Vernalization Treatment Research Articles

Disruption of IQM5 delays flowering possibly through modulating the juvenile-to-adult transition

IQ motif-containing protein 5 (IQM5) is the fifth member of the IQM family in Arabidopsis, which is an IQ motif-containing family. However, no functional characterizations have been performed using the IQM5 protein in Arabidopsis thaliana. Here, we showed that the IQM5 gene is involved in the regulation of flowering in Arabidopsis. The IQM5 mutants iqm5-1 and iqm5-2 displayed a later-flowering phenotype under both long-day and short-day conditions when compared with wild type. After gibberellic acid or paclobutrazol (PAC) treatments, iqm5-1 and iqm5-2 displayed similar flowering phenotype or PAC sensitivity to wild type. Meanwhile, iqm5-1 and iqm5-2 showed the same flowering ratio as wild type after a vernalization treatment. In addition, disrupting IQM5 increased the transcript level of FLOWERING LOCUS C in both shoot apical meristems and leaves, and decreased that of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 15 in leaves, but did not change the expression of other key genes in the flowering time-related pathway. In addition, the number of abaxial trichomes in both iqm5-1 and iqm5-2 is lower than that in the wild type. Thus, disruption of IQM5 delays flowering possibly through modulating the juvenile-to-adult transition.

Identification of Flowering-Related Genes Responsible for Differences in Bolting Time between Two Radish Inbred Lines.

Late bolting after cold exposure is an economically important characteristic of radish (Raphanus sativus L.), an important Brassicaceae root vegetable crop. However, little information is available regarding the genes and pathways that govern flowering time in this species. We performed high-throughput RNA sequencing analysis to elucidate the molecular mechanisms that determine the differences in flowering times between two radish lines, NH-JS1 (late bolting) and NH-JS2 (early bolting). In total, 71,188 unigenes were identified by reference-guided assembly, of which 309, 788, and 980 genes were differentially expressed between the two inbred lines after 0, 15, and 35 days of vernalization, respectively. Among these genes, 218 homologs of Arabidopsis flowering-time (Ft) genes were identified in the radish, and 49 of these genes were differentially expressed between the two radish lines in the presence or absence of vernalization treatment. Most of the Ft genes up-regulated in NH-JS1 vs. NH-JS2 were repressors of flowering, such as RsFLC, consistent with the late-bolting phenotype of NH-JS1. Although, the functions of genes down-regulated in NH-JS1 were less consistent with late-bolting characteristics than the up-regulated Ft genes, several Ft enhancer genes, including RsSOC1, a key floral integrator, showed an appropriate expression to the late-bolting phenotype. In addition, the patterns of gene expression related to the vernalization pathway closely corresponded with the different bolting times of the two inbred lines. These results suggest that the vernalization pathway is conserved between radish and Arabidopsis.

Identification of vernalization responsive genes in the winter wheat cultivar Jing841 by transcriptome sequencing.

This study aimed to identify vernalization responsive genes in the winter wheat cultivar Jing841 by comparing the transcriptome data with that of a spring wheat cultivar Liaochun10. For each cultivar, seedlings before and after the vernalization treatment were sequenced by Solexa/Illumina sequencing. Genes differentially expressed after and before vernalization were identified as differentially expressed genes (DEGs) using false discovery rate (FDR) ≤ 0.001 and |log2 (fold change)|>1 as cutoffs. The Jing841-specific DEGs were screened and subjected to functional annotation using gene ontology (GO) database. Vernalization responsive genes among the specific genes were selected for validation by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and the expression change over the time was investigated for the top 11 genes with the most significant expression differences. A total of 138,062 unigenes were obtained. Overall, 636 DEGs were identified as vernalization responsive genes including some known genes such as VRN-1 and COR14a, and some unknown contigs. The qRT-PCR validated changes in the expression of 18 DEGs that were detected by RNA-seq. Among them, 11 genes displayed four different types of expression patterns over time during the 30-day-long vernalization treatment. Genes or contigs such as VRN-A1, COR14a, IRIP, unigene1806 and Cl18953. Contig2 probably have critical roles in vernalization.

