated regulatory network composed of DElncRNAs, DEmiRNAs, DEmRNAs, and DSmets to elucidate the indirect role of lncRNAs in the flower development and color formation of M. candidum. By utilizing correlation analyses between DERNAs and DSmets within the ceRNA regulatory network, alongside verification trials of the ceRNA regulatory mechanism, the study successfully illustrated the significance of lncRNAs in flower development and color formation process. This research provides a foundation for improving and regulating flower color at the lncRNA level in M. candidum, and sheds light on the potential applications of non-coding RNA in studies of flower development.

Crops under past diversification and ongoing climate change: More than selection on nuclear genes for flowering.

Diversification and breeding following domestication and current climate change across the globe are the two most significant events experienced by major crops. Diversification of crops from their wild ancestors has favored dramatic changes in the plant's sensitivity to environment, significantly in transducing light inputs to the circadian clock, which allowed the growth of major crops in the shorter growing season in the Northern hemisphere. Historically, mutants and quantitative trait loci (QTL) mapping have facilitated the identification and cloning of genes underlying major changes of the clock and flowering regulation. Recent studies suggest that thermal plasticity of circadian clock output, not just the core genes that follow temperature compensation, was also under selection during diversification and breeding. Wild alleles that accelerate output rhythmicity could be beneficial for crop resilience. Furthermore, wild alleles with beneficial and flowering-independent effects under stress indicate their possible role in maintaining a balanced source-sink relationship, allowing productivity under climatic change. Because the chloroplast genome also regulates the plasticity of the clock output, mapping populations including cytonuclear interactions should be utilized in an integrated field and clock phenomics framework. We highlight the need to integrate physiological and developmental approaches (Physio-Devo) to gain a better understanding while re-domesticating wild gene alleles into modern cultivars to increase their robustness under abiotic heat and drought stresses.

The Significance of Florigen Activation Complex in Controlling Flowering in Rice

Yield potential, plant height and flowering time are three classes of traits that determine the productivity of rice. Rice heading greatly depends on the accurate measurement of environment changes, particularly in day length and temperature. We discuss all genes reported to be related to the heading time in this review. The accumulation of florigen, such as Hd3a or RFT1, is the key factor for rice heading. Florigen is found in the rice leaf and then transports into the shoot apical meristem (SAM), where floral initiation occurs. We discuss the formation of florigen activation complex (FAC) with 14-3-3 and FD1 proteins to induce the expression of flowering genes. In addition, two key pathways related to heading date, GI-Hd1-Hd3a and Ghd7-Ehd1-Hd3a/RFT1 are introduced in this review. We summarize proteins with histone modification functions, due to the modification of histone is also significant for heading date. The flowering time also extremely dependent on the environments, including nutrient availability, abiotic and biotic stresses, we argue the phenotypes of rice heading date under different extreme environments, as well. Lastly, we gather genes that are reported having a change in heading time, but their detail molecular regulation is still elusive. Thus, this review introduces heading time systematically, providing knowledge and ideas for researchers to study further the phenotype of heading time.

Methylome and transcriptome analysis of flowering branches building of Citrus plants induced by drought stress

Citrus plants exhibit positive floral response under water stress conditions, however, the mechanistic understanding of floral induction remains largely unexplored in water deficit. In this study, DNA methylomic and transcriptomic analyses were integrated to explore the flowering bud formation as well as branches building after light drought stress. While comparing with the conventional watering group (CK), the light drought group treated with five months (LD) showed a significant increase in the flowering branches, whereas an apparent decrease in vegetative branches. Global DNA methylation analysis showed that the LD Group acquired DNA methylation in more than 70,090 genomic regions and lost DNA methylation in about 18,421 genomic regions compared with normal watering group, this indicates that water deficiency leads to a global increase in the expression of DNA methylation in citrus. In the same time, we verified that the increase of DNA methylation level in LD group was correlated with the decrease of DNA demethylase related gene expression.Interestingly, in transcription analysis, it was found that the promoting flower genes of the LD group did not increase but decreased similarly with repressing genes, which is contrary to the intended result. Thus, we thought the lower expression of suppressors FLC and BFT were the key influencing factor to stimulate the flowering branches formation after LD treatment. Moreover, there was a strong negative correlation between the genes expression level and methylation level of the flowering induction/flower development genes. In general, we thought high global DNA methylation level induced by water deficit regulate the flowering branches building by reducing FLC and BFT genes expression.

