Vernalization Conditions Research Articles

Chromatin loops gather targets of upstream regulators together for efficient gene transcription regulation during vernalization in wheat

BackgroundPlants respond to environmental stimuli by altering gene transcription that is highly related with chromatin status, including histone modification, chromatin accessibility, and three-dimensional chromatin interaction. Vernalization is essential for the transition to reproductive growth for winter wheat. How wheat reshapes its chromatin features, especially chromatin interaction during vernalization, remains unknown.ResultsCombinatory analysis of gene transcription and histone modifications in winter wheat under different vernalization conditions identifies 17,669 differential expressed genes and thousands of differentially enriched peaks of H3K4me3, H3K27me3, and H3K9ac. We find dynamic gene expression across the vernalization process is highly associated with H3K4me3. More importantly, the dynamic H3K4me3- and H3K9ac-associated chromatin-chromatin interactions demonstrate that vernalization leads to increased chromatin interactions and gene activation. Remarkably, spatially distant targets of master regulators like VRN1 and VRT2 are gathered together by chromatin loops to achieve efficient transcription regulation, which is designated as a “shepherd” model. Furthermore, by integrating gene regulatory network for vernalization and natural variation of flowering time, TaZNF10 is identified as a negative regulator for vernalization-related flowering time in wheat.ConclusionsWe reveal dynamic gene transcription network during vernalization and find that the spatially distant genes can be recruited together via chromatin loops associated with active histone mark thus to be more efficiently found and bound by upstream regulator. It provides new insights into understanding vernalization and response to environmental stimuli in wheat and other plants.

Floral scents, specialized metabolites and stress-response activities in Heritiera fomes and Bruguiera gymnorrhiza from Sundarban mangrove ecosystem.

Floral biochemistry and stress physiology is an underexplored aspect of mangroves, which should be investigated as part of preservation and restoration efforts. A thriving true mangrove tree (Bruguiera gymnorrhiza (L.) Lamk.) and a threatened mangrove-associate species (Heritiera fomes Buch. Ham.) were studied in the Sundarban region of India for seasonal variations in floral odours, non-volatile phytochemicals, antioxidant enzyme activities, and surface water chemistry in surrounding habitat. Both species were found to exhibit significant differences in floral volatilomes, protein contents, antioxidant enzyme activities, total flavonoids, and total phenolic contents between spring and autumn blooms. The bird-pollinated flowers of B. gymnorrhiza also showed considerable seasonal differences in floral anthocyanin and proline contents, indicating vulnerability of the post-anthesis open flowers to environmental factors. Contrarily to previous findings, B. gymnorrhiza floral bouquet appeared to be enriched in various classes of volatiles - dominated by sulphurous compounds in bud stage and terpenoids in open stage. Floral anthocyanins, contributing to the striking colouration of the calyx, were found to comprise cyanidin and delphinidin derivatives. Other glycosides of cyanidin and delphinidin were detected in H. fomes flowers, contributing to visual guides to potential food rewards for pollinating insects. Floral tissue in H. fomes was found to be protected by densely overlapping layers of stellate trichomes containing sesquiterpenoids as phytoprotectants. Comparison of the two floral species suggested that H. fomes flowering is optimized to oligohaline (but not freshwater) vernal conditions; whereas B. gymnorrhiza blooms are adapted for biologically enriched (including abundant herbivores and microbial growth), mesohaline forest habitats.

Natural variations of wheat EARLY FLOWERING 3 highlight their contributions to local adaptation through fine-tuning of heading time

