Flowering Phenotype Research Articles

GhASHH1.A and GhASHH2.A Improve Tolerance to High and Low Temperatures and Accelerate the Flowering Response to Temperature in Upland Cotton (Gossypium hirsutum).

The trithorax group (TrxG) complex is an important protein in the regulation of plant histone methylation. The ABSENT, SMALL, OR HOMEOTIC DISCS 1 (ASH1) gene family, as important family members of the TrxG complex, has been shown to regulate tolerance to abiotic stress and growth and development in many plants. In this study, we identified nine GhASH1s in upland cotton. Bioinformatics analysis revealed that GhASH1s contain a variety of cis-acting elements related to stress resistance and growth and development. The transcriptome expression profiles revealed that GhASHH1.A and GhASHH2.A genes expression were upregulated in flower organs and in response to external temperature stress. The results of virus-induced gene silencing (VIGS) indicated that GhASHH1.A and GhASHH2.A genes silencing reduced the ability of cotton to adapt to temperature stress and delayed the development of the flowering phenotype. We also showed that the silencing of these two target genes did not induce early flowering at high temperature (32 °C), suggesting that GhASHH1.A and GhASHH2.A might regulate cotton flowering in response to temperature. These findings provide genetic resources for future breeding of early-maturing and temperature-stress-tolerant cotton varieties.

Multi-Omics Revealed Regulatory Mechanisms Underlying the Flowering of Ferula sinkiangensis across Three Dimensions.

Backgroud/Objectives: Ferula spp. is an essential crop in Central Asia with pronounced economic benefits governed by its flowering process. However, the mechanisms of the flowering phenotype remain unclear. Methods: In this study, using F. sinkiangensis as a model plant, we integrated transcriptome, proteome, and metabolome analyses to compare the multilayer differences in leaves and roots of plants with flowering and unflowering phenotypes. Results: We found that several variations in the transcriptome, proteome, and metabolome were closely associated with flowering. The Photosynthesis and Phenylpropanoid biosynthesis pathways in plants with the flowering phenotype were more active. Additionally, three flowering genes, named FL2-FL4, were upregulated in the leaves of flowering plants. Notably, six transcription factors were potentially responsible for regulating the expression of FL2-FL4 in the leaves to mediate flowering process of F. sinkiangensis. Moreover, genes relevant to Photosynthesis and Phenylpropanoid biosynthesis were also involved in regulating the expression of FL2-FL4 in flowering plants. Conclusions: The active regulation network together with Photosynthesis and Phenylpropanoid biosynthesis were essential for inducing the expression of flowering-related genes in leaves to promote the flowering process of F. sinkiangensis.

ZmARF16 Regulates ZCN12 to Promote the Accumulation of Florigen and Accelerate Flowering.

Auxin response factors(ARFs) are a class of transcription factors that regulate the expression of auxin response genes and play a crucial role in plant growth and development. Florigen plays a crucial role in the process of flowering. However, the process by which auxin regulates the accumulation of florigen remains largely unclear. This study found that the expression of ZmARF16 in maize increases during flowering, and the genetic transformation of ZmARF16 accelerates the flowering process in Arabidopsis and maize. Furthermore, ZmARF16 was found to be positively correlated with the transcription of the ZCN12 gene. Similarly, the FT-like gene ZCN12 in maize rescues the late flowering phenotype of the FT mutation in Arabidopsis. Moreover, ZCN12 actively participates in the accumulation of florigen and the flowering process. Further research revealed that ZmARF16 positively responds to the auxin signal, and that the interaction between ZmARF16 and the ZCN12 promoter, as well as the subsequent promotion of ZCN12 gene expression, leads to early flowering. This was confirmed through a yeast one-hybrid and dual-luciferase assay. Therefore, the study provides evidence that the ZmARF16-ZCN12 module plays a crucial role in regulating the flowering process of maize.

A Plant biostimulant prepared from Ascophyllum nodosum Induces Flowering by Regulating the MIR156-mediated Age Pathway in Arabidopsis.

