Explore the vast range of titles available.

CONSTANS is an evolutionarily-conserved central component of the genetic pathway that controls the onset of flowering in response to daylength. However, the specific biochemical mechanism by which the CONSTANS protein regulates the expression of its target genes remains largely unknown. By using a combination of cell-based expression analysis and in vitro DNA binding studies, we have demonstrated that CONSTANS possesses transcriptional activation potential and is capable of directly binding to DNA. CONSTANS was found to bind DNA via a unique sequence element containing a consensus TGTG(N2-3)ATG motif. This element is present in tandem within the FLOWERING LOCUS T promoter and is sufficient for CO binding and activity. The conserved CCT (CONSTANS, CONSTANS-like and TOC1) domain of CONSTANS was shown to be required for its recruitment to the DNA motif and other CCT-containing proteins were also found to have the ability to regulate gene expression via this element. The CCAAT box, which has been previously hypothesized as a recruitment site for complexes containing the CONSTANS protein, potentiated CONSTANS-mediated activation but was not essential for CONSTANS recruitment to a target promoter or for its activity as a transcriptional factor.

Appropriate control of flowering time is crucial for crop yield and the reproductive success of plants. Flowering can be induced by a number of molecular pathways that respond to internal and external signals. In Arabidopsis, expression of the key florigenic signal ( ) is positively regulated by CONSTANS (CO) a BBX protein sharing high sequence similarity with 16 CO-like proteins. Within this study, we investigated the role of the Arabidopsis - ( , whose role in flowering control was unknown. We demonstrate that, unlike CO, COL4 is a flowering repressor in long days (LD) and short days (SD) and acts on the expression of and -like genes as well as on ( ). Reduction of expression level leads to an increase of and ( ) expression and to accelerated flowering, while the increase of expression causes a flowering delay. Further, the observed co-localization of COL4 protein and CO in nuclear speckles supports the idea that the two act as an antagonistic pair of transcription factors. This interaction may serve the fine-tuning of flowering time control and other light dependent plant developmental processes.

Summary Branching is a major determinant of crop yield, and enables vigorous shoot growth and the production of a dense canopy. Phytochrome A signal transduction 1 (PAT1) positively regulates phytochrome A signal transduction in response to light, but its effects on branching remain unknown. In this study, we mapped PAT1, and revealed a previously unknown role related to branching and flowering in leafy Brassica juncea. Earlier and increased branching was observed when PAT1 expression was down‐regulated, implying that PAT1 negatively regulates shoot branching. Additionally, down‐regulated PAT1 expression reversed the inhibited branching induced by far‐red light, suggesting PAT1 is involved in the shade avoidance response. PAT1 negatively regulated branching only after bud initiation. The observed interaction between PAT1 and BRC1 implied that PAT1 influences bud outgrowth in a BRC1‐dependent manner. Biochemical and genetic evidence indicate that PAT1 directly interacts with CONSTANS‐LIKE 13 (COL13), which negatively regulates flowering, with the resulting PAT1–COL13 complex mediating shoot branching and flowering. Our findings reveal a new crosstalk modality between phytochrome signalling and flowering pathways during the regulation of shoot branching and flowering. The data presented herein may be useful for future studies involving the editing of the GRAS family transcription factor PAT1 gene to enhance crop productivity and enable earlier harvesting.

