Functional and Evolutionary Characterization of the CONSTANS-like Family in Lilium�formolongi

MiCOL6, MiCOL7A and MiCOL7B isolated from mango regulate flowering and stress response in transgenic Arabidopsis

The CONSTANS/CONSTANS-Like (CO/COL) family has been shown to play important roles in flowering, stress tolerance, fruit development and ripening in higher plants. In this study, three COL genes, MiCOL6, MiCOL7A and MiCOL7B, which each contain only one CCT domain, were isolated from mango (Mangifera indica), and their functions were investigated. MiCOL7A and MiCOL7B were expressed mainly at 20 days after flowering (DAF), and all three genes were highly expressed during the flowering induction period. The expression levels of the three genes were affected by light conditions, but only MiCOL6 exhibited a clear circadian rhythm. Overexpression of MiCOL6 promoted earlier flowering, while overexpression of MiCOL7A or MiCOL7B delayed flowering compared to that in the control lines of Arabidopsis thaliana under long-day (LD) and short-day (SD) conditions. Overexpressing MiCOL6, MiCOL7A or MiCOL7B in transgenic plants increased superoxide dismutase (SOD) and proline levels, decreased malondialdehyde (MAD) levels, and improved survival under drought and salt stress. In addition, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses showed that the MiCOL6, MiCOL7A and MiCOL7B proteins interact with several stress- and flower-related proteins. This work demonstrates the functions of MiCOL6, MiCOL7A and MiCOL7B and provides a foundation for further research on the role of mango COL genes in flowering regulation and the abiotic stress response.

Functional analysis of a lily SHORT VEGETATIVE PHASE ortholog in flowering transition and floral development

Lilium is a commercially important genus of bulbous flowers, investigating the flowering molecular mechanisms is important for flowering regulation of lily. MADS-box SHORT VEGETATIVE PHASE (SVP) orthologs are involved in the flowering transition and floral organ differentiation in many plants. In this study, we identified an SVP ortholog from L. × formolongi (LfSVP), which was closely related to Arabidopsis SVP according to phylogenetic analysis. Tissue-specific expression patterns indicated that LfSVP expression levels peaked in the leaves and showed low expression levels in flowering tepals. Stage-dependent expression patterns of LfSVP showed high transcription level in the flowering induction stage under different photoperiods and exhibited transcription peak in the floral budding development stage under long days. Overexpressed LfSVP led to delayed flowering and floral organ defects in Arabidopsis independent of photoperiod. Tobacco rattle virus -induced gene silencing of LfSVP caused a strongly earlier flowering time and floral organ defects of L. × formolongi. Moreover, LfSVP can interact with L. × formolongi APETALA1 (AP1) in both yeast and tobacco cells, and the two may interact to regulate floral organ differentiation. In conclusion, LfSVP is a flowering repressor and may be involved in the regulation of floral organ differentiation. This study will be helpful for the molecular breeding of short-life-period and rich floral patterns lily varieties.

Identification of the CONSTANS-like family in Cymbidium sinense, and their functional characterization

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.

Transcriptomics reveals the molecular mechanisms of flesh colour differences in eggplant (Solanum melongena)

BACKGROUND

Fruit flesh colour is not only an important commodity attribute of eggplant but is also closely related to maturity. However, very little is known about its formation mechanism in eggplant.

RESULTS

Two inbred lines of eggplant, green 'NC7' and white 'BL', were used in this study to explain the differences in flesh colour. Transcriptome sequencing results revealed a total of 3304 differentially expressed genes (DEGs) in NC7 vs. BL. Of the DEGs obtained, 2050 were higher and 1254 were lower in BL. These DEGs were annotated to 126 pathways, where porphyrin and chlorophyll metabolism, flavonoid biosynthesis, and photosynthesis-antenna proteins play vital roles in the colour formation of eggplant flesh. At the same time, Gene Ontology (GO) enrichment significance analysis showed that a large number of unigenes involved in the formation of chloroplast structure were lower in BL, which indicated that the formation of chloroplasts in white-fleshed eggplant was blocked. This was confirmed by transmission electron microscopy (TEM), which found only leucoplasts but no chloroplasts in the flesh cells of white-fleshed eggplant. Several genes encoding ERF and bHLH transcription factors were predicted to participate in the regulation of chlorophyll biosynthetic genes.