Identification of Earliness Per Se Flowering Time Locus in Spring Wheat through a Genome‐Wide Association Study

Identification of earliness per se (Eps) flowering time loci in spring wheat are troublesome due to confounding effects of vernalization and photoperiod responses. The Wheat Association Mapping Initiative panel of 287 elite lines was assessed to identify genomic regions associated with Eps and to understand the effects of vernalization and photoperiod treatments in spring wheat. The panel was grown under field conditions with four different treatments: (i) vernalization, where 1‐d germinated seeds were kept at 4°C for 6 to 8 wk; (ii) extended photoperiod treatment, from seedling emergence to 10 d after anthesis in the field; (iii) treatments (i) and (ii) in combination; and (iv) a control treatment without either (i) or (ii). The combined vernalization and photoperiod treatments had the greatest effect in advancing the flowering time (4 d). Genome‐wide association study in this panel on treatment (iii) detected a locus for Eps in chromosome 1D at 163 to 167 cM. An analysis of the flowering time data on this panel from 19 international environments did not show the presence of Eps in chromosome 1D, indicating the possible masking effect of vernalization and photoperiod genes. This study also validated the diagnostic marker—a transcription factor in the circadian clock input pathway called Triticum aestivum EARLY FLOWERING 3—that is associated with Eps in chromosome 1D and can be used for marker‐assisted selection.

Cloning and characterization of TaMBD6 homeologues encoding methyl-CpG-binding domain proteins in wheat

DNA methylation is a major epigenetic marker in plants that plays a crucial role in transcriptional and developmental regulation. The DNA methylation ‘code’ is thought to be ‘read’ by a set of proteins containing methyl-CpG-binding domain (MBD). However, little is known about MBD genes in common wheat (Triticum aestivum L.). Here, we report the isolation and characterization of TaMBD6 and its homeologues (TaMBD6_A, TaMBD6_B, and TaMBD6_D) in hexaploid wheat. The cDNA was quite different among the three homeologues and InDel mutations were detected in 5′-UTR and coding region. Two types of TRs (tandem repeats) -- TR1 (57 bp) and TR2 (39 bp) -- occurred in the coding region. TaMBD6_B harbored five copies of TR1 and two copies of TR2. In contrast, TaMBD6_A lacked 30 bp between the 2nd and 3rd copy of TR1, while TaMBD6_D was missing two copies of TR1 but had three copies of TR2. TaMBD6_A, TaMBD6_B, and TaMBD6_D encoded 435, 446, and 420 amino acids, respectively. Structural analysis of TaMBD6 protein indicated that each of the three homeologues had an identical MBD domain at the N-terminal, as well as a typical nuclear localization signal. Although genomics analysis showed that two introns were included, the length of the first intron varied from 3100 bp to 3471 bp and their sequences were very different. Expression analysis demonstrated that the transcription level of TaMBD6 began to increase gradually in developing grains at 15 days after pollination while decreasing significantly in endosperm and embryo tissues during germination. Expression of TaMBD6 appeared to be positively correlated with starch metabolism in the endosperm but was negatively correlated with embryo formation and sprouting. We were also interested to learn that TaMBD6 homeologues were differentially expressed in developing wheat plants and that their expression patterns were variously affected by vernalization treatment. Further investigation revealed that TaMBD6 was induced by prolonged chilling, indicating that the protein is potentially involved in regulating the developmental transition from vegetative to reproductive stages. Although the homeologues generally showed similar differential expression patterns, TaMBD6_D and TaMBD6_B contribute more to the processes of grain development and germination while TaMBD6_A is predominant in mature plants.

Plantlet regeneration through somatic embryogenesis in Nordmann’s fir (Abies nordmanniana)

I studied the influence of various combinations of auxin and cytokinin concentrations, and the increased content of zinc and enzymatic casein hydrolizate in SH medium on initiation and proliferation of embryogenic callus of Abies nordmanniana (Steven) Spach. Additionally, the effect of ABA, PEG-4000 and different wavelengths on the maturation of somatic embryos was tested. The use of optimum composition of modified SH medium with BA, KIN and 2.4-D while simultaneously ensuring appropriate external conditions resulted in 15.5 % embryogenesis. Finally, satisfactory results of micropropagation of A. nordmanniana by somatic embryogenesis were obtained providing seven lines of embryogenic callus with high proliferation capacity. Those lines gave properly developed seedlings in white LED light with a wavelength of 400-700 nm, preceded by eight-week vernalization treatment of the callus. This paper may provide a protocol by which all stages of somatic embryogenesis of A. nordmanniana can be carried out, including the preceding 24-h seed disinfection with NaOCl and PVP, which resulted in 100 % frequency of uninfected zygotic embryos that were capable of starting embryogenesis.

Heading Date QTL in Winter Wheat (Triticum aestivum L.) Coincide with Major Developmental Genes VERNALIZATION1 and PHOTOPERIOD1.