Identification of Floral Volatile Components and Expression Analysis of Controlling Gene in Paeonia ostii 'Fengdan' under Different Cultivation Conditions.

In order to explore the release rule of floral volatile substances and the diurnal variation of different flower development stages of Paeonia ostii 'Fengdan' in potted and ground-planted conditions, dynamic headspace adsorption combined with gas chromatography-mass spectrometry(GC-MS) was used to analyze the dynamic changes in floral volatile components and contents. Quantitative real-time PCR (qRT-PCR) was used to analyze changes in flower fragrance-regulating genes PsPAL, PsTPSs, and PsbHLH at different flower development stages and a daily change process at the full-blooming stage. The results show that there were differences in aroma components and contents of Paeonia ostii 'Fengdan' at different flower development stages and different time quantum of every day. There were 25 and 28 aroma components identified in 7 flower development stages of tree peonies planted in pots and in the field, respectively, and 23 and 22 aroma components identified at different time quantum of the day, of which the largest and highest content was alkanes. The main characteristic aroma substances were (E)-β-ocimene, 1,3,5-trimethoxybenzene, 2,4-di-tert-butylphenol, methyl jasmonate, nerol, and cinnamyl alcohol; released amounts of the abovementioned substances varied depending on the development stage and the time of the day. The expression of flower fragrance-controlling genes (PsPAL, PsTPSs, and PsbHLH) in tree peonies varied greatly in different conditions. The results of this study provide a valuable resource to investigate floral fragrance formation in tree peonies.

How flower development genes were identified using forward genetic screens in Arabidopsis thaliana.

In the later part of the 1980s, the time was ripe for identifying genes controlling flower development. In that pregenomic era, the easiest way to do this was to induce random mutations in seeds by chemical mutagens (or irradiation) and to screen thousands of plants for those with phenotypes specifically defective in floral morphogenesis. Here, we discuss the results of premolecular screens for flower development mutants in Arabidopsis thaliana, carried out at Caltech and Monash University, emphasizing the usefulness of saturation mutagenesis, multiple alleles to identify full loss-of-function, conclusions based on multiple mutant analyses, and from screens for enhancer and suppressor modifiers of original mutant phenotypes. One outcome was a series of mutants that led to the ABC floral organ identity model (AP1, AP2, AP3, PI, and AG). In addition, genes controlling flower meristem identity (AP1, CAL, and LFY), floral meristem size (CLV1 and CLV3), development of individual floral organ types (CRC, SPT, and PTL), and inflorescence meristem properties (TFL1, PIN1, and PID) were defined. These occurrences formed targets for cloning that eventually helped lead to an understanding of transcriptional control of the identity of floral organs and flower meristems, signaling within meristems, and the role of auxin in initiating floral organogenesis. These findings in Arabidopsis are now being applied to investigate how orthologous and paralogous genes act in other flowering plants, allowing us to wander in the fertile fields of evo-devo.

Gibberellin signaling modulates flowering via the DELLA-BRAHMA-NF-YC module in Arabidopsis.

Gibberellin (GA) plays a key role in floral induction by activating the expression of floral integrator genes in plants, but the epigenetic regulatory mechanisms underlying this process remain unclear. Here, we show that BRAHMA (BRM), a core subunit of the chromatin-remodeling SWItch/sucrose nonfermentable (SWI/SNF) complex that functions in various biological processes by regulating gene expression, is involved in GA-signaling-mediated flowering via the formation of the DELLA-BRM-NF-YC module in Arabidopsis (Arabidopsis thaliana). DELLA, BRM, and NF-YC transcription factors interact with one another, and DELLA proteins promote the physical interaction between BRM and NF-YC proteins. This impairs the binding of NF-YCs to SOC1, a major floral integrator gene, to inhibit flowering. On the other hand, DELLA proteins also facilitate the binding of BRM to SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1). The GA-induced degradation of DELLA proteins disturbs the DELLA-BRM-NF-YC module, prevents BRM from inhibiting NF-YCs, and decreases the DNA-binding ability of BRM, which promote the deposition of H3K4me3 on SOC1 chromatin, leading to early flowering. Collectively, our findings show that BRM is a key epigenetic partner of DELLA proteins during the floral transition. Moreover, they provide molecular insights into how GA signaling coordinates an epigenetic factor with a transcription factor to regulate the expression of a flowering gene and flowering in plants.