We identified a large chromosomal deletion containing TaELF-B3 that confers early flowering in wheat. This allele has been preferred in recent wheat breeding in Japan to adapt to the environment. Heading at the appropriate time in each cultivation region can greatly contribute to stabilizing and maximizing yield. Vrn-1 and Ppd-1 are known as the major genes for vernalization requirement and photoperiod sensitivity in wheat. Genotype combinations of Vrn-1 and Ppd-1 can explain the variation in heading time. However, the genes that can explain the remaining variations in heading time are largely unknown. In this study, we aimed to identify the genes conferring early heading using doubled haploid lines derived from Japanese wheat varieties. Quantitative trait locus (QTL) analysis revealed a significant QTL on the long arm of chromosome 1B in multiple growing seasons. Genome sequencing using Illumina short reads and Pacbio HiFi reads revealed a large deletion of a ~ 500kb region containing TaELF-B3, an orthologue of Arabidopsis clock gene EARLY FLOWERING 3 (ELF3). Plants with the deleted allele of TaELF-B3 (ΔTaELF-B3 allele) headed earlier only under short-day vernalization conditions. Higher expression levels of clock- and clock-output genes, such as Ppd-1 and TaGI, were observed in plants with the ΔTaELF-B3 allele. These results suggest that the deletion of TaELF-B3 causes early heading. Of the TaELF-3 homoeoalleles conferring early heading, the ΔTaELF-B3 allele showed the greatest effect on the early heading phenotype in Japan. The higher allele frequency of the ΔTaELF-B3 allele in western Japan suggests that the ΔTaELF-B3 allele was preferred during recent breeding to adapt to the environment. TaELF-3 homoeologs will help to expand the cultivated area by fine-tuning the optimal timing of heading in each environment.

Epistatic interactions among multiple copies of FLC genes with naturally occurring insertions correlate with flowering time variation in radish.

Brassicaceae crops, which underwent whole-genome triplication during their evolution, have multiple copies of flowering-related genes. Interactions among multiple gene copies may be involved in flowering time regulation; however, this mechanism is poorly understood. In this study, we performed comprehensive, high-throughput RNA sequencing analysis to identify candidate genes involved in the extremely late-bolting (LB) trait in radish. Then, we examined the regulatory roles and interactions of radish FLOWERING LOCUS C (RsFLC) paralogs, the main flowering repressor candidates. Seven flowering integrator genes, five vernalization genes, nine photoperiodic/circadian clock genes and eight genes from other flowering pathways were differentially expressed in the early-bolting (EB) cultivar 'Aokubinagafuto' and LB radish cultivar 'Tokinashi' under different vernalization conditions. In the LB cultivar, RsFLC1 and RsFLC2 expression levels were maintained after 40 days of cold exposure. Bolting time was significantly correlated with the expression rates of RsFLC1 and RsFLC2. Using the EB × LB F2 population, we performed association analyses of genotypes with or without 1910- and 1627-bp insertions in the first introns of RsFLC1 and RsFLC2, respectively. The insertion alleles prevented the repression of their respective FLC genes under cold conditions. Interestingly, genotypes homozygous for RsFLC2 insertion alleles maintained high RsFLC1 and RsFLC3 expression levels under cold conditions, and two-way analysis of variance revealed that RsFLC1 and RsFLC3 expression was influenced by the RsFLC2 genotype. Our results indicate that insertions in the first introns of RsFLC1 and RsFLC2 contribute to the late-flowering trait in radish via different mechanisms. The RsFLC2 insertion allele conferred a strong delay in bolting by inhibiting the repression of all three RsFLC genes, suggesting that radish flowering time is determined by epistatic interactions among multiple FLC gene copies.

BraVRG, a novel protein of Brassica rapa, is induced by vernalization and promotes flowering in Arabidopsis thaliana

Plant flowering is an important economical characteristic for the transformation from vegetative growth to reproductive growth, especially for biennial crops. Additionally, bolting or flowering time is more important for vegetable plants due to their different harvest organs, such as flower for cauliflower and broccoli and leafy heads for cabbage and Chinese cabbage. The flowering time of Arabidopsis thaliana has six classical regulated pathways, and some key regulated genes are identified in Brassicaceae crops. However, the regulatory mechanism needs further exploration. Here, we reported an novel protein BraVRG (Vernalization Related Gene) of Chinese cabbage induced by vernalization. The expression of BraVRG increased rapidly at 14 day of vernalization in the semi-winter type of Brassica rapa and 21 days for the winter types. Meanwhile the modifications of H3K4me3 deposited on BraVRG increased but H3K27me3 decreased. Moreover, BraVRG promoted flowering in transgenic A. thaliana compared with the wild types accompanied the downregulated expression of FLC caused by the decrease of H3K4me3 enrichment and the increase of H3K27me3 on FLC with or without vernalization conditions.

Depicting Precise Temperature and Duration of Vernalization and Inhibiting Early Bolting and Flowering of Angelica sinensis by Freezing Storage.