In wheat (Triticum aestivum L.), time from planting to spike emergence is influenced by genes controlling vernalization requirement and photoperiod response. Characterizing the available genetic diversity of known and novel alleles of VERNALIZATION1 (VRN1) and PHOTOPERIOD1 (PPD1) in winter wheat can inform approaches for breeding climate resilient cultivars. This study identified QTL for heading date (HD) associated with multiple VRN1 and PPD1 loci in a population developed from a cross between two early flowering winter wheat cultivars. When the population was grown in the greenhouse after partial vernalization treatment, major heading date QTLs co-located with the VRN-A1 and VRN-B1 loci. Copy number variation at the VRN-A1 locus influenced HD such that RIL having three copies required longer cold exposure to transition to flowering than RIL having two VRN-A1 copies. Sequencing vrn-B1 winter alleles of the parents revealed multiple polymorphisms in the first intron that were the basis of mapping a major HD QTL coinciding with VRN-B1. A 36 bp deletion in the first intron of VRN-B1 was associated with earlier HD after partial vernalization in lines having either two or three haploid copies of VRN-A1. The VRN1 loci interacted significantly and influenced time to heading in field experiments in Louisiana, Georgia and North Carolina. The PPD1 loci were significant determinants of heading date in the fully vernalized treatment in the greenhouse and in all field environments. Heading date QTL were associated with alleles having large deletions in the upstream regions of PPD-A1 and PPD-D1 and with copy number variants at the PPD-B1 locus. The PPD-D1 locus was determined to have the largest genetic effect, followed by PPD-A1 and PPD-B1. Our results demonstrate that VRN1 and PPD1 alleles of varying strength allow fine tuning of flowering time in diverse winter wheat growing environments.

Genetic and physical mapping of the earliness per se locus Eps-A (m) 1 in Triticum monococcum identifies EARLY FLOWERING 3 (ELF3) as a candidate gene.

Wheat cultivars exposed to optimal photoperiod and vernalization treatments still exhibit differences in flowering time, referred to as earliness per se (Eps). We previously identified the Eps-Am1 locus from Triticum monococcum and showed that the allele from cultivated accession DV92 significantly delays heading time and increases the number of spikelets per spike relative to the allele from wild accession G3116. Here, we expanded a high-density genetic and physical map of the Eps-Am1 region and identified the wheat ortholog of circadian clock regulator EARLY FLOWERING 3 (ELF3) as a candidate gene. No differences in ELF3 transcript levels were found between near-isogenic lines carrying the DV92 and G3116 Eps-Am1 alleles, but the encoded ELF3 proteins differed in four amino acids. These differences were associated with altered transcription profiles of PIF-like, PPD1, and FT1, which are known downstream targets of ELF3. Tetraploid wheat lines with combined truncation mutations in the A- and B-genome copies of ELF3 flowered earlier and had less spikelets per spike than the wild-type control under short- and long-day conditions. Both effects were stronger in a photoperiod-sensitive than in a reduced photoperiod-sensitive background, indicating a significant epistatic interaction between PPD1 and ELF3 (P < 0.0001). By contrast, the introgression of the T. monococcum chromosome segment carrying the Eps-Am1 allele from DV92 into durum wheat delayed flowering and increased the number of spikelets per spike. Taken together, the above results support the hypothesis that ELF3 is Eps-Am1. The ELF3 alleles identified here provide additional tools to modulate reproductive development in wheat.Electronic supplementary materialThe online version of this article (doi:10.1007/s10142-016-0490-3) contains supplementary material, which is available to authorized users.

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.

Identifying Stable Reference Genes for qRT-PCR Normalisation in Gene Expression Studies of Narrow-Leafed Lupin (Lupinus angustifolius L.).