Flowering, the change from vegetative development to the reproductive phase, represents a crucial and intricate stage in the life cycle of plants, which is tightly controlled by both internal and external factors. In this study, we investigated the effect of Ascophyllum nodosum extract (ANE) on the flowering time of Arabidopsis. We found that a 0.1% concentration of ANE induced flowering in Arabidopsis, accompanied by the upregulation of key flowering time genes: FT (FLOWERING LOCUS T), SOC1 (SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1), and LFY (LEAFY). Further investigation showed that ANE specifically promotes flowering through the MIR156-mediated age pathway. ANE treatment resulted in the repression of negative regulator genes, MIR156, while simultaneously enhancing the expression of positive regulator genes, including SPLs and MIR172. This, in turn, led to the downregulation of AP2-like genes, which are known as floral repressors. It is worth noting that ANE did not alleviate the late flowering phenotype of MIR156-overexpressing plants and spl mutants. Furthermore, ANE-derived fucoidan mimics the function of sugars in regulating MIR156, closely mirroring the effects induced by ANE treatments. It suppresses the transcript levels of MIR156 and AP2-like genes while inducing those of SPLs and MIR172, thereby reinforcing the involvement of fucoidan in the control of flowering by ANE. In summary, our results demonstrate that ANE induces flowering by modulating the MIR156-SPL module within the age pathway, and this effect is mediated by fucoidan.

The RING-type E3 ligase, TaFRFP, regulates flowering by controlling a salicylic acid-mediated floral promotion

The initiation of transition to flowering is carefully managed by endogenous and environmental cues, which is critical for flowering plant reproductive success. Here, we found that wheat RING-type E3 ligase TaFRFP was highly expressed from the double ridge to degeneration stage (WS2.5-WS9). TaFRFP is localized in the nucleus and has E3 ligase activity in vitro. TaFRFP overexpression in Arabidopsis resulted in an early flowering phenotype, but to a lesser extent, under short-day conditions. Under the SA-treated condition, overexpression of TaFRFP shows higher root growth and has more accumulation of SA contents. A proteomic comparison revealed that the amount of FRL4A protein, a FRIGIDA LIKE 4 A, was considerably lower in SA-treated TaFRFP seedlings compared to normal condition. We further found that TaFRFP directly interacts with FRL4A in the nucleus and recruits it to the FLC locus in Arabidopsis. Moreover, an ubiquitination assay showed that TaFRPF physically interact and ubiquitinates TaFRL as a substrate. Our findings support the concept that the TaFRFP E3 ligase works as a positive regulator, and that the ubiquitination of its substrate proteins plays a significant role in controlling flowering time via an SA-dependent pathway.

Multiplex Approach of Metabolomic and Transcriptomic Reveals the Biosynthetic Mechanism of Light-induced Flavonoids and CGA in Chrysanthemum

Light, as an important environmental signal for plant growth and development, has been reported to be involved in the metabolism of phenylpropane. However, the light-induced phenylpropane biosynthesis mechanism in Chrysanthemum morifolium Ramat., especially flavonoid and chlorogenic acid (CGA) metabolism, is not clear. In this study, we found the flower phenotype of chrysanthemum 'HangBaiJu' became lighter after bagging. Besides, the content of main active ingredients, such as Luteolin-7-O-glucoside (Lu-7-O-G), Diosmetin-7-O-glucoside (Di-7-O-G), Apigenin-7-O-glucoside, Apigenin and CGA, was significantly decreased. Comparative transcriptome analysis (pairwise comparison, WGCNA, and k-means clustering) revealed that the expression of structural genes, such as CmPAL, CmCHS1/2, CmF3’H, CmFNS and CmHQT, was notably declined under dark conditions. Meanwhile, ‘bridge proteins’ CmMYB3/6/16 and signal transduction factors CmBBX20/22.2/22.3 were identified as key regulatory factors in the light-mediated synthesis of flavonoids and CGA in chrysanthemum. Among that, CmBBX20 could promote the accumulation of flavonoids and CGA by directly binding to the G-box core sequences of downstream target genes based on transient overexpression and Y1H assays. Overall, the preliminary molecular mechanism of BBXs and MYBs coordinately regulating the accumulation of flavonoids and CGA in chrysanthemum under different light inductions has been clarified, which provided a theoretical basis for the molecular breeding and quality improvement of chrysanthemum.

Improving Rice Quality by Regulating the Heading Dates of Rice Varieties without Yield Penalties.

