Regulation Of Flowering Research Articles

Transcriptome Analysis of Short-Day Photoperiod Inducement in Adzuki Bean (Vigna angularis L.) Based on RNA-Seq

The flowering characteristics of adzuki bean are influenced by several environmental factors. Light is an important ecological factor that induces flowering in adzuki bean, but to date, there have been few reports on the transcriptomic features of photoperiodic regulation of adzuki bean flowering. This study is based on RNA sequencing (RNA-seq) techniques to elucidate the expression of light-related regulatory genes under short-day photoperiod inducement of adzuki bean flowering, providing an important theoretical basis for its accelerated breeding. Short-day photoperiod inducement of 10 h was conducted for 5 day, 10 day, and 15 day periods on “Tang shan hong xiao dou” varieties, which are more sensitive to short-day photoperiod conditions than the other varieties. Plants grown under natural light (14.5 h) for 5 days, 10 days, and 15 days were used as controls to compare the progress of flower bud differentiation and flowering characteristics. The topmost unfolded functional leaves were selected for transcriptome sequencing and bioinformatics analysis. The short-day photoperiod inducement promoted flower bud differentiation and advanced flowering time in adzuki bean. Transcriptomic analysis revealed 5,608 differentially expressed genes (DEGs) for the combination of CK-5d vs. SD-5d, CK-10d vs. SD-10d, and CK-15d vs. SD-15d. The three groups of the DEGs were analyzed using the Gene Ontology (GO) and the Kyoto Encyclopedia of Genomes and Genomes (KEGG) databases; the DEGs were associated with flowering, photosystem, and the circadian rhythm and were mainly concentrated in the hormone signaling and metabolism, circadian rhythm, and antenna protein pathways; So, 13 light-related genes across the three pathways were screened for differential and expression characteristics. Through the functional annotations of orthologs, these genes were related to flowering, which were supposed to be good candidate genes in adzuki bean. The findings provide a deep understanding of the molecular mechanisms of adzuki bean flowering in response to short-day photoperiod inducement, which laid a foundation for the functional verification of genes in the next step, and provide an important reference for the molecular breeding of adzuki bean.

Functional divergence of GhAP1.1 and GhFUL2 associated with flowering regulation in upland cotton (Gossypium hirsutum L.)

The AP1/FUL transcription factors are important for floral development, but the underlying molecular mechanisms remain unclear. In this study, we cloned and identified two AP1/FUL-like genes, GhAP1.1 and GhFUL2, in upland cotton, which is a commonly cultivated economically valuable crop. Sequence alignment and phylogenetic analysis indicated that GhAP1.1 and GhFUL2, which are encoded by genes in the AP1/FUL clade, have conserved N-terminal regions but diverse C-terminal domains. Quantitative real-time PCR analysis revealed that GhAP1.1 and GhFUL2 were expressed in the flower and root, and showed opposite expression patterns during shoot apical meristem development. The upregulated expression of GhAP1.1 in Arabidopsis did not result in significant changes to the flowering time or floral organ development, and the transcript levels of the florigen FT increased and those of LFY decreased. Overexpression of GhFUL2 in Arabidopsis delayed flowering and promoted bolting by decreasing FT and LFY transcript levels. Silencing GhFUL2 in cotton dramatically increased the expression of GhFT and GhAP1.3 and promoted flowering. Yeast two-hybrid and bimolecular fluorescence complementation assays indicated that GhAP1.1 could interact with the SVP homolog GhSVP2.2, whereas GhFUL2 formed heterodimers with GhSEP3/GhSEP4 homologs and GhSVP2.2. The present results demonstrated that the functional divergence of GhAP1.1 and GhFUL2, which involved changes in sequences and expression patterns, influenced the regulation of cotton flower development.

Integrative Analyses of Transcriptomes and Metabolomes Reveal Associated Genes and Metabolites with Flowering Regulation in Common Vetch (Vicia sativa L.)

