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Effects of GA treatments on chrysanthemum flowering under LD conditions. (a) GA content in the shoot tips of plants at LT5 and at LT5 + N2. Plants grown for 5 or 7 weeks under normal temperature and LD conditions were used as controls (C5 and C7). (b) The effects of exogenous GA4/7 treatment and 5‐week low‐temperature treatment (LT5) on plant height of 8‐week‐old chrysanthemum. GA was given twice per week for 2 months. (c) The effects of exogenous GA4/7 treatments and 5‐week low‐temperature treatments (LT5) on initial flower bud appearance in control and treated plants. (d) Phenotypes of control and treated plants were observed after 14 weeks. The results are the means of three biological replicates with standard deviations. Asterisks indicate statistically significant differences (Student's t‐test, **P < 0.01). Different letters indicate significant differences according to Duncan's multiple range test (P < 0.05). Scale bars, 5 cm.
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Chrysanthemum (Chrysanthemum morifolium) is well known as a photoperiod‐sensitive flowering plant. However, it has also evolved into a temperature‐sensitive ecotype. Low temperature can promote the floral transition of the temperature‐sensitive ecotype, but little is known about the underlying molecular mechanisms. Here, we identified MADS AFFECTIN...
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Citations
... During the long evolutionary process, chrysanthemums have developed different types of photoperiod-responsive flowering, including SD-dependent autumn chrysanthemum, which blooms in autumn, and summer-autumn chrysanthemum, which blooms in summer to autumn and is less sensitive to photoperiod. The former of these is an obligatory SD chrysanthemum and the latter is a facultative SD chrysanthemum [33,34]. In this study, by comparing the flowering characteristics of different chrysanthemums in response to photoperiod, we found that 'A44', 'C60', and '183' were sensitive to SD conditions and were classified as obligatory SD chrysanthemum, and 'A20', 'C1', 'C27', and 'C31' were not sensitive to SD conditions and were classified as facultative SD chrysanthemum. ...
... Therefore, it was hypothesized that other floral transition pathways might exist in the 'C31' variety (Figures 1 and 4G). In chrysanthemum, in addition to the photoperiod pathway, the vernalization pathway [34], the age pathway [39], and the gibberellin pathway [40] have also been found to be involved in the regulation of flowering, and the joint involvement of multiple pathways is also a question worth investigating. ...
Chrysanthemum × morifolium Ramat. is a globally renowned ornamental flower. It includes numerous varieties, most of which are typical short-day (SD) plants, and the flowering characteristics of different chrysanthemum varieties in response to the photoperiod vary greatly. In this study, seven representative chrysanthemum varieties were selected for a comparative analysis of flowering traits under long-day conditions (16 h/8 h day/night) and short-day conditions (12 h/12 h day/night). It was found that three varieties (‘A44’, ‘C60’, and ‘183’) belonged to obligatory short-day varieties and four varieties (‘A20’, ‘C1’, ‘C27’, and ‘C31’) belonged to facultative short-day varieties. The short-day conditions not only induced earlier flowering but also improved flowering quality in the facultative SD varieties. Different chrysanthemum varieties required different light conditions to complete the vegetative stage and reach the floral competent state. Seven chrysanthemum varieties, ‘A44’, ‘C60’, ‘183’, ‘A20’, ‘C1’, ‘C27’, and ‘C31’, reached a floral competent state in the L20, L20, L22, L22, L18, L20, and L24 periods, respectively, and were most sensitive to SD induction at this time. The expression patterns of key floral genes in the photoperiod pathway were analyzed and it was found that CmCRY1, CmCRY2, CmGI1, CmGI2, and CmCO were mainly expressed in leaves. Then, comparing the expression levels of these genes under LD and SD conditions, the expression of CmGI1, CmGI2, CmCO, and CmFTL were not significantly induced in the obligatory SD varieties, while the expression of them in the facultative SD varieties were induced by SD conditions. This may be the reason why the facultative varieties could respond to SD conditions more quickly to complete the floral transition. In addition, SD induction under different photoperiodic conditions and growth states resulted in differences in the phenotype of flowering. This result provides guidance for the artificial regulation of chrysanthemum flowering and improvement of ornamental quality, as well as clues for analyzing the flowering mechanism of chrysanthemums under different photoperiod conditions.
... Statistical significance is denoted by * * (P < 0.01) and * * * (P < 0.001) using Student's t-test. and in the regulation of temperature-mediated f lowering processes in plants [31,32]. Through the transcriptomic analysis, we identified a member of the OfC3H family gene, OfC3H49, which showed the most pronounced response to high ambient temperature (Fig. 2). ...