Background Cymbidium sinense is an orchid that is typically used as a potted plant, given its high-grade ornamental characteristics, and is most frequently distributed in China and SE Asia. The inability to strictly regulate flowering in this economically important potted and cut-flower orchid is a bottleneck that limits its industrial development. Studies on C. sinense flowering time genes would help to elucidate the mechanism regulating flowering. There are very few studies on the genetic regulation of flowering pathways in C. sinense . Photoperiod significantly affects the flowering of C. sinense , but it was unknown how the CONSTANS gene family is involved in regulating flowering. Results In this study, eight CONSTANS-like genes were identified and cloned. They were divided into three groups based on a phylogenetic analysis. Five representative CsCOL genes ( CsCOL3/4/6/8/9 ) were selected from the three groups to perform expression characterization and functional study. CsCOL3/4/6/8/9 are nucleus-localized proteins, and all five CsCOL genes were expressed in all organs, mainly in leaves followed by sepals. The expression levels of CsCOL3/4 (group I) were higher in all organs than other CsCOL genes. Developmental stage specific expression revealed that the expression of CsCOL3/4/9 peaked at the initial flowering stage. In contrast, the transcript level of CsCOL6/8 was highest at the pedicel development stage. Photoperiodic experiments demonstrated that the transcripts of the five CsCOL genes exhibited distinct diurnal rhythms. Under LD conditions, the overexpression of CsCOL3/4 promoted early flowering, and CsCOL6 had little effect on flowering time, whereas CsCOL8 delayed flowering of Arabidopsis thaliana . However, under SD conditions, overexpression of CsCOL4/6/8 promoted early flowering and the rosette leaves growth, and CsCOL3 induced flower bud formation in transgenic Arabidopsis . Conclusion The phylogenetic analysis, temporal and spatial expression patterns, photoperiodic rhythms and functional study indicate that CsCOL family members in C. sinense were involved in growth, development and flowering regulation through different photoperiodic pathway. The results will be useful for future research on mechanisms pertaining to photoperiod-dependent flowering, and will also facilitate genetic engineering-based research that uses Cymbidium flowering time genes.

Nuclear Factor Y (NF-Y) is a heterotrimeric transcription factor that binds CCAAT elements. The NF-Y trimer is composed of a Histone Fold Domain (HFD) dimer (NF-YB/NF-YC) and NF-YA, which confers DNA sequence specificity. NF-YA shares a conserved domain with the CONSTANS, CONSTANS-LIKE, TOC1 (CCT) proteins. We show that CONSTANS (CO/B-BOX PROTEIN1 BBX1), a master flowering regulator, forms a trimer with Arabidopsis thaliana NF-YB2/NF-YC3 to efficiently bind the CORE element of the FLOWERING LOCUS T promoter. We term this complex NF-CO. Using saturation mutagenesis, electrophoretic mobility shift assays, and RNA-sequencing profiling of co, nf-yb, and nf-yc mutants, we identify CCACA elements as the core NF-CO binding site. CO physically interacts with the same HFD surface required for NF-YA association, as determined by mutations in NF-YB2 and NF-YC9, and tested in vitro and in vivo. The co-7 mutation in the CCT domain, corresponding to an NF-YA arginine directly involved in CCAAT recognition, abolishes NF-CO binding to DNA. In summary, a unifying molecularmechanism of CO function relates it to the NF-YA paradigm, as part of a trimeric complex imparting sequence specificity to HFD/DNA interactions. It is likely that members of the large CCT family participate in similar complexes with At-NF-YB and At-NF-YC, broadening HFD combinatorial possibilities in terms of trimerization, DNA binding specificities, and transcriptional regulation.