As an important source of protein for livestock and human consumption, Vicia sativa is cultivated worldwide, but its seed production is hampered at high altitudes because of the short frost-free period. Flowering represents the transition from a vegetative to a reproductive period, and early flowering benefits plant seed production at high altitudes. However, the molecular mechanisms of flowering regulation in V. sativa remain elusive. In the present study, two V. sativa accessions with different flowering characteristics were used: Lan3 (early-flowering) was cultivated by our laboratory, and 503 (late-flowering) was selected from 222 V. sativa accessions after three years of field experiments. The shoot samples (shoot tip length = 10 cm) of these two accessions were collected 63, 70, and 77 days after sowing, and the molecular regulatory mechanism of the flowering process was identified by integrative analyses of the transcriptomes and metabolomes. Kyoto Encyclopedia of Genes and Genomes enrichment showed that the synthesis and signal transduction of plant hormone pathways were the most enriched pathways in 4274 differentially expressed genes (DEGs) and in 259 differential metabolites between Lan3 and 503. Moreover, the contents of three metabolites related to salicylic acid biosynthesis and the transcription levels of two DEGs related to salicylic acid signal transduction in Lan3 were higher than those in 503. Further verification in various accessions indicated that salicylic acid metabolism may be involved in the flowering regulation process of V. sativa. These findings provide valuable information for understanding the flowering mechanism and for promoting breeding research in V. sativa.

WRKY63 transcriptional activation of COOLAIR and COLDAIR regulates vernalization-induced flowering.

Arabidopsis (Arabidopsis thaliana) FLOWERING LOCUS C (FLC) acts as a key flowering regulator by repressing the expression of the floral integrator FLOWERING LOCUS T (FT). Prolonged exposure to cold (vernalization) induces flowering by reducing FLC expression. The long noncoding RNAs (lncRNAs) COOLAIR and COLDAIR, which are transcribed from the 3' end and the first intron of FLC, respectively, are important for FLC repression under vernalization. However, the molecular mechanism of how COOLAIR and COLDAIR are transcriptionally activated remains elusive. In this study, we found that the group-III WRKY transcription factor WRKY63 can directly activate FLC. wrky63 mutant plants display an early flowering phenotype and are insensitive to vernalization. Interestingly, we found that WRKY63 can activate the expression of COOLAIR and COLDAIR by binding to their promoters.WRKY63 therefore acts as a dual regulator that activates FLC directly under non-vernalization conditions but represses FLC indirectly during vernalization through inducing COOLAIR and COLDAIR. Furthermore, genome-wide occupancy profile analyses indicated that the binding of WRKY63 to vernalization-induced genes increases after vernalization. In addition, WRKY63 binding is associated with decreased levels of the repressive marker Histone H3 Lysine 27 trimethylation (H3K27me3). Collectively, our results indicate that WRKY63 is an important flowering regulator involved in vernalization-induced transcriptional regulation.

Flower Regulation in Floriculture: An Agronomic Concept and Commercial Use

Flower Regulation in Floriculture: An Agronomic Concept and Commercial Use

WHIRLY1 recruits the histone deacetylase HDA15 repressing leaf senescence and flowering in Arabidopsis.

Leaf senescence is controlled by a complex regulatory network in which robustness is ensured by the activity of transcription factors and epigenetic regulators. However, how these coordinate the process of leaf senescence remains poorly understood. We found that WHIRLY1 interacts with Histone Deacetylase (HDA)15, a Reduced Potassium Dependence3 (RPD3)/HDA1-type HDA, by using green fluorescent protein-nanotrap-mass spectrum assays. The development-dependent interaction between WHIRLY1 and HDA15 was further confirmed by bimolecular fluorescence complementation assays and co-immunoprecipitation assays in Arabidopsis. Multi-omics genome-wide transcriptome and H3K9 acetylome enrichment analysis showed that HDA15 delays leaf senescence and flowering by repressing the expression of the positive regulators of leaf senescence and flowering, such as LOX2 and LARP1C, and reducing H3K9ac levels at these loci; WHIRLY1 and HDA15 co-target to the region near the transcription start site of a subset of nutrient recycling-related genes (e.g., Glutathione S-transferases 10, non-coding RNA, and photosystem II protein D1 synthesizer attenuator PDIL1-2), as well as WRKY53 and ELF4, and co-repress their expression by removing H3K9 acetylation. Our study revealed a key transcription regulatory node of nutrient recycling and senescence-associated genes involved in leaf senescence and flowering via the recruitment of HDA15 by the single-stranded DNA/RNA-binding protein WHIRLY1.

BZIP71 delays flowering by suppressing Ehd1 expression in rice.