Quantitative Reverse Transcription PCR (qRT-PCR) is currently one of the most popular, high-throughput and sensitive technologies available for quantifying gene expression. Its accurate application depends heavily upon normalisation of gene-of-interest data with reference genes that are uniformly expressed under experimental conditions. The aim of this study was to provide the first validation of reference genes for Lupinus angustifolius (narrow-leafed lupin, a significant grain legume crop) using a selection of seven genes previously trialed as reference genes for the model legume, Medicago truncatula. In a preliminary evaluation, the seven candidate reference genes were assessed on the basis of primer specificity for their respective targeted region, PCR amplification efficiency, and ability to discriminate between cDNA and gDNA. Following this assessment, expression of the three most promising candidates [Ubiquitin C (UBC), Helicase (HEL), and Polypyrimidine tract-binding protein (PTB)] was evaluated using the NormFinder and RefFinder statistical algorithms in two narrow-leafed lupin lines, both with and without vernalisation treatment, and across seven organ types (cotyledons, stem, leaves, shoot apical meristem, flowers, pods and roots) encompassing three developmental stages. UBC was consistently identified as the most stable candidate and has sufficiently uniform expression that it may be used as a sole reference gene under the experimental conditions tested here. However, as organ type and developmental stage were associated with greater variability in relative expression, it is recommended using UBC and HEL as a pair to achieve optimal normalisation. These results highlight the importance of rigorously assessing candidate reference genes for each species across a diverse range of organs and developmental stages. With emerging technologies, such as RNAseq, and the completion of valuable transcriptome data sets, it is possible that other potentially more suitable reference genes will be identified for this species in future.

The expression patterns of threeVRNgenes in common wheat (Triticum aestivumL.) in response to vernalization

Common wheat is a widely planted cereal in China, and vernalization is a crucial phase in wheat development. Although three major genes (VRN1, VRN2 and VRN3) are associated with the vernalization response, little is known about their expression profiles during wheat growth. In this study, we observed the spike differentiation process in spring wheat variety XC2 and winter wheat variety J841 and used qRT-PCR to analyze the expression patterns of three VRN genes in the leaves of these wheat varieties during development under vernalization versus non-vernalization treatment under long-day conditions. We also analyzed the expression patterns of VRN1 and VRN3 in the apical meristem. In both spring and winter wheat, the spikes remained at the single ridge state and did not differentiate under vernalization treatment. Spike differentiation completed one week earlier in XC2 spring wheat after vernalization treatment compared with non-vernalization conditions. Vernalization treatment significantly upregulated VRN1 and VRN3 expression in leaves under long-day conditions, whereas VRN2 expression was sharply reduced. The expression of VRN3 was low in shoot apical meristems, while VRN1 was highly expressed in shoot apical meristems when floral primordia began to differentiate and develop, suggesting that VRN1 functions independently in leaves and shoot apical meristems.

Effects of Vernalization, Temperature, and Soil Drying Periods on the Growth and Yield of Chinese Cabbage

Abstract: This study was carried out to determine the effects of vernalization, temperature, and soil water deficit (SD) on mesoph yll cells, growth, and yield of Chinese cabbage ( Brassica campestris L). The palisade parenchyma and spongy tissues of Chinese cabbage were observed under full irrigation and two weeks of SD treatment. These cells were severely collapsed by four weeks SD treatment. The SD treatment had the greatest influence on the growth of Chinese cabbage among the tested treatment factors (vernalization, temperature, and SD), growth significantly decreased by severe drought treatment (four weeks SD treatment). In addition, the relative growth rate, unit leaf rate, leaf area ratio, specific leaf area, and leaf weight ratio were si gnificantly affected by SD treatment; however, other individual factors and their combined treatments did not influence the analyzed growth parameters. The yield under vernalization after high temperature and full irrigation treatments was 3,056 kg/10 a, which was the greatest among all the tested treatments, while four-week SD treatment significantly reduced the yield. Head formation of Chinese cabbage was not altered under SD treatment, and vernalization treatments did not induce bolting. Our results indicat ed that collapsing mesophyll cells and reduced growth and yield were induced by SD treatment. Thus we suggest that optimal irrigation system should be install to avoid or overcome crippling drought conditions in the open field.Additional key words:

Vernalization response of domesticated × wild chickpea progeny is subject to strong genotype by environment interaction

AbstractVernalization insensitivity is a key feature of domesticated chickpea, and its genetic basis is not well understood. We studied vernalization response among hybrid progeny derived from two domesticated × wild crosses. The wild parents are vernalization‐sensitive, late‐flowering genotypes while both domesticated parents are vernalization insensitive. Parental lines and hybrid progeny were tested with (28 days at 4°C) and without vernalization (control). The difference in mean days to flower (∆DTF) between control and vernalization treatments was used to assess the flowering vernalization response. A wide range of ∆DTF values was observed among the hybrid progeny. Strong genotype by environment interaction effect on ∆DTF was observed for the parental accessions and hybrid progeny. We used the ∆DTF values to select vernalization responsive and non‐responsive progeny lines. However, the genotype × environment interaction strongly interfered with our selection. Chickpea breeders interested in using the wild progenitor as a donor of exotic traits should be aware of the possibility of introducing vernalization response alleles that may alter the phenology of their breeding materials in an unpredictable manner.