The heading date, a critical trait influencing the rice yield and quality, has always been a hot topic in breeding research. Appropriately delaying the flowering time of excellent northern rice varieties is of great significance for improving yields and enhancing regional adaptability during the process for introducing varieties from north to south. In this study, genes influencing the heading date were identified through genome-wide association studies (GWAS). Using KenDao 12 (K12), an excellent cultivar from northern China, as the material, the specific flowering activator, OsMADS50, was edited using the genome-editing method to regulate the heading date to adapt to the southern planting environment. The results indicated that the osmads50 mutant line of K12 flowered about a week later, with a slight increase in the yield and good adaptability in the southern region in China. Additionally, the expressions of key flowering regulatory genes, such as Hd1, Ghd7, Ehd1, Hd3a, and RFT1, were reduced in the mutant plants, corroborating the delayed flowering phenotype. Yield trait analysis revealed that the primary factor for improved yield was an increase in the number of effective tillers, although there is potential for further enhancements in the seed-setting rate and grain plumpness. Furthermore, there were significant increases in the length-to-width ratio of the rice grains, fat content, and seed transparency, all contributing to an overall improvement in the rice quality. In summary, this study successfully obtained a rice variety with a delayed growth period through OsMADS50 gene editing, effectively implementing the strategy for adapting northern rice varieties to southern climates. This achievement significantly supports efforts to enhance the rice yield and quality as well as to optimize production management practices.

GhSWEET42 Regulates Flowering Time under Long-Day Conditions in Arabidopsis thaliana.

Flowering in plants is pivotal for initiating and advancing reproductive processes, impacting regional adaptation and crop yield. Despite numerous cloned and identified flowering time genes, research in cotton remains sparse. This study identified GhSWEET42 as a key determinant of the flowering time in cotton, demonstrating that its heterologous expression in Arabidopsis accelerated flowering under LD conditions compared to WT. Transgenic plants exhibited upregulated expression of the flowering inducers AtFT, AtSOC1, AtGI, and AtFKF1, alongside downregulated expression of the repressors AtTSF, AtFLC, and AtRGL2, correlating with the earlier flowering phenotype. GhSWEET42 showed a constitutive expression pattern, with elevated levels in the leaves, petals, and flower buds, and was notably higher in early-maturing cotton varieties. Subcellular localization assays confirmed GhSWEET42's presence on the cell membrane. Transcriptome analysis between WT and GhSWEET42-overexpressing Arabidopsis plants revealed 2393 differentially expressed genes (DEGs), spanning 221 biological processes, 93 molecular functions, and 37 cellular components according to Gene Ontology (GO) enrichment analysis. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis categorized the DEGs into metabolism and environmental information processing. These findings enhance the understanding of GhSWEET42's function and provide a foundation for elucidating the molecular mechanisms governing flowering time regulation in cotton.

Orphan gene BR2 positively regulates bolting resistance through the vernalization pathway in Chinese cabbage.

Orphan genes (OGs) are unique to the specific species or lineage, and whose homologous sequences cannot be found in other species or lineages. Furthermore, these genes lack recognizable domains or functional motifs, which make their characterization difficult. Here, we identified a Brassica rapa OG named BOLTING RESISTANCE 2 (BR2) that could positively modulate bolting resistance. The expression of BR2 was developmentally regulated and the BR2 protein was localized to the cell membrane. BR2 overexpression not only markedly delayed flowering time in Arabidopsis transgenic plants, but substantially affected the development of leaves and flower organs. Flowering repressor AtFLC gene was significantly up-regulated transcribed in Arabidopsis BR2 overexpression lines, while AtFT and AtSOC1 expression was decreased. In addition, the BR2 expression was enhanced in bolting-resistant type Chinese cabbage and was reduced in non-resistant type. Moreover, chilling stress inhibited the BR2 expression levels. Overexpression of BR2 also delayed flowering time in Chinese cabbage. In vernalized Chinese cabbage BR2 overexpression plants, BrVIN3.b and BrFRI were significantly down-regulated, while BrFLC5 was substantially up-regulated. Key floral factors, including three BrSOC1s, two BrLFYs, and four BrFTs were down-regulated. The expression changes of these key genes were consistent with the delayed flowering phenotype of Chinese cabbage BR2 overexpressing plants. Thus, we predicted that BR2 may predominantly function via the vernalization pathway. Our findings propose that the OG BR2 acts as a novel modulator of flowering time in Chinese cabbage, which provides a new insight on the breeding of varieties that are resistant to bolting.