Angelica sinensis is a perennial rhizomatous herb that is widely used for the treatment of cardio-cerebrovascular diseases, which largely rely on metabolites, such as alkylphthalides, polysaccharides, and ferulic acid. This plant must experience low-temperature vernalization and long-day conditions for the occurrence of early bolting and flowering (EBF) that reduces yield and quality of fleshy root. In current commercial planting, the EBF of more than 40% is mainly attributed to the completion of vernalization of seedlings during overwinter storage. While effects of storage temperatures [vernalization temperature (0–10°C) and freezing temperature (−2 to −12°C)] and seedling sizes on the EBF have been observed in previous studies, the precise vernalization temperature and duration for different size seedlings, the effective freezing storage to avoid vernalization of seedlings, and physiological characteristics have not been systematically investigated. Here, the EBF rate, the anatomical structure of shoot apical meristem (SAM), and physiological characteristics of different size seedlings at different storage temperatures (0, 3, 5, −3, and −5°C) and durations (14–125 d) are reported. The vernalization duration of seedlings was predicated from 57 to 85 d with temperatures ranging from 0 to 5°C based on the linearization regression analysis via Matrix Laboratory software. The EBF can be effectively inhibited by freezing storage. The anatomical structure of SAM, levels of primary metabolites (soluble sugar, starch, amino acid, and protein), and endogenous hormones (GA3, IAA, and ABA), exhibited a dynamical change in the seedlings at different storage temperatures. These findings will provide useful information for predicting the vernalization of seedlings and inhibiting the EBF in large-scale commercial cultivation.

Seed production potential evaluation of sugar beet half-sib families in Morocco

AbstractIn Morocco, sugar-beet seed production represents a new challenge to meet the main breeding programme goals. The identification of a suitable zone for plant vernalization represents a bottleneck for seed production. This study aimed chiefly at evaluating the vernalization aptitude of 18 sugar beet half-sib progenies. Trials were conducted during three selection cycles in a specifically chosen environment. The experimental site of Merchouch is 40 km south-east of Rabat city. Field trials design is according to an open-pollinated experimental block. Yield components and five phenological traits were recorded during the growing cycle and at the plant maturation. The variance analysis showed a significant effect of the selection cycle on the phenological traits and grain yield. The plant cycle duration increased by 10.7 days between the first and the third selection cycles. According to the principal component analysis and the hierarchical clustering, F2, F5, F6, F9, F10, F11, F14 and F15 half-sib progenies are described as long cycle and high grain yield families. Grain yield reached 257.3 g per plant, the duration to maturity 350.6 days and the germination rate 93%. The three selection cycles and the suitability of the site vernalization conditions are potentially effective for seed production progress. Our results are relevant as they established an adequate site for the sugar beet seed production. The half-sib selection is a valuable method for sugar beet germplasm enhancement.

Kernza intermediate wheatgrass (Thinopyrum intermedium) response to a range of vernalization conditions

Expansion of perennial grain and forage Kernza intermediate wheatgrass to temperate regions may be limited by its vernalization requirements. We compared vegetative and reproductive traits of Kernza plants grown in the greenhouse under four environmental treatments of temperature and day length for a 7 week induction period. The percent of plants that flowered and spikes per plant decreased from 83% and 8.2 at 4 °C and 10 h to 15% and 0.4 at 26 °C and 15 h, respectively. The variability observed suggests that there is potential for selection for reduced vernalization requirements in Kernza populations.

Functional characterization of wheat histone H2B monoubiquitination enzyme TaHUB2 in response to vernalization in Keumkang (Triticum aestivum L.)

ABSTRACT Histone monoubiquitination has an important role in the regulation of DNA replication, repair, and transcription in plants. Here, we report the molecular function of wheat histone H2B monoubiquitination enzyme 2 (TaHUB2). The full length of TaHUB2 contains a Really Interesting New Gene (RING) domain and its encoded protein was localized in both nucleus and cytoplasm. We also find TaHUB2 directly interacts with histone H2B in yeast and tobacco. The transcription level of TaHUB2 was decreased as the increased vernalization periods until 50 d. The TaHUB2 exhibited ubiquitination activities and were rapidly degraded in the cell-free extracts with apparently 3–6 h after vernalization compared with non-vernalization. Moreover, histone H2B was mono-ubiquitinated by TaHUB2 and ubiquitylated histone H2B (H2Bub1) level was decreased after vernalization conditions in wheat. These results provide novel information for understanding the molecular characterization of wheat RING-type E3 ligase and their possible roles.