Environmental and genetic interactions reveal FLOWERING LOCUS C as a modulator of the natural variation for the plasticity of flowering in Arabidopsis.

The timing of flowering initiation depends strongly on the environment, a property termed as the plasticity of flowering. Such plasticity determines the adaptive potential of plants because it provides phenotypic buffer against environmental changes, and its natural variation contributes to evolutionary adaptation. We addressed the genetic mechanisms of the natural variation for this plasticity in Arabidopsis thaliana by analysing a population of recombinant inbred lines derived from Don-0 and Ler accessions collected from distinct climates. Quantitative trait locus (QTL) mapping in four environmental conditions differing in photoperiod, vernalization treatment and ambient temperature detected the folllowing: (i) FLOWERING LOCUS C (FLC) as a large effect QTL affecting flowering time differentially in all environments; (ii) numerous QTL displaying smaller effects specifically in some conditions; and (iii) significant genetic interactions between FLC and other loci. Hence, the variation for the plasticity of flowering is determined by a combination of environmentally sensitive and specific QTL, and epistasis. Analysis of FLC from Don identified a new and more active allele likely caused by a cis-regulatory deletion covering the non-coding RNA COLDAIR. Further characterization of four FLC natural alleles showed different environmental and genetic interactions. Thus, FLC appears as a major modulator of the natural variation for the plasticity of flowering to multiple environmental factors.

Genetic variation in the flowering and yield formation of timothy (Phleum pratense L.) accessions after different photoperiod and vernalization treatments.

Timothy is a perennial forage grass grown commonly in Boreal regions. This study explored the effect of vernalization and photoperiod (PP) on flowering and growth characteristics and how this related to changes in expression of three flowering related genes in accessions from different geographic origin. Large variation was found in accessions in their vernalization and PP responses. In southern accessions vernalization response or requirement was not observed, the heading date remained unchanged, and plants flowered without vernalization. On the contrary, northern types had obligatory requirement for vernalization and long PP, but the tiller elongation did not require vernalization at 16-h PP. Longer vernalization or PP treatments reduced the genotypical differences in flowering. Moreover, the vernalization saturation progressed stepwise from main tiller to lateral tillers, and this process was more synchronized in southern accessions. The expression of PpVRN1 was associated with vernalization while PpVRN3 accumulated at long PP. A crucial role for PpVRN3 in the transition to flowering was supported as in southern accession the transcript accumulated in non-vernalized plants after transfer to 16-h PP, and the apices transformed to generative stage. Differences in vernalization requirements were associated with variation in expression levels of PpVRN1 and PpVRN3, with higher expression levels in southern type. Most divergent transcript accumulation of PpMADS10 was found under different vernalization conditions. These differences between accessions can be translated into agronomic traits, such as the tiller composition of canopy, which affects the forage yield. The southern types, with minimal vernalization response, have fast re-growth ability and rapidly decreasing nutritive value, whereas northern types grow slowly and have better quality. This information can be utilized in breeding for new cultivars for longer growing seasons at high latitudes.

The relationship between allelic variations ofVrn-1andPpd-1and agronomic traits in Korean wheat cultivars

The allelic variations at the Vrn-1 and Ppd-1 loci of Korean wheat cultivars were determined to evaluate their effects on agronomic traits and response to vernalization treatment. Korean wheat cultivars displayed high frequency of Vrn-D1a and Ppd-B1b alleles, but all of the tested cultivars carried vrn-A1, vrn-B1, Ppd-A1b and Ppd-D1a alleles at the corresponding loci. Regardless of vernalization treatments, Korean wheat cultivars carrying the vrn-D1 allele showed longer days to flag leaf unfolding than those with the Vrn-D1a allele. Unvernalized cultivars carrying the vrn-D1 allele also exhibited larger final leaf number than those with the Vrn-D1a allele. However, there were no significant differences in the response of the Korean wheat cultivars to vernalization treatment based on allelic variation at the Ppd-1 loci. With respect to agronomic traits, the Vrn-D1a allele was related to increased grain yield and decreased thousand kernel weight compared to the vrn-D1 allele. Cultivars carrying both Vrn-D1a and Ppd-B1b alleles produced higher grain yield (5.5 tons/ha) than those with the vrn-D1 and Ppd-B1b alleles (5.0 tons/ha).

Identification of three FLOWERING LOCUS C genes responsible for vernalization response in radish (Raphanus sativus L.)