Molecular cloning and characterization of FLOWERING LOCUS T (FT)gene from kinnow mandarin (Citrus reticulata)

FLOWERING LOCUS T (FT) is considered as a crucial regulator involved in early flowering induction which functions by switching the vegetative phase into reproductive phase. The role of early flowering has been elucidated by many workers but till date, there has been no report on cloning of FT gene from Kinnow mandarin (Citrus reticulata Blanco). An experiment was conducted during 2022–23 at Punjab Agricultural University, Ludhiana, Punjab for molecular cloning and characterization of FT gene from Kinnow mandarin. During the study, FT gene was cloned into pGEM-T Easy vector and characterized using in silico analysis. Sequence analysis revealed that the FT gene is comprised of 822 nucleotides, including a 5’- untranslated region (UTR) of 137 bp, a coding sequence (CDS) of 534 bp, and a 3’-UTR region of 151 bp. The BLASTn results of CrFT CDS showed high similarity to FT-like genes of other citrus species including C. unshiu, C. sinensis, and C. clementina which were found homologous to Phosphatidylethanolamine binding protein (PEBP). The predicted molecular weight of protein was approximately 20 kDa and isoelectric point (pI) was 6.73 indicating slightly acidic nature of the protein. The instability, aliphatic and GRAVY (Grand Average of Hydropathy) indices of the protein were determined as 40.97, 73.16 and -0.491, respectively. This study would help to elucidate the molecular mechanism behind flowering in Kinnow mandarin and facilitate the molecular breeding studies targeted to obtain early flowering phenotypes.

Melon CmRLCK VII-8 kinase genes CmRLCK27, CmRLCK30 and CmRLCK34 modulate resistance against bacterial and fungal diseases in Arabidopsis.

Receptor-like cytoplasmic kinases (RLCKs) represent a distinct class of receptor-like kinases crucial for various aspects of plant biology, including growth, development, and stress responses. This study delves into the characterization of RLCK VII-8 members within cucurbits, particularly in melon, examining both structural features and the phylogenetic relationships of these genes/proteins. The investigation extends to their potential involvement in disease resistance by employing ectopic overexpression in Arabidopsis. The promoters of CmRLCK VII-8 genes harbor multiple phytohormone- and stress-responsive cis-acting elements, with the majority (excluding CmRLCK39) displaying upregulated expression in response to defense hormones and fungal infection. Subcellular localization studies reveal that CmRLCK VII-8 proteins predominantly reside on the plasma membrane, with CmRLCK29 and CmRLCK30 exhibiting additional nuclear distribution. Notably, Arabidopsis plants overexpressing CmRLCK30 manifest dwarfing and delayed flowering phenotypes. Overexpression of CmRLCK27, CmRLCK30, and CmRLCK34 in Arabidopsis imparts enhanced resistance against Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000, concomitant with the strengthened expression of defense genes and reactive oxygen species accumulation. The CmRLCK VII-8 members actively participate in chitin- and flg22-triggered immune responses. Furthermore, CmRLCK30 interacts with CmMAPKKK1 and CmARFGAP, adding a layer of complexity to the regulatory network. In summary, this functional characterization underscores the regulatory roles of CmRLCK27, CmRLCK30, and CmRLCK34 in immune responses by influencing pathogen-induced defense gene expression and ROS accumulation.

Functional divergence of FTL9 and FTL10 in flowering control in rice

BackgroundFloral transition in cereals is a critical phenomenon influenced by exogenous and endogenous signals, determining crop yield and reproduction. Flowering Locus T-like (FT-like) genes encode a mobile florigen, the main signaling molecule for flowering.ResultsIn this study, we characterized two FT-like genes, FTL9 and FTL10, to study their functional diversity in flowering control in rice. We compared independent mutant lines of ftl10 with WT and observed negligible differences in the flowering phenotype, or agronomic traits implying potentially redundant roles of FTL10 loss-of-function in flowering control in rice. Nevertheless, we found that overexpression of FTL10, but not FTL9, substantially accelerated flowering, indicating the flowering-promoting role of FTL10 and the divergent functions between FTL9 and FTL10 in flowering. Besides flowering, additive agronomic roles were observed for FTL10-OE regulating the number of effective panicles per plant, the number of primary branches per panicle, and spikelets per panicle without regulating seed size. Mechanistically, our Y2H and BiFC analyses demonstrate that FTL10, in contrast to FTL9, can interact with FD1 and GF14c, forming a flowering activation complex and thereby regulating flowering.ConclusionAltogether, our results elucidate the regulatory roles of FTL9 and FTL10 in flowering control, unveiling the molecular basis of functional divergence between FTL10 and FTL9, which provides mechanistic insights into shaping the dynamics of flowering time regulation in rice.