Flowering time is a fundamental factor determining the global distribution and final yield of rice (Oryza sativa). Although diverse flowering time genes have been reported in this crop, the transcriptional regulation of its key flowering genes are poorly understood. Here, we report that a basic leucine zipper transcription factor, bZIP71, functions as a flowering repressor. The overexpression of bZIP71 delays flowering, while the bzip71 mutant flowers early in both long-day and short-day conditions. A genetic analysis showed that the regulation of flowering by bZIP71 might be independent of Heading date 2 (Hd2), Hd4, and Hd5. Importantly, bZIP71 directly associates with the Early heading date 1 (Ehd1) promoter and represses its transcription, and genetically the function of bZIP71 is impaired in the ehd1 mutant. Moreover, bZIP71 interacts with major components of polycomb repressive complex 2 (PRC2), SET domain group protein 711 (SDG711), and Fertilization independent endosperm 2 (FIE2), through which bZIP71 regulates the H3K27me3 level of Ehd1. Taken together, we present a transcriptional regulatory mechanism in which bZIP71 enhances the H3K27me3 level of Ehd1 and transcriptionally represses its expression, which not only offers a novel insight into a flowering pathway, but also provides a valuable putative target for the genetic engineering and breeding of elite rice cultivars.

DNA Demethylation Induces Tree Peony Flowering with a Low Deformity Rate Compared to Gibberellin by Inducing PsFT Expression under Forcing Culture Conditions.

Gibberellin (GA) is frequently used in tree peony forcing culture, but inappropriate application often causes flower deformity. Here, 5-azacytidine (5-azaC), an efficient DNA demethylating reagent, induced tree peony flowering with a low deformity rate by rapidly inducing PsFT expression, whereas GA treatment affected various flowering pathway genes with strong pleiotropy. The 5-azaC treatment, but not GA, significantly reduced the methylation level in the PsFT promoter with the demethylation of five CG contexts in a 369 bp CG-rich region, and eight light-responsive related cis-elements were also predicted in this region, accompanied by enhanced leaf photosynthetic efficiency. Through GO analysis, all methylation-closer differentially expressed genes (DEGs) were located in the thylakoid, the main site for photosynthesis, and were mainly involved in response to stimulus and single-organism process, whereas GA-closer DEGs had a wider distribution inside and outside of cells, associated with 12 categories of processes and regulations. We further mapped five candidate DEGs with potential flowering regulation, including three kinases (SnRK1, WAK2, and 5PTase7) and two bioactive enzymes (cytochrome P450 and SBH1). In summary, 5-azaC and GA may have individual roles in inducing tree peony flowering, and 5-azaC could be a preferable regulation approach; DNA demethylation is suggested to be more focused on flowering regulation with PsFT playing a core role through promoter demethylation. In addition, 5-azaC may partially undertake or replace the light-signal function, combined with other factors, such as SnRK1, in regulating flowering. This work provides new ideas for improving tree peony forcing culture technology.

Mutation of an Essential 60S Ribosome Assembly Factor MIDASIN 1 Induces Early Flowering in Arabidopsis.

Ribosome biogenesis is tightly associated with plant growth and reproduction. Mutations in genes encoding ribosomal proteins (RPs) or ribosome biogenesis factors (RBFs) generally result in retarded growth and delayed flowering. However, the early-flowering phenotype resulting from the ribosome biogenesis defect is rarely reported. We previously identified that the AAA-ATPase MIDASIN 1 (MDN1) functions as a 60S RBF in Arabidopsis. Here, we found that its weak mutant mdn1-1 is early-flowering. Transcriptomic analysis showed that the expression of FLOWERING LOCUS C (FLC) is down-regulated, while that of some autonomous pathway genes and ABSCISIC ACID-INSENSITIVE 5 (ABI5) is up-regulated in mdn1-1. Phenotypic analysis revealed that the flowering time of mdn1-1 is severely delayed by increasing FLC expression, suggesting that the early flowering in mdn1-1 is likely associated with the downregulation of FLC. We also found that the photoperiod pathway downstream of CONSTANTS (CO) and FLOWERING LOCUS T (FT) might contribute to the early flowering in mdn1-1. Intriguingly, the abi5-4 allele completely blocks the early flowering in mdn1-1. Collectively, our results indicate that the ribosome biogenesis defect elicited by the mutation of MDN1 leads to early flowering by affecting multiple flowering regulation pathways.