Ambient temperature is a pivotal factor in the regulation of the flowering process in plants. In this study, we found that high ambient temperature exerts an inhibitory effect on the flowering of Osmanthus fragrans “Sjigui”. However, the underlying molecular mechanisms remain not fully understood. Through transcriptome analysis, a differently expressed C3H gene OfC3H49 was identified, which is induced by high ambient temperature. OfC3H49 was demonstrated to delay the flowering process of Arabidopsis and to downregulate the expression of flowering-related genes in O. fragrans calli. Further investigation indicates that OfC3H49 as a transcriptional repressor, directly suppresses the expression of the OfSOC1B thereby causing a delay in flowering time. Furthermore, a WRKY transcription factor, OfWRKY17, was identified to be responsive to high ambient temperature, directly binding to the OfC3H49 promoter and enhance OfC3H49 expression. Overexpression of OfWRKY17 in Arabidopsis resulted in a significant delay in flowering and induced the expression of OfC3H49 in O. fragrans calli. Collectively, our findings delineate a regulatory module, OfWRKY17-OfC3H49, which is activated by high ambient temperature and functions as a negative regulator of flowering by suppressing the expression of OfSOC1B in O. fragrans. This study provides novel insights into the molecular mechanisms involved in ambient temperature-mediated flowering control and contributes to the development of molecular breeding strategies for O. fragrans.
... For instance, Oda et al. (2012) isolated three FT-like paralogues from diploid wild chrysanthemum C. seticuspe and found the gene product of CsFTL3 is a key regulator of photoperiodic flowering in chrysanthemum. Lyu et al. (2022) identified MADS AFFECTING FLOWERING 2 (CmMAF2), a putative MADS-box gene, which induces floral transition in response to low temperature independent of day length conditions. CmERF110 interacts with Flowering Locus KH domain homologue (CmFLK) to synergistically regulate the photoperiodic flowering in chrysanthemum . ...
Main conclusion
Multi-locus GWAS detected several known and candidate genes responsible for flowering time in chrysanthemum. The associations could greatly increase the predictive ability of genome selection that accelerates the possible application of GS in chrysanthemum breeding.
Abstract
Timely flowering is critical for successful reproduction and determines the economic value for ornamental plants. To investigate the genetic architecture of flowering time in chrysanthemum, a multi-locus genome-wide association study (GWAS) was performed using a collection of 200 accessions and 330,710 single-nucleotide polymorphisms (SNPs) via 3VmrMLM method. Five flowering time traits including budding (FBD), visible colouring (VC), early opening (EO), full-bloom (OF) and senescing (SF) stages, plus five derived conditional traits were recorded in two environments. Extensive phenotypic variations were observed for these flowering time traits with coefficients of variation ranging from 6.42 to 38.27%, and their broad-sense heritability ranged from 71.47 to 96.78%. GWAS revealed 88 stable quantitative trait nucleotides (QTNs) and 93 QTN-by-environment interactions (QEIs) associated with flowering time traits, accounting for 0.50–8.01% and 0.30–10.42% of the phenotypic variation, respectively. Amongst the genes around these stable QTNs and QEIs, 21 and 10 were homologous to known flowering genes in Arabidopsis; 20 and 11 candidate genes were mined by combining the functional annotation and transcriptomics data, respectively, such as MYB55, FRIGIDA-like, WRKY75 and ANT. Furthermore, genomic selection (GS) was assessed using three models and seven unique marker datasets. We found the prediction accuracy (PA) using significant SNPs identified by GWAS under SVM model exhibited the best performance with PA ranging from 0.90 to 0.95. Our findings provide new insights into the dynamic genetic architecture of flowering time and the identified significant SNPs and candidate genes will accelerate the future molecular improvement of chrysanthemum.
... Although GA20ox paralogs may have redundant functions, only GA20ox1 (GA5) has an impact on plant height (Xu et al. 1995;Rieu et al. 2008). The levels of bioactive GAs or the expression of GA biosynthetic genes are markedly increased in plants carrying either loss-of-function mutations in positive regulatory components or gain-offunction mutations in repressor components (Olszewski et al. 2002;Lyu et al. 2022). Within the intricate signaling network accompanied by hormonal effects, it is crucial to identify the major signal nodes and the proteins that perform important roles. ...