MIKC type MADS-box transcription factor LcSVP2 is involved in dormancy regulation of the terminal buds in evergreen perennial litchi (Litchi chinensis Sonn.).

SHORT VEGETATIVE PHASE (SVP), a member of the MADS-box transcription factor family, has been reported to regulate bud dormancy in deciduous perennial plants. Previously, three LcSVPs (LcSVP1, LcSVP2 and LcSVP3) were identified from litchi genome, and LcSVP2 was highly expressed in the terminal buds of litchi during growth cessation or dormancy stages and down-regulated during growth stages. In this study, the role of LcSVP2 in governing litchi bud dormancy was examined. LcSVP2 was highly expressed in the shoots, especially in the terminal buds at growth cessation stage, whereas low expression was showed in roots, female flowers and seeds. LcSVP2 was found to be located in the nucleus and have transcription inhibitory activity. Overexpression of LcSVP2 in Arabidopsis thaliana resulted in a later flowering phenotype compared to the wild-type control. Silencing LcSVP2 in growing litchi terminal buds delayed re-entry of dormancy, resulting in significantly lower dormancy rate. The treatment also significantly up-regulated litchi FLOWERING LOCUS T2 (LcFT2). Further study indicates that LcSVP2 interacts with an AP2-type transcription factor, SMALL ORGAN SIZE1 (LcSMOS1). Silencing LcSMOS1 promoted budbreak and delayed bud dormancy. Abscisic acid (200mg/L), which enforced bud dormancy, induced a short-term increase in the expression of LcSVP2 and LcSMOS1. Our study reveals that LcSVP2 may play a crucial role, likely together with LcSMOS1, in dormancy onset of the terminal bud and may also serve as a flowering repressor in evergreen perennial litchi.

Genome-wide identification of the plant homeodomain-finger family in rye and ScPHD5 functions in cold tolerance and flowering time.

111 PHD genes were newly identified in rye genome and ScPHD5's role in regulating cold tolerance and flowering time was suggested. Plant homeodomain (PHD)-finger proteins regulate the physical properties of chromatin and control plant development and stress tolerance. Although rye (Secale cereale L.) is a major winter crop, PHD-finger proteins in rye have not been studied. Here, we identified 111 PHD genes in the rye genome that exhibited diverse gene and protein sequence structures. Phylogenetic tree analysis revealed that PHDs were genetically close in monocots and diverged from those in dicots. Duplication and synteny analyses demonstrated that ScPHDs have undergone several duplications during evolution and that high synteny is conserved among the Triticeae species. Tissue-specific and abiotic stress-responsive gene expression analyses indicated that ScPHDs were highly expressed in spikelets and developing seeds and were responsive to cold and drought stress. One of these genes, ScPHD5, was selected for further functional characterization. ScPHD5 was highly expressed in the spike tissues and was localized in the nuclei of rye protoplasts and tobacco leaves. ScPHD5-overexpressing Brachypodium was more tolerant to freezing stress than wild-type (WT), with increased CBF and COR gene expression. Additionally, these transgenic plants displayed an extremely early flowering phenotype that flowered more than two weeks earlier than the WT, and vernalization genes, rather than photoperiod genes, were increased in the WT. RNA-seq analysis revealed that diverse stress response genes, including HSPs, HSFs, LEAs, and MADS-box genes, were also upregulated in transgenic plants. Our study will help elucidate the roles of PHD genes in plant development and abiotic stress tolerance in rye.

An auxin regulated Universal stress protein (TaUSP_3B-1) interacts with TaGolS and provides tolerance under drought stress and ER stress.