Pear ( Pyrus L.) is a significant commercial fruit globally, with diverse species exhibiting variations in their flowering periods due to environmental factors. CONSTANS-like ( COL ) genes, known from previous studies in Arabidopsis , are key regulators of flowering time by sensing photoperiod. However, the evolutionary history and functions of COL genes in different pear species remain unclear. In this study, we identified a total of 79 COL genes in different pear species, including 12 COL genes in Pyrus bretschneideri ‘DangshanSuli’, 9 in Pyrus ussuriensis  ×  hybrid ‘Zhongai 1’, 11 in Pyrus communis ‘Bartlett’, 13 in Pyrus betulifolia , 18 in Pyrus pyrifolia ‘Cuiguan’, 16 in Pyrus pyrifolia ‘Nijisseiki’. Analysis of gene structure, phylogenetic tree, and multiple sequences provided valuable insights into the fundamental understanding of COL genes in pear. The impact of selection pressure on the PbrCOLs in Chinese white pear was assessed using Ka / Ks , revealing that the evolution rate of PbrCOLs was influenced by purification selection factors. The study also revealed different tissue-specific expression patterns of PbrCOLs under varying light quality. Real-time quantitative PCR revealed that under natural light conditions, the expression patterns of PbrCOL2 , PbrCOL3 , and PbrCOL4 are similar to previous studies on CONSTANS gene in Arabidopsis , with increased expression levels during the day and decreased levels at night. However, PbrCOL1 , PbrCOL6 , and PbrCOL9 exhibit different expression patterns, with decreased expression levels both during the day and at night. After red light treatment, high expression of PbrCOL3 and PbrCOL4 was observed at night, while the expression patterns of the other four genes did not show significant changes. Following blue light treatment, the expression peaks of PbrCOL1 and PbrCOL6 occurred during the night, showing opposite expression patterns compared to the study in Arabidopsis . The overexpression of PbrCOL3 significantly increase the chlorophyll content in pear seedlings, and its expression significantly affected the expression of other key flowering-related genes. Also, overexpression of PbrCOL3 resulted in a late-flowering phenotype in Arabidopsis. These findings indicate diverse responsive mechanisms and functions of PbrCOL genes on flowering time in pear. In conclusion, this study established a foundation for a deeper understanding of the specific roles of PbrCOLs in regulating the reproductive development of pear, particularly in the context of the photoperiodic flowering process.

CONSTANS-LIKE (COL) genes are considered the core components in photoperiod regulation and contribute to flowering regulation. Liriodendron chinense is a rare relict plant of the Magnoliaceae family. Having beautiful flowers like a tulip, L. chinense is now popularly used as an ornamental tree species. However, the COL genes of L. chinense have not yet been investigated. Here, we multidimensionally identify and characterize the COL genes in L. chinense, including their phylogenetic relationships, conserved motifs, cis-acting elements, expression patterns, and ectopic transformations. Nine LcCOL genes were identified across the L. chinense genome and were located on seven chromosomes. These nine LcCOL genes could be phylogenetically clustered into three groups (I, II, and III), with three, five and one COL members in each group, respectively. Real-time quantitative PCR (RT-qPCR) showed that the expression of LcCOL genes exhibited diverse patterns in various tissues. Moreover, LcCO and LcCOL3 displayed seasonal patterns, indicating that LcCO and LcCOL3 may play roles in flowering regulation. To analyze the function of the LcCO gene, we subsequently transferred LcCO into Arabidopsis thaliana via agrobacterium inflorescence infection, and found that overexpression of LcCO in A. thaliana caused earlier flowering and fewer rosette leaves under long-day condition. By RT-qPCR, we show that overexpression of LcCO co-regulates the expression of AtFLC, AtSOC1 and AtFT in transgenic Arabidopsis. Our study identified the COL members in L. chinense genome and laid a cornerstone for further functional characterization of LcCOL genes.

PREMISE OF THE STUDY: Introgression of adaptive alleles between hybridizing species is likely an important mechanism to generate new genetic variation for adaptation to rapidly changing environmental conditions. Oaks provide a model for the study of adaptive gene introgression because environmental selection maintains high interspecific differentiation at a few outlier loci and species‐specific adaptations despite recurrent interspecific gene flow. Previously, we identified a CONSTANS‐like gene under strong divergent selection between drought‐tolerant Quercus ellipsoidalis and drought‐averse Quercus rubra. Neighboring (parapatric) populations of both species were fixed for alternate alleles, Q. ellipsoidalis for allele 138 and Q. rubra for allele 141. METHODS: In this study, we analyzed introgression of these outlier alleles in sympatric and in parapatric Q. rubra/Q. ellipsoidalis populations. KEY RESULTS: We found evidence that environmental selection affected the level and direction of outlier allele introgression. Thus, in the face of symmetric interspecific gene flow, outlier allele introgression was asymmetric and introgression of allele 138 into Q. rubra was consistently higher than introgression of allele 141 into Q. ellipsoidalis in sympatric populations, but the opposite pattern was found in parapatric populations. Furthermore, the rate of introgression of outlier alleles between species in sympatric stands was related to soil quality (i.e., soil water holding capacity, nutrient availability). CONCLUSIONS: This pattern suggests that introgression of adaptive genes between these two red oak species is strongly affected by environmental selection and is an important mechanism for species’ adaptation to changing environmental conditions in a changing climate.