Raphanus sativus L. is grown worldwide and used as fresh vegetables. In the Brassicaceae family, the FLOWERING LOCUS C (FLC) gene is a key regulator of flowering time and explains a large part of natural flowering time variation and the vernalization response. Here we report three FLC orthologous genes RsFLC1, RsFLC2, and RsFLC3 in R. sativus identified from the de novo assembled transcriptome. The sequences of three RsFLC genes have a high similarity to Arabidopsis FLC. Overexpression of each RsFLC gene in Arabidopsis induced late flowering, suggesting that every RsFLC gene functions as a floral repressor. All RsFLC genes were highly expressed in non-vernalized plants, whereas their expression levels significantly decreased by the vernalization treatment. Furthermore, the rate of decrease in their expression was proportional to the length of cold exposure. A significant level of sequence variation exists among RsFLC alleles derived from a variety of Raphanus cultivars, suggesting that RsFLC genes have diverged considerably but still retain essential functions.

Introduced North American Black Henbane (Hyoscyamus niger) Populations are Biennial

AbstractBlack henbane can be either annual or biennial. We investigated which life cycle is found in four introduced western North American populations. Plants were grown in a greenhouse common garden until half were vernalized by exposure to natural winter temperatures, while the other half remained in the greenhouse above 20 C, with 16 h of light and 8 h of dark. In total the plants were monitored 313 d after germination. We measured whether plants bolted, the time it took for bolting to commence, and the size at bolting. All vernalized plants bolted after 117 d of active growth (within 26 d of the end of the vernalization treatment), whereas only 26% of the nonvernalized plants bolted after an average of 278 d of active growth. Vernalized plants bolted at a smaller size than the nonvernalized plants that bolted (28 vs. 41 leaves on average). In the nonvernalized plants, the relationship between time to bolting and size was strong, but not so with the vernalized plants. Our results indicate that introduced black henbane plants are biennial, and that vernalization is more critical to bolting and flowering than reaching a certain size. Nonetheless, the fact that nonvernalized plants were capable of bolting if grown long enough suggests that vernalization is not the only cue that can trigger reproduction in introduced populations.

BdBRD1, a brassinosteroid C-6 oxidase homolog in Brachypodium distachyon L., is required for multiple organ development

Brassinosteroids (BRs), known as a kind of phytohormones, play essential roles in plant growth and development. Although the studies on the BR biosynthesis and signaling are extensive in Arabidopsis, little is known in temperate cereals. In this study, bdbrd1-1, a T-DNA insertion mutant from Brachypodium distachyon, was isolated and characterized in details. The bdbrd1-1 mutant showed lots of cellular and morphogenetic defects, including shortened cell shapes, severe dwarfing, twisted leaves and sterile spikes. Sequencing the flanking fragment of the T-DNA and complementation by genomic DNA in the mutant, confirmed that the developmental defects are caused by the T-DNA insertion in BdBRD1, a possible brassinosteroid C-6 oxidase gene. Application of 24-epicastasterone could partly rescue the bdbrd1-1 dwarfing phenotype. Expression analysis of BdBRD1 suggested that bdbrd1-1 is probably a null mutant and its wild type transcript is expressed in various tissues and highest in the leaf sheaths. Meanwhile, measurements on leaf numbers of the main stems or days to the emergence of the inflorescences suggested that bdbrd1-1 is late-flowering. The late-flowering phenotype could be converted by vernalization treatment, although there lacks a typical FLC gene in B. distachyon. The current data provide an insight into the relationship between BRs biosynthesis and individual development in B. distachyon, an emerging model plant for the temperate cereals.

Genetic variation for the duration of pre-anthesis development in durum wheat and its interaction with vernalization treatment and photoperiod.

A recombinant inbred durum wheat population was grown under three contrasting regimes: long days following vernalization (LDV), long days without vernalization (LD), and short days following vernalization (SDV). The length of several pre-anthesis stages and the number of leaves and the phyllochron were measured. Different groups of genes were involved in determining the phenology in the three treatments, as demonstrated by a quantitative trait locus (QTL) analysis. The length of the period required to reach the terminal spikelet stage was correlated with the time to anthesis only in the case of LDV- and LD-grown plants where the timing of anthesis depended on the final leaf number. However, for SDV-grown plants, anthesis date was more dependent on the length of the period between the terminal spikelet stage and anthesis and was independent of leaf number. The involvement of the phyllochron in determining the duration of pre-anthesis development was also treatment-dependent. QTL mapping of the various flowering time associated traits uncovered some novel loci (such as those associated with the phyllochron), in addition to confirming the presence of several well-established loci.