A previously identified wheat drought stress responsive Universal stress protein, TaUSP_3B-1 has been found to work in an auxin dependent manner in the plant root tissues in the differentiation zone. We also found a novel interacting partner, TaGolS, which physically interacts with TaUSP_3B-1 and colocalizes in the endoplasmic reticulum. TaGolS is a key enzyme in the RFO (Raffinose oligosaccharides) biosynthesis which is well reported to provide tolerance under water deficit conditions. TaUSP_3B-1 overexpression lines showed an early flowering phenotype under drought stress which might be attributed to the increased levels of AtTPPB and AtTPS transcripts under drought stress. Moreover, at the cellular levels ER stress induced TaUSP_3B-1 transcription and provides tolerance in both adaptive and acute ER stress via less ROS accumulation in the overexpression lines. TaUSP_3B-1 overexpression plants had increased silique numbers and a denser root architecture as compared to the WT plants under drought stress.

Phenotypic selection patterns in a hybrid zone between two Calceolaria species with contrasting pollinators: insights from field surveys and fitness assessments.

Hybrid zones provide natural experimental settings to test hypotheses about species divergence. We concentrated on a hybrid swarm in which oil-collecting bees and flower-pecking birds act as pollinators of two Calceolaria species. We asked whether both pollinators contributed to flower divergence by differentially promoting prezygotic fitness at the phenotypic extremes that represent parentals. We studied pollinator-mediated selection on phenotypic traits critical in plant-pollinator mechanical interaction, namely plant height, reward-to-stigma distance, and flower shape. We utilised the quantity and quality of pollen deposited as fitness measures and distinguished between the contribution of the two pollinator types. Results showed uni- and bivariate disruptive selection for most traits through pollen grains deposited by both pollinators. Bird-mediated fitness favoured low plants with a long reward-to-stigma distance and a straight corolla, while bee-mediated fitness favoured tall plants with a short reward-to-stigma distance and curved corolla. In addition, stabilising selection at one end of the phenotypic range showed a bird-mediated reproductive asymmetry within the swarm. The disruptive pattern was countered, albeit weakly, by hybrids receiving higher-quality pollen on the stigmas. Results suggest that pollinator-mediated selection promotes divergence of integrated flower phenotypes mechanically adjusted either to bees or birds underscoring the importance of pollinator specialisation in diversification.

Nuclear factor Y-A3b binds to the SINGLE FLOWER TRUSS promoter and regulates flowering time in tomato.

The control of flowering time is essential for reproductive success and has a major effect on seed and fruit yield and other important agricultural traits in crops. Nuclear factors Y (NF-Ys) are transcription factors that form heterotrimeric protein complexes to regulate gene expression required for diverse biological processes, including flowering time control in plants. However, to our knowledge, there has been no report on mutants of individual NF-YA subunits that promote early flowering phenotype in plants. In this study, we identified SlNF-YA3b, encoding a member of the NF-Y transcription factor family, as a key gene regulating flowering time in tomato. Knockout of NF-YA3b resulted in an early flowering phenotype in tomato, whereas overexpression of NF-YA3b delayed flowering in transgenic tomato plants. NF-YA3b was demonstrated to form heterotrimeric protein complexes with multiple NF-YB/NF-YC heterodimers in yeast three-hybrid assays. Biochemical evidence indicated that NF-YA3b directly binds to the CCAAT cis-elements of the SINGLE FLOWER TRUSS (SFT) promoter to suppress its gene expression. These findings uncovered a critical role of NF-YA3b in regulating flowering time in tomato and could be applied to the management of flowering time in crops.

Transcriptome-Based Identification of Candidate Flowering-Associated Genes of Blueberry in a Plant Factory with Artificial Lighting (PFAL) under Short-Day-Length Conditions.

In blueberry (Vaccinium corymbosum L.), a perennial shrub, flower bud initiation is mediated by a short-day (SD) photoperiod and buds bloom once the chilling requirement is satisfied. A plant factory with artificial lighting (PFAL) is a planting system that can provide a stable and highly efficient growing environment for blueberry production. However, the characteristics of bud differentiation of blueberry plants inside PFAL systems are poorly understood. To better understand flower bud initiation and the flowering mechanism of blueberry in PFAL systems, the anatomical structure of apical buds under SD conditions in a PFAL system was observed using the southern highbush cultivar 'Misty' and a transcriptomic analysis was performed to identify the candidate flowering genes. The results indicated that the apical bud of 'Misty' differentiated gradually along with SD time course and swelled obviously when chilling was introduced. A total of 39.28 Gb clean data were generated, and about 20.31-24.11 Mb high-quality clean reads were assembled, yielding a total of 17370 differentially expressed genes (DEGs), of which 9637 were up-regulated and 7733 were down-regulated. Based on the functional annotation, 26 DEGs were identified including 20 flowering-related and 6 low-temperature DEGs, out of which the expressive level of four flowering-related DEGs (VcFT2, VcFPA, VcFMADS1, and VcCOP1) and two low-temperature-induced DEGs (VcTIL-1 and VcLTI 65-like) were confirmed by qRT-PCR with a good consistency with the pattern of transcriptome. Functional analysis indicated that VcFT2 was highly conserved with nuclear and cytoplasmic subcellular localization and was expressed mainly in blueberry leaf tissue. In Arabidopsis, ectopic overexpression of VcFT2 results in an early flowering phenotype, indicating that VcFT2 is a vital regulator of the SD-mediated flowering pathway in blueberry. These results contribute to the investigation of photoperiod-mediated flowering mechanisms of blueberry in PFAL systems.