... GA20ox functions in converting GA precursors to the active forms GA 1 and GA 4 (Israelsson et al. 2004). An altered expression of GA20ox genes affects the content of active GAs in various plant species (Plackett et al. 2012;Park et al. 2015;Lopez-Cristoffanini et al. 2019;Lyu et al. 2022). Among the Arabidopsis GA20ox genes, GA20ox1 exhibits the highest levels of expression during vegetative growth and loss of GA20ox1 causes severe dwarfism (Rieu et al. 2008). ...
Key message
AtHSPR forms a complex with KNAT5 and OFP1 to regulate primary root growth through GA-mediated root meristem activity. KNAT5–OFP1 functions as a negative regulator of AtHSPR in response to GA.
Abstract
Plant root growth is modulated by gibberellic acid (GA) signaling and depends on root meristem maintenance. ARABIDOPSIS THALIANA HEAT SHOCK PROTEIN-RELATED (AtHSPR) is a vital regulator of flowering time and salt stress tolerance. However, little is known about the role of AtHSPR in the regulation of primary root growth. Here, we report that athspr mutant exhibits a shorter primary root compared to wild type and that AtHSPR interacts with KNOTTED1-LIKE HOMEOBOX GENE 5 (KNAT5) and OVATE FAMILY PROTEIN 1 (OFP1). Genetic analysis showed that overexpression of KNAT5 or OFP1 caused a defect in primary root growth similar to that of the athspr mutant, but knockout of KNAT5 or OFP1 rescued the short root phenotype in the athspr mutant by altering root meristem activity. Further investigation revealed that KNAT5 interacts with OFP1 and that AtHSPR weakens the inhibition of GIBBERELLIN 20-OXIDASE 1 (GA20ox1) expression by the KNAT5–OFP1 complex. Moreover, root meristem cell proliferation and root elongation in 35S::KNAT5athspr and 35S::OFP1athspr seedlings were hypersensitive to GA3 treatment compared to the athspr mutant. Together, our results demonstrate that the AtHSPR–KNAT5–OFP1 module regulates root growth and development by impacting the expression of GA biosynthetic gene GA20ox1, which could be a way for plants to achieve plasticity in response to the environment.
... Day-neutral chrysanthemums characteristically have equal leaf numbers and primary stem lengths when grown under both short-and long-day photoperiods [1,3]. In addition, studies have shown that the photoperiodic pathway, vernalization pathway, gibberellin pathway, and age pathway are all involved in regulating the flowering time of chrysanthemums [7,[13][14][15][16][17][18][19]. However, these studies have mainly focused on chrysanthemum cultivars that respond to short-day photoperiods to flower, and there have been few studies on the flowering mechanism of day-neutral chrysanthemums; furthermore, the related traits affecting their ornamental value are also lacking research. ...
... Agronomy 2023, 13, 2107 ...
Day-neutral multiflora chrysanthemums can flower throughout the year without being influenced by daylength and have great application value in gardens. Studying heterosis and the genetic basis of important traits in day-neutral chrysanthemums can accelerate the breeding of new cultivars. In this research, a genetic population was constructed by crossing 135 F1 hybrid progeny from the day-neutral chrysanthemum ‘82-81-19’ (female parent) and the late-flowering chrysanthemum ‘388Q-76’ (male parent). Six traits, including abnormal (crown) bud, plant height, plant crown width, budding date, full flowering date, and number of petal layers, were selected for inheritance and heterosis analyses, and a single-generation major gene plus polygene mixed inheritance model was used to perform mixed inheritance analysis on these traits. The results indicated that the six traits were widely segregated in the F1 population, with the coefficient of variation (CV) ranging from 30% to 84%. The phenomena of heterosis and extra-parent segregation existed generally in F1 progeny, and the ratio of heterosis value of mid-parents (RHm) for the six traits was 45.5%, 2%, 2%, 6%, 6%, and −0.3%, respectively. The mixed genetic analysis showed that the abnormal (crown) bud and budding date were fitted to the B-3 model and controlled by two pairs of additive major genes. The plant height and plant crown width were fitted to the A-0 model, and no major gene was detected. The full flowering date was fitted to the A-1 model and was controlled by one pair of major genes. The number of petal layers was fitted to the B-1 model and controlled by two pairs of additive–dominant major genes. The heritabilities of major genes for abnormal bud, budding date, full flowering date, and the number of petal layers were 1.0, 0.9871, 0.7240, and 0.5612, respectively, indicating that these traits were less affected by environmental factors. Using a percentile scoring method, eight day-neutral chrysanthemum genotypes were selected from the hybrid progeny.