Development of an Effective In Vitro Regeneration System for Ukrainian Breeding Winter Rape Brassica napus L.

An optimized regeneration method for commercial winter rape of the Bn1 line was proposed. Hypocotyl fragments of 6-day-old seedlings were used as explants. Regeneration occurred via organogenesis on an MS medium supplemented with 3 mg/L of 6-benzylaminopurine and 2 mg/L of 2-isopentyladenine. All obtained regenerated plants successfully formed roots on hormone-free media and were adapted to the soil conditions. The vernalization conditions were specified to promote budding and flowering at the level of 83.93 ± 5.33%. The PCR analysis using the ISSR 2 and ISSR 15 markers has shown that no somaclonal variations in Bn1 winter rape occur under the protocols based on the proposed methodology. Thus, the developed methodology is efficient and economically profitable for obtaining biotechnology-based winter rape plants.

Gibberellin Promotes Bolting and Flowering via the Floral Integrators RsFT and RsSOC1-1 under Marginal Vernalization in Radish.

Gibberellic acid (GA) is one of the factors that promotes flowering in radish (Raphanus Sativus L.), although the mechanism mediating GA activation of flowering has not been determined. To identify this mechanism in radish, we compared the effects of GA treatment on late-flowering (NH-JS1) and early-flowering (NH-JS2) radish lines. GA treatment promoted flowering in both lines, but not without vernalization. NH-JS2 plants displayed greater bolting and flowering pathway responses to GA treatment than NH-JS1. This variation was not due to differences in GA sensitivity in the two lines. We performed RNA-seq analysis to investigate GA-mediated changes in gene expression profiles in the two radish lines. We identified 313 upregulated, differentially expressed genes (DEGs) and 207 downregulated DEGs in NH-JS2 relative to NH-JS1 in response to GA. Of these, 21 and 8 genes were identified as flowering time and GA-responsive genes, respectively. The results of RNA-seq and quantitative PCR (qPCR) analyses indicated that RsFT and RsSOC1-1 expression levels increased after GA treatment in NH-JS2 plants but not in NH-JS1. These results identified the molecular mechanism underlying differences in the flowering-time genes of NH-JS1 and NH-JS2 after GA treatment under insufficient vernalization conditions.

THE LINE RICO IS THE EARLIEST MATURING ACCESSION IN THE VIR COLLECTION OF SPRING BREAD WHEAT

Background. To optimize the process of bread wheat breeding for earliness and environmental adaptability, searching for new source material is a crucial task. The ultra-early line Rico (k-65588) – Triticum aestivum var. erythrospermum Koern. – stands out among the bread wheat accessions from the VIR collection for its important adaptive features.Materials and methods. Spring wheat accessions with different speed of development were selected from the VIR collection for this study, along with the ultra-early lines Rifor 1 ... 10 (F6-7 Rico × Forlani Roberto k-42641) and Fori 1 ... 8 (k-65589 ... k-65596) (F4 Foton k-55696 × Rico). Their responses to a short 12-hour day were assessed. Vernalization conditions were 30 days at 3°C. The genetics of plant sensitivity to vernalization and photoperiods was studied using allele-specific primers for the genes Vrn-A1, Vrn-B1, Vrn-D1 and Ppd-D1.Results and conclusions. In the Northwest of Russia, the period from seeding to heading for Rico plants was 39.9 ± 1.49 days, or 14.8 ± 1.22 days less than for the released commercial wheat cultivars. Among the 8400 wheat accessions, studied by the Wheat Genetic Resources Department of VIR in this area from 1948 to 2018, the shortest period from germination to heading was observed in the line Rico: 29 (28–30) days. The absence of response to vernalization in Rico, Fori and Rifor lines was determined by the dominant alleles Vrn-A1, Vrn-B1 and Vrn-D1. Photoperiodism in Rico and partially in Rifor was controlled by at least two genes: Ppd-D1 and Ppd-B1. In the F2 population of Rico hybrids with 8 wheat accessions no transgression was observed beyond the limits of Rico‘s variation. The difference in the development rate between Rico and other wheat accessions is controlled by two or three non-allelic genes. Rifor lines can compete in productivity with commercialized wheat cultivars.