Polymorphisms in two key anthocyanic genes of clivia (Clivia miniata L.) reveal evidence of selection and possible association with flower pigmentation.

Members of the genus Clivia show considerable variation in flower pigmentation and morphology. Such variation is affected by mutations that emerge in candidate flower development genes over time. Besides population history, mutations can further illuminate the effects of demographic events in populations in addition to population genetic parameters including selection, recombination, and linkage disequilibrium (LD). The current study aimed to find sequence variants in 2 anthocyanin biosynthetic genes (DFR and bHLH) of Clivia miniata and use the data to assess population genetic factors from a random collection of orange/red- and yellow-flowered specimens. Overall, average nucleotide diversity in the 2 anthocyanin genes was moderate (π = 0.00646), whereas haplotypes differed significantly (Hd ≥ 0.9). Gene evolution was seemingly driven by mutations (CmiDFR) or recombinations (CmibHLH001). LD decayed swiftly within the analyzed gene regions and supported the feasibility of assessing trait-variant associations via the association/linkage mapping approach. In the end, most associations were found to be spurious, but 1 haplotype in CmibHLH001 showed a promising correlation to the orange/red flower phenotype in Clivia specimens. In all, the present study is the first to measure gene-level diversity in C. miniata-data that had never been reported so far. Furthermore, the study also identified allelic and haplotypic variants that may be beneficial in future association genetic studies of Clivia. Such studies, however, consider large diverse populations to control for statistical bias intrinsic to the analysis of small datasets.

ATX1 and HUB1/2 promote recruitment of the transcription elongation factor VIP2 to modulate the floral transition in Arabidopsis.

Histone 2B ubiquitination (H2Bub) and trimethylation of H3 at lysine 4 (H3K4me3) are associated with transcription activation. However, the function of these modifications in transcription in plants remains largely unknown. Here, we report that coordination of H2Bub and H3K4me3 deposition with the binding of the RNA polymerase-associated factor VERNALIZATION INDEPENDENCE2 (VIP2) to FLOWERING LOCUS C (FLC) modulates flowering time in Arabidopsis. We found that RING domain protein HISTONE MONOUBIQUITINATION1 (HUB1) and HUB2 (we refer as HUB1/2), which are responsible for H2Bub, interact with ARABIDOPSIS TRITHORAX1 (ATX1), which is required for H3K4me3 deposition, to promote the transcription of FLC and repress the flowering time. The atx1-2 hub1-10 hub2-2 triple mutant in FRIGIDIA (FRI) background displayed early flowering like FRI hub1-10 hub2-2 and overexpression of ATX1 failed to rescue the early flowering phenotype of hub1-10 hub2-2. Mutations in HUB1 and HUB2 reduced the ATX1 enrichment at FLC, indicating that HUB1 and HUB2 are required for ATX1 recruitment and H3K4me3 deposition at FLC. We also found that the VIP2 directly binds to HUB1, HUB2, and ATX1 and that loss of VIP2 in FRI hub1-10 hub2-2 and FRI atx1-2 plants resulted in early flowering like that observed in FRI vip2-10. Loss of function of HUB2 and ATX1 impaired VIP2 enrichment at FLC, and reduced the transcription initiation and elongation of FLC. In addition, mutations in VIP2 reduced HUB1 and ATX1 enrichment and H2Bub and H3K4me3 levels at FLC. Together, our findings revealed that HUB1/2, ATX1, and VIP2 coordinately modulate H2Bub and H3K4me3 deposition, FLC transcription, and flowering time.