Temporal transcriptome analysis provides molecular insights into flower development in red-flesh pitaya

BackgroundPitaya is an important economic fruit worldwide due to its numerous health benefits. A systematic understanding of the mechanism underlying flower development is essential to obtain higher fruit yield and quality. However, the genetic mechanism of flower development is not yet investigated in pitaya. Herein, a transcriptome analysis was performed to determine the transcriptional changes during flower development in red-flesh pitaya by utilizing nine different stages of flower development. ResultA total of 95,412 unigenes were generated with a mean length of 913 nt, and N50 value of 1878 nt. Comparative transcriptomic analysis showed many differentially expressed genes (DEGs) among the flower growth stages. Furthermore, an array of key DEGs were enriched in hormone signaling, transcription, carbohydrate transport, and energy production pathways. In particular, indole-3-acetic acid, abscisic acid, ethylene-responsive transcription factor, constans-like, teosinte branched 1/cycloidea/proliferating cell nuclear antigen factor, apetala1-like, agamous-like MADS-box protein, sepallata, growth-regulating factor, putative axial regulator yabby, leafy/floricaula homolog, and MYB gene-associated transcription factors displayed altered expression, suggesting their critical roles in floral organ development of pitaya. Besides, genes related to sugar synthesis, transportation, and utilization mediate flower growth regulation in pitaya. Eleven genes were selected to perform qRT-PCR analysis to verify the results of the RNA sequencing. ConclusionsOur results provide important insights into the transcriptional regulation of pitaya flower development. These data resources will be a cornerstone for future research that aims at exploring the genetic control of flower development in pitaya.How to cite: Wu Z, Huang L, Huang F, et al. Temporal transcriptome analysis provides molecular insights into flower development in red-flesh pitaya. Electron J Biotechnol 2022;58 https://doi.org/10.1016/j.ejbt.2022.05.005

FLOWERING LOCUS T paralogs control the annual growth cycle in Populus trees

In temperate and boreal regions, perennials adapt their annual growth cycle to the change of seasons. These adaptations ensure survival in harsh environmental conditions, allowing growth at different latitudes and altitudes, and are therefore tightly regulated. Populus tree species cease growth and form terminal buds in autumn when photoperiod falls below a certain threshold.1 This is followed by establishment of dormancy and cold hardiness over the winter. At the center of the photoperiodic pathway in Populus is the gene FLOWERING LOCUS T2 (FT2), which is expressed during summer and harbors significant SNPs in its locus associated with timing of bud set.1-4 The paralogous gene FT1, on the other hand, is hyper-induced in chilling buds during winter.3,5 Even though its function is so far unknown, it has been suggested to be involved in the regulation of flowering and the release of winter dormancy.3,5 In this study, we employ CRISPR-Cas9-mediated gene editing to individually study the function of the FT-like genes in Populus trees. We show that while FT2 is required for vegetative growth during spring and summer and regulates the entry into dormancy, expression of FT1 is absolutely required for bud flush in spring. Gene expression profiling suggests that this function of FT1 is linked to the release of winter dormancy rather than to the regulation of bud flush per se. These data show how FT duplication and sub-functionalization have allowed Populus trees to regulate two completely different and major developmental control points during the yearly growth cycle.

Genome-Wide Analysis of the MADS-Box Gene Family in Holoparasitic Plants (Balanophora subcupularis and Balanophora fungosa var. globosa).

MADS-box is an important transcription factor family that is involved in the regulation of various stages of plant growth and development, especially flowering regulation and flower development. Being a holoparasitic plant, the body structure of Balanophoraceae has changed dramatically over time, and its vegetative and reproductive organs have been extensively modified, with rudimentary flower organs. Meanwhile, extraordinary gene losses have been identified in holoparasitic plants compared with autotrophs. Our study reveals that the MADS-box gene family contracted sharply in Balanophora subcupularis and Balanophora fungosa var. globosa, and some subfamilies were lost, exhibiting reduced redundancy in both. The genes that functioned in the transition from the vegetative to floral production stages suffered a significant loss, but the ABCE model genes remained intact. We further investigated genes related to flowering regulation in B. subcupularis and B. fungosa var. globosa, vernalization and autonomous ways of regulating flowering time remained comparatively integrated, while genes in photoperiod and circadian clock pathways were almost lost. Convergent gene loss in flowering regulation occurred in Balanophora and another holoparasitic plant Sapria himalayana (Rafflesiaceae). The genome-wide analysis of the MADS-box gene family in Balanophora species provides valuable information for understanding the classification, gene loss pattern, and flowering regulation mechanism of MADS-box gene family in parasitic plants.