Envirotypes Based on Seed Yield Limiting Factors Allow to Tackle G × E Interactions

One challenge in plant breeding is to ensure optimized production under fluctuating environments while reducing the environmental impacts of agriculture. Thus, new rapeseed varieties should be adapted to a wide range of pedoclimatic conditions and constraints. Addressing this issue requires identifying the critical factors limiting production and the genotype by environment (G × E) interaction. Our goal was to characterize the effects of environment and G × E interaction on the seed yield of rapeseed grown over a large field network. First, we defined a pedoclimatic indicator set with the ability to highlight the potential limiting factors along the crop cycle by analyzing the yield of two genotypes grown under 20 environments. Out of the 84 pedoclimatic indicators, 10 were identified as limiting after a partial least squares regression analysis. The environments were then clustered into five envirotypes, each characterized by few major limiting factors: low winter temperatures and heat stress during seed filling (1); low solar radiation during seed filling (3); vernalization conditions during winter (4) and high temperatures at flowering (5). A larger genetic diversity was evaluated in a subset of 11 environments to analyze the impact of envirotyping on genotype ranking. Their results were discussed in light of field network management and plant breeding purposes.

Research into the influence of contrasting trophic conditions of vernalization on the allelic state of Vrn genes and development rates of Triticum aestivum L.

The influence of contrasting trophic conditions of vernalization on the allelic state of the Vrn genes and development rates of two winter wheat varieties, Mironovskaya 808 and Olvia, was investigated. Vernalization was carried out during 45 days at the temperature 4 ± 1°С under different conditions of trophic support. Whole seeds with endosperm and isolated buds, with added water and 3% solution of sucrose, were vernalized. The allelic state of the Vrn genes was identified by PCR using allele-specific primers on the sprouts at different phases of vernalization – 15, 30, and 45 days. Phenological observations were carried out by determining of the transition to the generative development of wheat plants, cultivated from the vernalized sprouts. According to the results obtained, it was established that the recessive state of the genes Vrn-A1, Vrn-B1 and Vrn-D1 was unchanged in all variants of the two winter wheat varieties on the 15th and 30th days of vernalization. After 45 days of vernalization, the recessive and dominant alleles in sprouts, vernalized under normal trophic conditions and with added 3% solution of sucrose, were detected at the Vrn-B1. All variants of wheat plants grown from vernalized sprouts under contrasting trophic conditions were transferred to the generative phase, but at different times. It could indicate an epigenetic regulation vernalization process. It was established that different trophic conditions during vernalization affected the changes of the allelic state of the Vrn-B1 gene and determined the transition to the generative development of winter wheat.

Environmental and Genetic Variation for Yield-Related Traits of Durum Wheat as Affected by Development.

Phenology has a profound effect on adaptation and productivity of crops. The impact of phenology on tillering and fertility traits of durum wheat (Triticum turgidum L. subsp. durum Desf.) was evaluated with the aim of specifying which group of flowering genes (Vrn, Ppd, or eps) was involved in their control. A recombinant inbred line population was grown under four contrasting conditions of vernalization and daylength. Phenotyping was carried out according to robust phenological models dissecting both phenological and yield related traits. Whole-genome profiling was performed using the DArT-Seq technology. The genetic variability for tillering was mainly related to the genetic variability for vernalization sensitivity, as shown by the many quantitative trait loci (QTLs) identified in non-vernalized plants associated to both tillering and phenological traits. No effects of photoperiod sensitivity on spikelet number were detected in short-day-grown plants, apparently because of limited genetic variability in photoperiod sensitivity of the population. Earliness per se was involved in control of spikelet number via final leaf number, with these traits genetically correlated and sharing some QTLs. Chaff weight and number of kernels per g chaff were negatively associated and related to anthesis date under most conditions. QTL mapping uncovered novel loci involved in phenological control of tillering and fertility traits, and confirmed the presence of several well-established loci. Phenotyping of both phenology and kernel number according to a robust physiological model amplified the possibility of identifying genetic factors underlying their variations. Also, isolating known flowering gene cues by manipulation of environmental conditions provided the opportunity for each group of genes to be expressed without confounding effects of the others. This information helps to predict the consequences of either genetic manipulation of flowering genes and changes in environmental conditions on the potential yield of durum wheat.