Identification of SNPs Associated with Grain Quality Traits in Spring Barley Collection Grown in Southeastern Kazakhstan

Barley (Hordeum vulgare L.) is an important cereal crop with high genome plasticity that is cultivated in all climatic zones. Traditionally, barley grain is used for animal feed, malting, brewing, and food production. Depending on the end-use product, there are individual requirements for the quality traits of barley grain, particularly for raw starch and protein contents. This study evaluates a collection of 406 two-rowed spring barley accessions, comprising cultivars and lines from the USA, Kazakhstan, Europe, and Africa, based on five grain quality traits (the contents of raw starch, protein, cellulose, and lipids, and grain test weight) over two years. The results of population structure analysis demonstrate the significant impact of geographical origin on the formation of subclusters in the studied population. It was also found that the environment significantly affects grain quality traits. Heat and drought stresses, particularly during grain filling, led to higher protein and lower starch contents. A genome-wide association study (GWAS) using a multiple-locus mixed linear model (MLMM) allowed for the identification of 26 significant quantitative trait loci (QTLs) for the five studied grain quality traits. Among them, 17 QTLs were found to be positioned close to known genes and previously reported QTLs for grain quality in the scientific literature. Most of the identified candidate genes were dehydration stress and flowering genes, confirming that exposure to heat and drought stresses during grain filling may lead to dramatic changes in grain quality traits, including lower starch and higher protein contents. Nine QTLs were presumably novel and could be used for gene mining and breeding activities, including marker-assisted selection to improve grain quality parameters.

PhCHS5 and PhF3'5'H Genes Over-Expression in Petunia (Petunia hybrida) and Phalaenopsis (Phalaenopsis aphrodite) Regulate Flower Color and Branch Number.

Flower breeders are continually refining their methods for producing high-quality flowers. Phalaenopsis species are considered the most important commercially grown orchids. Advances in genetic engineering technology have provided researchers with new tools that can be used along with traditional breeding methods to enhance floral traits and quality. However, the application of molecular techniques for the breeding of new Phalaenopsis species has been relatively rare. In this study, we constructed recombinant plasmids carrying flower color-related genes, Phalaenopsis Chalcone synthase (PhCHS5) and/or Flavonoid 3',5'-hydroxylase (PhF3'5'H). These genes were transformed into both Petunia and Phalaenopsis plants using a gene gun or an Agrobacterium tumefaciens-based method. Compared with WT, 35S::PhCHS5 and 35S::PhF3'5'H both had deeper color and higher anthocyanin content in Petunia plants. Additionally, a phenotypic comparison with wild-type controls indicated the PhCHS5 or PhF3'5'H-transgenic Phalaenopsis produced more branches, petals, and labial petals. Moreover, PhCHS5 or PhF3'5'H-transgenic Phalaenopsis both showed deepened lip color, compared with the control. However, the intensity of the coloration of the Phalaenopsis lips decreased when protocorms were co-transformed with both PhCHS5 and PhF3'5'H. The results of this study confirm that PhCHS5 and PhF3'5'H affect flower color in Phalaenopsis and may be relevant for the breeding of new orchid varieties with desirable flowering traits.