Genome-Wide Identification, Classification, Expression and Duplication Analysis of bZIP Family Genes in Juglans regia L.

Basic leucine zipper (bZIP), a conserved transcription factor widely found in eukaryotes, has important regulatory roles in plant growth. To understand the information related to the bZIP gene family in walnut, 88 JrbZIP genes were identified at the genome-wide level and classified into 13 subfamilies (A, B, C, D, E, F, G, H, I, J, K, M, and S) using a bioinformatic approach. The number of exons in JrbZIPs ranged from 1 to 12, the number of amino acids in JrbZIP proteins ranged from 145 to 783, and the isoelectric point ranged from 4.85 to 10.05. The majority of JrbZIP genes were localized in the nucleus. The promoter prediction results indicated that the walnut bZIP gene contains a large number of light-responsive and jasmonate-responsive action elements. The 88 JrbZIP genes were involved in DNA binding and nucleus and RNA biosynthetic processes of three ontological categories, molecular functions, cellular components and biological processes. The codon preference analysis showed that the bZIP gene family has a stronger bias for AGA, AGG, UUG, GCU, GUU, and UCU than other codons. Moreover, the transcriptomic data showed that JrbZIP genes might play an important role in floral bud differentiation. The results of a protein interaction network map and kegg enrichment analysis indicated that bZIP genes were mainly involved in phytohormone signaling, anthocyanin synthesis and flowering regulation. qRT-PCR demonstrated the role of the bZIP gene family in floral bud differentiation. Co-expression network maps were constructed for 29 walnut bZIP genes and 6 flowering genes, and JrCO (a homolog of AtCO) was significantly correlated (p < 0.05) with 13 JrbZIP genes in the level of floral bud differentiation expression, including JrbZIP31 (homolog of AtFD), and JrLFY was significantly and positively correlated with JrbZIP10,11,51,59,67 (p < 0.05), and the above results suggest that bZIP family genes may act together with flowering genes to regulate flower bud differentiation in walnut. This study was the first genome-wide report of the walnut bZIP gene family, which could improve our understanding of walnut bZIP proteins and provide a solid foundation for future cloning and functional analyses of this gene family.

Autophagy targets Hd1 for vacuolar degradation to regulate rice flowering

Flowering time (heading date) is a critical agronomic trait that determines the yield and regional adaptability of crops. Heading date 1 (Hd1) is a central regulator of photoperiodic flowering in rice (Oryza sativa). However, how the homeostasis of Hd1 protein is achieved is poorly understood. Here, we report that the nuclear autophagy pathway mediates Hd1 degradation in the dark to regulate flowering. Loss of autophagy function results in an accumulation of Hd1 and delays flowering under both short-day and long-day conditions. In the dark, nucleus-localized Hd1 is recognized as a substrate for autophagy and is subjected to vacuolar degradation via the autophagy protein OsATG8. The Hd1-OsATG8 interaction is required for autophagic degradation of Hd1 in the dark. Our study reveals a new mechanism by which Hd1 protein homeostasis is regulated by autophagy to control rice flowering. Our study also indicates that the regulation of flowering by autophagic degradation of Hd1 orthologs may have arisen over the course of mesangiosperm evolution, which would have increased their flexibility and adaptability to the environment by modulating flowering time.

Genome-Wide Identification, Characterization, and Expression Profiling Analysis of SPL Gene Family during the Inflorescence Development in Trifolium repens.

Trifolium repens is the most widely cultivated perennial legume forage in temperate region around the world. It has rich nutritional value and good palatability, seasonal complementarity with grasses, and can improve the feed intake and digestibility of livestock. However, flowering time and inflorescence development directly affects the quality and yield of T. repens, as well as seed production. The Squa promoter binding protein-like (SPL) gene family is a plant specific transcription factor family, which has been proved to play a critical role in regulating plant formation time and development of flowers. In this study, a total of 37 TrSPL genes were identified from the whole genome of T. repens and were divided into nine clades based on phylogenetic tree. Seventeen TrSPL genes have potential target sites for miR156. The conserved motif of squamosa promoter binding protein (SBP) contains two zinc finger structures and one NLS structure. Gene structure analysis showed that all TrSPL genes contained SBP domain, while ankyrin repeat region was just distributed in part of genes. 37 TrSPL genes were relatively dispersedly distributed on 16 chromosomes, and 5 pairs of segmental repeat genes were found, which indicated that segmental duplication was the main way of gene expansion. Furthermore, the gene expression profiling showed that TrSPL11, TrSPL13, TrSPL22, and TrSPL26 were highly expressed only in the early stage of inflorescence development, while TrSPL1 and TrSPL6 are highly expressed only in the mature inflorescence. Significantly, the expression of TrSPL4 and TrSPL12 increased gradually with the development of inflorescences. The results of this study will provide valuable clues for candidate gene selection and elucidating the molecular mechanism of T. repens flowering regulation.