Effect of trophic support on the dynamics of growth processes and carbohydrate content of winter wheat sprouts under vernalization

The influence of contrasting conditions of trophic support of vernalization on the growth reaction and dynamics of the content of various fractions of soluble carbohydrates of sprouts of two winter wheat varieties Statna and Doridna were studied. In experiments, the contrasting trophic conditions of vernalization were created by adding 3% sucrose solution, as well as isolation of endosperm, a natural reserve of carbohydrates and biologically active substances. It was shown that optimal conditions of trophic support (integral seeds + water) determined the maximum linear growth and accumulation of sprouts biomass during vernalization. The excess of exogenous sugars (integral seeds + 3% sucrose solution) inhibited growth processes. However, the deficit of trophic factors (isolated buds + 3% sucrose solution) also inhibited growth and the lack of trophic support (isolated buds + water) completely inhibited growth and accumulation of sprouts biomass during 45 days of vernalization. It was established that the dynamics of changes in soluble carbohydrates content in winter wheat sprouts also depended on the trophic support level of vernalization and correlated with changes of growth reaction. It was shown the oligosaccharide content was significantly higher than monosaccharide content of sprouts of all the variants of both varieties during the entire period of vernalization. In view of the fact that monosaccharides are the most metabolically active carbohydrates, they are probably spent as much as possible at the first stages of vernalization (15–30 days). It is discussed that different level of trophic support is able to be one of the important factors of genetic and/or epigenetic regulation of Triticum aestivum L. Thus, changes in metabolic processes, in particular carbohydrate metabolism, can effect on the reduction of VRN genes expression, which are the target of epigenetic regulation, and as a result, on the ability of soft wheat plants to flower. It is assumed that the regulatory role of carbohydrates in vernalization process can be realized only at the optimal level of trophic support.

Research of influence of contrasting trophic conditions of vernalization on the mitotic activity of meristems, growth and development of winter wheat

The work is devoted to the most important physiological and selective sign of winter soft wheat Triticum aestivum L. – vernalization.Aim. The main aim of the work was the study of trophic factor influence on the effectiveness of vernalization process.Methods. In experiments were used the varieties of winter wheat – Statna and Doridna. The contrasting conditions of trophic support were created by vernalization on integral seeds (control) and isolated buds (experiment) adding water and 3-% solution of saccharose during 45 days at temperature 3±1°С. In experiments there was studied the influence of contrasting trophic conditions of vernalization on the mitotic activity of root meristems of vernalized sprouts, their growth reaction and rates of ontogenetic development of plants, cultivated from vernalized sprouts. All experiments were carried out under conditions of vegetative experiment in factorostatic chamber of the department of physiology and biochemistry of plants and microorganisms of Kharkiv national university, named after V.N. Karazin.Results. According to the results of researches, it was established that the growth reaction of sprouts at vernalization depends on their variety specific characteristics and on trophic factors presence. It was demonstrated that 3% solution of saccharose at vernalization stimulates proliferative activity of root meristems of both winter wheat varieties but doesn’t influences the parameter – duration of mitosis phases. The presence of trophic factors in sprouts at vernalization conditions the speed of phenophases passage and transfer to generative development of both winter wheat varieties. The vernalized sprouts of Doridna variety are characterized with higher parameters of mitotic activity of root apical meristems, accumulation of biomass of sprouts at vernalization influence and longer vegetative period comparing with Statna.Conclusion. The trophic conditions of vernalization process cause proliferative activity of meristems, growth reaction of sprouts and speed of transfer to generative development that is effectiveness of vernalization

Genetic Architecture of Flowering-Time Variation in Brachypodium distachyon

The transition to reproductive development is a crucial step in the plant life cycle, and the timing of this transition is an important factor in crop yields. Here, we report new insights into the genetic control of natural variation in flowering time in Brachypodium distachyon, a nondomesticated pooid grass closely related to cereals such as wheat (Triticum spp.) and barley (Hordeum vulgare L.). A recombinant inbred line population derived from a cross between the rapid-flowering accession Bd21 and the delayed-flowering accession Bd1-1 were grown in a variety of environmental conditions to enable exploration of the genetic architecture of flowering time. A genotyping-by-sequencing approach was used to develop SNP markers for genetic map construction, and quantitative trait loci (QTLs) that control differences in flowering time were identified. Many of the flowering-time QTLs are detected across a range of photoperiod and vernalization conditions, suggesting that the genetic control of flowering within this population is robust. The two major QTLs identified in undomesticated B. distachyon colocalize with VERNALIZATION1/PHYTOCHROME C and VERNALIZATION2, loci identified as flowering regulators in the domesticated crops wheat and barley. This suggests that variation in flowering time is controlled in part by a set of genes broadly conserved within pooid grasses.