The phased chromosome-scale genome of yellowhorn sheds light on the mechanism of petal color change

Yellowhorn (Xanthoceras sorbifolium), especially its varieties, is the red petal yellowhorn (X. sorbifolium var. purpurea), an important tree species with great ornamental value, and its flower petals change color throughout the flowering period. In this study, we mainly focused on the mechanism of the petal color change with transcriptomics and metabolomics data. A phased chromosome-scale assembly of the red petal yellowhorn genome was generated using the PacBio high-fidelity reads, Illumina short reads, and Phase genomics Proximo Hi-C data. The final de novo assembly yielded 533.67 Mb with a contig N50 of 5.42 Mb, and 27 501 protein-coding genes were predicted. Notably, an alternate haplotig assembly was also obtained. Furthermore, a variation database for the alleles within the genome was constructed. Subsequently, the expression pattern of flower pigmentation-related genes and allelic expression imbalance events were investigated. Apart from 6 genes involved in the anthocyanin biosynthesis pathway regulated by the activation of 15 MYB-bHLH-WD40s, the increased expression of senescence-related gene 1 (SRG1) and 2-oxoglutarate-dependent dioxygenase (DIOX5) might also result in decreasing content of lutein and increasing abundance of (E/Z)-phytoene, cyanidin-3-O-rutinoside, and cyanidin-3-O-sambubioside. These changes in genes and metabolites were most likely related to the petal color change in red petal yellowhorn. This phased chromosome-scale genome assembly provides more accurate genomic information for future molecular breeding and facilitates allele function studies of the red petal yellowhorn.

Responsiveness to long days for flowering is reduced in Arabidopsis by yearly variation in growing season temperatures.

Conservative flowering behaviours, such as flowering during long days in summer or late flowering at a high leaf number, are often proposed to protect against variable winter and spring temperatures which lead to frost damage if premature flowering occurs. Yet, due the many factors in natural environments relative to the number of individuals compared, assessing which climate characteristics drive these flowering traits has been difficult. We applied a multidisciplinary approach to 10winter-annual Arabidopsis thaliana populations from a wide climactic gradient in Norway. We used a variable reduction strategy to assess which of 100 climate descriptors from their home sites correlated most to their flowering behaviours when tested for responsiveness to photoperiod after saturation of vernalization; then, assessed sequence variation of 19 known environmental-response flowering genes. Photoperiod responsiveness inversely correlated with interannual variation in timing of growing season onset. Time to flowering appeared driven by growing season length, curtailed by cold fall temperatures. The distribution of FLM, TFL2and HOS1 haplotypes, genes involved in ambient temperature response, correlated with growing-season climate. We show that long-day responsiveness and late flowering may be driven not by risk of spring frosts, but by growing season temperature and length, perhaps to opportunistically maximize growth.

Rice OsMRG702 and Its Partner OsMRGBP Control Flowering Time through H4 Acetylation.

MORF-RELATED GENE702 (OsMRG702) regulates flowering time genes in rice, but how it controls transcription is not well known. Here, we found that OsMRGBP can directly interact with OsMRG702. Both Osmrg702 and Osmrgbp mutants show the delayed flowering phenotype with the reduction in the transcription of multiple key flowering time genes, including Ehd1 and RFT1. Chromatin immunoprecipitation study showed that both OsMRG702 and OsMRGBP bind to the Ehd1 and RFT1 loci and the absence of either OsMRG702 or OsMRGBP leads to a decrease of H4K5 acetylation at these loci, indicating OsMRG702 and OsMRGBP cooperatively together to promote the H4K5 acetylation. In addition, whilst Ghd7 are upregulated in both Osmrg702 and Osmrgbp mutants, only OsMRG702 binds to the loci, together with the global increased and Ghd7 locus-specific increased H4K5ac levels in Osmrg702 mutants, suggesting an additional negative effect of OsMRG702 on H4K5 acetylation. In summary, OsMRG702 controls flowering gene regulation by altering H4 acetylation in rice; it works either together with OsMRGBP to enhance transcription by promoting H4 acetylation or with other unknown mechanisms to dampen transcription by preventing H4 acetylation.

Exploring Flowering Genes in Phalaenopsis through Transcriptome Analysis and Critical Gene Validation of Hormone Signal Transduction Pathway

Exploring Flowering Genes in Phalaenopsis through Transcriptome Analysis and Critical Gene Validation of Hormone Signal Transduction Pathway