Identification of Flowering Regulatory Networks and Hub Genes Expressed in the Leaves of Elymus sibiricus L. Using Comparative Transcriptome Analysis.

Flowering is a significant stage from vegetative growth to reproductive growth in higher plants, which impacts the biomass and seed yield. To reveal the flowering time variations and identify the flowering regulatory networks and hub genes in Elymus sibiricus, we measured the booting, heading, and flowering times of 66 E. sibiricus accessions. The booting, heading, and flowering times varied from 136 to 188, 142 to 194, and 148 to 201 days, respectively. The difference in flowering time between the earliest- and the last-flowering accessions was 53 days. Furthermore, transcriptome analyses were performed at the three developmental stages of six accessions with contrasting flowering times. A total of 3,526 differentially expressed genes (DEGs) were predicted and 72 candidate genes were identified, including transcription factors, known flowering genes, and plant hormone-related genes. Among them, four candidate genes (LATE, GA2OX6, FAR3, and MFT1) were significantly upregulated in late-flowering accessions. LIMYB, PEX19, GWD3, BOR7, PMEI28, LRR, and AIRP2 were identified as hub genes in the turquoise and blue modules which were related to the development time of flowering by weighted gene co-expression network analysis (WGCNA). A single-nucleotide polymorphism (SNP) of LIMYB found by multiple sequence alignment may cause late flowering. The expression pattern of flowering candidate genes was verified in eight flowering promoters (CRY, COL, FPF1, Hd3, GID1, FLK, VIN3, and FPA) and four flowering suppressors (CCA1, ELF3, Ghd7, and COL4) under drought and salt stress by qRT-PCR. The results suggested that drought and salt stress activated the flowering regulation pathways to some extent. The findings of the present study lay a foundation for the functional verification of flowering genes and breeding of new varieties of early- and late-flowering E. sibiricus.

Bud Induction and Observation of In Vitro Flowering from the Callus of Ananas bracteatus var. tricolor

In natural conditions, it takes more than 3 years to complete the Ananas juvenile phase, and another 2 years for adult vegetative growth of the plantlet from in vitro buds. Ethylene has often been used to shorten the juvenile and vegetative phases to produce earlier flowering. It is important to induce in vitro flowering of Ananas plants to understand the flowering mechanism more completely, which is also related to flower organ differentiation and development as well as the pineapple fruit eye development. In this study, Murashige and Skoog (MS) basal medium was used to select the best combination for adventitious bud induction from the callus of Ananas bracteatus var. tricolor (A. tricolor). Flower induction from the callus was studied using 6-benzyladenine (6-BA) and 1-naphthylacetic acid (NAA) at four different concentrations (0, 1.0, 2.0, and 3.0 mg⋅L–1). Our results showed that when MS was added with 3 mg⋅L–1 6-BA and 2 mg⋅L–1 NAA under 2000 μmol⋅m–2⋅s–1 of light for 16 hours per day at a temperature of 20 °C, the callus of A. tricolor grew quickly, and adventitious buds were induced. After more than four successive subcultures (at day 80), differentiation of flower buds was observed on the aging callus tissue before a complete floral organ developed. This research could be used for the flowering regulation of Ananas plants in the future. Inducing flowers directly from the callus has important scientific significance for the differentiation and morphogenesis of Ananas plants.