Background In Arabidopsis , a long day flowering plant, CONSTANS ( CO ) acts as a transcriptional activator of flowering under long day (LD) condition. In rice, a short day flowering plant, Hd1 , the ortholog of CO , plays dual functions in respond to day-length, activates flowering in short days and represses flowering in long days. In addition, alleles of Hd1 account for ~ 44% of the variation in flowering time observed in cultivated rice and sorghum. How does it work in bamboo? The function of CO in bamboo is similar to that in Arabidopsis ? Results Two CO homologous genes, PvCO1 and PvCO2 , in Phyllostachys violascens were identified. Alignment analysis showed that the two PvCOLs had the highest sequence similarity to rice Hd1. Both PvCO1 and PvCO2 expressed in specific tissues, mainly in leaf. The PvCO1 gene had low expression before flowering, high expression during the flowering stage, and then declined to low expression again after flowering. In contrast, expression of PvCO2 was low during the flowering stage, but rapidly increased to a high level after flowering. The mRNA levels of both PvCOs exhibited a diurnal rhythm. Both PvCO1 and PvCO2 proteins were localized in nucleus of cells. PvCO1 could interact with PvGF14c protein which belonged to 14–3-3 gene family through B-box domain. Overexpression of PvCO1 in Arabidopsis significantly caused late flowering by reducing the expression of AtFT , whereas, transgenic plants overexpressing PvCO2 showed a similar flowering time with WT under LD conditions. Taken together, these results suggested that PvCO1 was involved in the flowering regulation, and PvCO2 may either not have a role in regulating flowering or act redundantly with other flowering regulators in Arabidopsis . Our data also indicated regulatory divergence between PvCOLs in Ph. violascens and CO in Arabidopsis as well as Hd1 in Oryza sativa. Our results will provide useful information for elucidating the regulatory mechanism of COLs involved in the flowering. Conclusions Unlike to the CO gene in Arabidopsis , PvCO1 was a negative regulator of flowering in transgenic Arabidopsis under LD condition. It was likely that long period of vegetative growth of this bamboo species was related with the regulation of PvCO1.

CONSTANS (CO)/CONSTANS-like (COL) genes play an important role in the photoperiodic flowering pathway. However, the functional roles of the CO/COL genes in mango (Mangifera indica L.) remain unknown. In this study, the MiCO gene was isolated from mango and functionally characterized. The open reading frame is 966 bp in length and encodes 322 amino acids; the protein contains two conserved B-box zinc finger domains and a CCT domain and thus belongs to the CO/COL group I protein family. The MiCO protein fused to green fluorescent protein localized to the nucleus. MiCO was expressed in all tested organs and was highly expressed especially in the leaves and stems of nonflowering branches, but its expression decreased in flowering branches. The expression level of MiCO significantly increased during the transition from vegetative to reproductive growth. MiCO was also expressed in accordance with the circadian rhythm, with the greatest expression level detected at 09:00. Overexpression of MiCO in Arabidopsis significantly delayed flowering under both long-day and short-day conditions.Key messageIn this study, a MiCO gene from mango was characterized. Overexpression of MiCO delayed flowering in transgenic Arabidopsis. The MiCO gene may play an important role in the flowering process of mango.