Effect of plant age and vernalization on bolting, plant growth and enzyme activity of garlic (Allium sativum L.)

In many bulbous plant species that require vernalization, including garlic, the age of the plant and a period of low temperature are important for complete vernalization. However, the response of garlic to vernalization treatment, which regulates development, remains poorly understood. In this study, the effects of vernalization and plant age on garlic growth and development were assessed. Garlic cultivar cv. G064 (bolting type), which is widely cultivated in China, was grown in a plastic tunnel for three different durations (A65, A45 or A25: 65, 45 or 25 days after planting) and then exposed to four vernalization temperatures [T5–0: 5°C/0°C, T10–5: 10°C/5°C, T15–10: 15°C/10°C, T20–15: 20°C/15°C (day/night)] for 40 days in growth chambers. To evaluate the bolting rate, plant growth, and endogenous physiological indexes, leaf and pseudostem samples were taken from all plants after 20 days of treatment and from A25 plants after 40 days of treatment. The results indicate that the response to vernalization varied among garlic plants of different ages, although the patterns were similar among the treatments. In general, vernalization treatment significantly increased the bolting rate in plants at all ages tested, with the youngest plants having the highest bolting rates at 10°C/5°C (28.6%, 40.1% and 50.0% for the A65, A45, and A25 plants, respectively), inhibited vegetative growth (with reductions in plant height observed in all plants except for A65 plants, pseudostem diameter, and green leaf number, especially for the T5–10 treatment) and promoted peroxidase (E.C. 1.15.1.7) and superoxide dismutase (E.C. 1.15.1.1) activities compared with the results observed in the control. The lowest temperature induced the strongest enhancing effect. It seems that a curved parabolic relationship might exist between the vernalization conditions and successful vernalization. Furthermore, the regulation of growth and bolting of plants requiring green-plant vernalization is achievable through the control of plant age (sowing dates) and growth temperature.

Overexpression of an Orchid (Dendrobium nobile) SOC1/TM3-Like Ortholog, DnAGL19, in Arabidopsis Regulates HOS1-FT Expression.

Flowering in the appropriate season is critical for successful reproduction in angiosperms. The orchid species, Dendrobium nobile, requires vernalization to achieve flowering in the spring, but the underlying regulatory network has not been identified to date. The MADS-box transcription factor DnAGL19 was previously identified in a study of low-temperature treated D. nobile buds and was suggested to regulate vernalization-induced flowering. In this study, phylogenetic analysis of DnAGL9 and the MADS-box containing proteins showed that DnAGL19 is phylogenetically closely related to the SOC1-like protein from orchid Dendrobium Chao Parya Smile, DOSOC1. The orchid clade closed to but is not included into the SOC1-1/TM3 clades associated with either eudicots or monocots, suggesting that DnAGL19 is an SOC1-1/TM3-like ortholog. DnAGL19 was found to be highly expressed in pseudobulbs, leaves, roots, and axillary buds but rarely in flowers, and to be substantially upregulated in axillary buds by prolonged low-temperature treatments. Overexpression of DnAGL19 in Arabidopsis thaliana resulted in a small but significantly reduced time to bolting, suggesting that flowering time was slightly accelerated under normal growth conditions. Consistent with this, the A. thaliana APETELA1 (AP1) gene was expressed at an earlier stage in transgenic lines than in wild type plants, while the FLOWERING LOCUS T (FT) gene was suppressed, suggesting that altered regulations on these transcription factors caused the weak promotion of flowering. HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE 1 (HOS1) was slightly activated under the same conditions, suggesting that the HOS1-FT module may be involved in the DnAGL19-related network. Under vernalization conditions, FT expression was significantly upregulated, whereas HOS1 expression in the transgenic A. thaliana has a level similar to that in wild type. Taken together, these results suggest that DnAGL19 controls the action of the HOS1-FT module depending on temperature cues, which could contribute to regulation of D. nobile flowering time. These data provide insights into how flowering is fine-tuned in D. nobile to acclimate the plant to seasonal changes in temperature.