Molecular mechanisms and evolutionary history of phytomelatonin in flowering

Flowering is a critical stage in plant life history, which is coordinated by environmental signals and endogenous cues. Phytomelatonin is a widely distributed indoleamine present in all living organisms and plays pleiotropic roles in plant growth and development. Recent evidence has established that phytomelatonin could modulate flowering in many species, probably in a concentration-dependent manner. Phytomelatonin seems to associate with floral meristem identification and floral organ formation, and the fluctuation of phytomelatonin might be important for flowering. Regarding the underlying mechanisms, phytomelatonin interacts with the central components of floral gene regulatory networks directly or indirectly, including the MADS-box gene family, phytohormones, and reactive oxygen species (ROS). From an evolutionary point of view, the actions of phytomelatonin in flowering probably evolved during the period of the diversification of flowering plants and could be regarded as a functional extension of its primary activities. The presumed evolutionary history of phytomelatonin-modulated flowering is proposed, presented in the chronological order of the appearance of phytomelatonin and core flowering regulators, namely DELLA proteins, ROS, and phytohormones. Further efforts are needed to address some intriguing aspects, such as the exploration of the association between phytomelatonin and photoperiodic flowering, phytomelatonin-related floral MADS-box genes, the crosstalk between phytomelatonin and phytohormones, as well as its potential applications in agriculture.

Why Black Flowers? An Extreme Environment and Molecular Perspective of Black Color Accumulation in the Ornamental and Food Crops.

Pollinators are attracted to vibrant flower colors. That is why flower color is the key agent to allow successful fruit set in food or ornamental crops. However, black flower color is the least attractive to pollinators, although a number of plant species produce black flowers. Cyanidin-based anthocyanins are thought to be the key agents to induce black color in the ornamental and fruit crops. R2R3-MYB transcription factors (TFs) play key roles for the tissue-specific accumulation of anthocyanin. MYB1 and MYB11 are the key TFs regulating the expression of anthocyanin biosynthesis genes for black color accumulation. Post-transcriptional silencing of flavone synthase II (FNS) gene is the technological method to stimulate the accumulation of cyanidin-based anthocyanins in black cultivars. Type 1 promoter of DvIVS takes the advantage of FNS silencing to produce large amounts of black anthocyanins. Exogenous ethylene application triggers anthocyanin accumulation in the fruit skin at ripening. Environment cues have been the pivotal regulators to allow differential accumulation of anthocyanins to regulate black color. Heat stress is one of the most important environmental stimulus that regulates concentration gradient of anthocyanins in various plant parts, thereby affecting the color pattern of flowers. Stability of black anthocyanins in the extreme environments can save the damage, especially in fruits, caused by abiotic stress. White flowers without anthocyanin face more damages from abiotic stress than dark color flowers. The intensity and pattern of flower color accumulation determine the overall fruit set, thereby controlling crop yield and human food needs. This review paper presents comprehensive knowledge of black flower regulation as affected by high temperature stress, and the molecular regulators of anthocyanin for black color in ornamental and food crops. It also discusses the black color-pollination interaction pattern affected by heat stress for food and ornamental crops.

Screening and Functional Verification of Vernalization-Related Genes in Chinese Cabbage

Flowering is very important for leaf head formation and breeding. Investigating the key genes related to vernalization process can reveal the flowering regulation mechanism and guide production and germplasm breeding. In this study, two Chinese cabbage (Brassica rapa subsp. pekinensis) inbred lines ‘1#’ and ‘2#’ with different winterness were used to identify vernalization-related genes. After low-temperature treatment, the transcriptomes of the shoot apex of the two lines were analyzed. The Arabidopsis thaliana homologues of 2,932 common differentially expressed genes with the same change trend after vernalization of two inbred lines were analysed based on Gene Ontology annotation and description. The results showed that, three genes were identified that may be related to the vernalization: Bra031210, Bra009126 and Bra033615. In which Bra031210 and Bra009126 were cloned, named BrGRP7.1 and BrCPD1, with open reading frames lengths of 507 and 1443 bp, encoding 168 and 480 amino acids, respectively. Through the expression patterns analysis, the expression of BrGRP7.1 showed a trend of initial decreasing (dipping at stage 1) and then increasing (peaking at stage 5) during flower bud differentiation of both inbred lines. Incontrast, BrCPD1 showed a first decreasing, then increasing, and last decreasing trend during flower bud differentiation of both lines. These two genes were transferred into wild-type A. thaliana. The flowering time of T2 generation of BrGRP7.1- and BrCPD1-transgenic plants was 2.31~5.11 days and 2.64~4.35 days earlier than the wild-type, respectively. In conclusion, this study screened three genes that involved in the vernalization process. Through functional verification, BrGRP7.1 and BrCPD1 were proved to have the ability to promote flowering time. This study provided a reference for further study on the flowering mechanism of Chinese cabbage.