Environmental temperature significantly affects plant growth and development, particularly flower development. In pepper (Capsicum annuum), the molecular mechanisms underlying temperature-mediated floral organ development remain unclear. Gibberellins (GAs) are key plant hormones regulating growth and development, including flower development, and the CaGA20ox gene family may play a crucial role in this process due to its involvement in GA biosynthesis. In this study, we comprehensively analyzed the CaGA20ox gene family across six pepper genomes (‘Zhangshugang’, ‘Zunla’, ‘Chiltepin’, ‘CM334’, ‘Ca59’, and ‘T2T’) to explore their roles in flower development and temperature stress response, identifying five to six genes per genome. These genes exhibited distinct expression patterns across different tissues and developmental stages, with some members showing higher expression in specific floral organs, particularly pistils. Our results revealed that temperature significantly impacts pepper flower development and GA content, with lower temperatures enhancing antioxidant capacity and increasing GA levels. Specifically, the expression levels of four CazGA20ox genes (CazGA20ox1, CazGA20ox2, CazGA20ox4, and CazGA20ox6) were significantly influenced by temperature changes. Our systematic analysis of the role of the CaGA20ox gene family in temperature-mediated pepper flower development provides a foundation for further studies on the molecular mechanisms as well as the development of improved pepper varieties.
Edible chrysanthemum (Chrysanthemum morifolium Ramat.), widely consumed in Asia, is rich in bioactive compounds such as polyphenols, flavonoids, and amino acids. Optimizing cultivation temperature is critical for maximizing both yield and quality, especially under the challenges posed by climate change. This study evaluated the growth performance, photosynthetic characteristics, and metabolite accumulation of the ‘Taiwan Hangju No. 1’ variety under five day/night temperature regimes (15/13 °C, 20/15 °C, 25/20 °C, 30/25 °C, and 35/30 °C) over a 220-day period in an artificial climate greenhouse. The 25/20 °C regime promoted the best overall growth, with the highest yields of bud-leaves and flowers, and supported the highest net photosynthetic rate, indicating optimal carbon assimilation under moderate temperatures. In contrast, stomatal conductance, respiration rate, and transpiration rate increased with temperature, peaking at 35/30 °C. Water use efficiency was greatest at 15/13 °C. Bioactive compound accumulation exhibited complex and organ-specific responses to temperature. The concentration of polyphenols, luteolin, and caffeoylquinic acid derivatives (CQAs) increased with temperature in both bud-leaves and flowers, free amino acids decreased in bud-leaves with rising temperature, reaching a peak at 15/13 °C, and flavonoid concentration peaked at 35/30 °C. In flowers, free amino acids accumulated most at 20/15 °C, and flavonoids peaked at 25/20 °C. The differing yields of bud-leaves and flowers under various temperature conditions contributed to variation in the total content of functional compounds. Except for free amino acids, the total of other functional compounds in bud-leaves was highest at 30/25 °C. The total content of all functional compounds in flowers was highest at 25/20 °C. This study demonstrated that 25/20 °C provides the best balance between growth, photosynthetic efficiency, and accumulation of key bioactive compounds and is therefore recommended as the optimal cultivation temperature for ‘Taiwan Hangju No. 1’. These findings reveal temperature-dependent and organ-specific metabolic adjustments, suggesting that moderate warming may enhance crop quality if managed carefully. The results provide a scientific basis for climate-adaptive cultivation strategies of edible chrysanthemums in subtropical regions.
The flowering time of Chrysanthemum morifolium predominantly depends on day length but is also sensitive to ambient temperature. However, the mechanisms underlying the response of chrysanthemum to ambient temperature are mainly unknown. This study identified a MADS-box transcription factor called CmFLC-like, a representative low ambient temperature-responsive factor induced in chrysanthemum leaves and shoot apical meristems at 15°C. Subsequently, CmFLC-like localizes to the cell nucleus and membrane and functions as a transcriptional repressor. CmFLC-like overexpression made plants more sensitive to low-temperature-induced late flowering, whereas the chimeric activator CmFLC-like-VP64 was less sensitive at 15°C, indicating that CmFLC-like was involved in thermosensory flowering. Transcriptome profiling of CmFLC-like transgenic plants suggested that the potential target genes for low ambient temperature-responsive CmFLC-like regulation are predominantly flowering integrators, MADS-box transcription factors, and AP2 genes. Subsequent examination revealed that the orchestrated repression of CmAFL1 and CmFTL3 by CmFLC-like was mediated by its direct binding to the CArG-box element of their promoters. This study offers novel insights into the molecular mechanisms underlying chrysanthemum flowering and highlights the essential role of CmFLC-like proteins in the thermosensory pathway.