CONCLUSIONS

The results of this study indicated that differences in the gene expression of the chlorophyll metabolic pathway were the main cause of the different flesh colour formations. These findings will increase our understanding of the genetic basis in eggplant flesh colors formation mechanism.

Genome-wide identification of the mango CONSTANS (CO) family and functional analysis of two MiCOL9 genes in transgenic Arabidopsis

CONSTANS/CONSTANS-like (CO/COL) transcription factors play a vital role in the photoperiodic flowering pathway. However, the biological functions of COL genes in mango are unclear. In this study, we identified 31 COL genes from the 'Jin Huang' mango genome and divided them into three groups according to the specific gene structure and protein domain characteristics. These 31 MiCOL genes were heterogeneously distributed on 14 chromosomes. Expression pattern analysis showed that most MiCOL genes were mainly expressed in leaves and stems and during the floral induction period, followed by the floral differentiation period. The expression of COL genes was induced by drought and salt stress, but the expression patterns of different genes were different, which may suggest that MiCOL genes are involved in the abiotic stress response of mango. Under salt and drought conditions, two MiCOL9 genes can improve the resistance of Arabidopsis by improving the scavenging ability of ROS and proline accumulation and reducing the MDA content. Additionally, overexpression of MiCOL9 genes significantly inhibited flowering in transgenic Arabidopsis. This work provides an important foundation for understanding the biological roles of mango COL genes in plant growth, development and stress responses.

Expression Patterns of Key Genes in the Photoperiod and Vernalization Flowering Pathways in Lilium longiflorum with Different Bulb Sizes

Lilium longiflorum is a wild Lilium, and its flowering transition requires a long period of cold exposure to meet the demand of vernalization. The responses of different sized bulbs to cold exposure and photoperiod are different, and the floral transition pathways of small and large bulbs are different. In this study, small and large bulbs were placed in cold storage for different weeks and then cultured at a constant ambient temperature of 25 °C under long day (LD) and short day (SD) conditions. Then, the flowering characteristics and expression patterns of key genes related to the vernalization and photoperiod pathways in different groups were calculated and analyzed. The results showed that the floral transition of Lilium longiflorum was influenced by both vernalization and photoperiod, that vernalization and LD conditions can significantly improve the flowering rate of Lilium longiflorum, and that the time from planting to visible flowering buds’ appearance was decreased. The flowering time and rate of large bulbs were greatly influenced by cold exposure, and the vernalization pathway acted more actively at the floral transition stage. The floral transition of small bulbs was affected more by the photoperiod pathway. Moreover, it was speculated that cold exposure may promote greater sensitivity of the small bulbs to LD conditions. In addition, the expression of LlVRN1, LlFKF1, LlGI, LlCO5, LlCO7, LlCO16, LlFT1, LlFT3 and LlSOC1 was high during the process of floral transition, and LlCO13, LlCO14 and LlCO15 were highly expressed in the vegetative stage. The expression of LlCO13 and LlCO14 was different under different lighting conditions, and the flowering induction function of LlCO9 and LlFT3 was related to vernalization. Moreover, LlFKF1, LlGI, LlCO5, LlCO16, LlSOC1 and LlFT2 were involved in the entire growth process of plants, while LlCO6, LlCO16 and LlFT1 are involved in the differentiation and formation of small bulblets of plants after the inflorescence stage, and this process is also closely related to LD conditions. This study has great significance for understanding the molecular mechanisms of the vernalization and photoperiod flowering pathways of Lilium longiflorum.

Transcriptome Analysis of Lycoris chinensis Bulbs Reveals Flowering in the Age-Mediated Pathway

Lycoris is a summer bulbous flower that commonly needs to go through a long period of vegetative growth for 3 to 5 years before flowering. Plant flowering is regulated by a complex genetic network. Compared with most perennial flowers, knowledge on the molecular mechanism responsible for floral transition in bulbous flowers is lacking, and only a few genes that regulate flowering have been identified with few reports on the floral transition in Lycoris. In this study, we identified many differentially expressed genes (DEGs) and transcription factors (TFs) by RNA-Seq in L. chinensis bulbs of different ages, including one- to four-year-old nonflowering bulbs and four-year-old flowering bulbs. Some DEGs were enriched in Gene Ontology (GO) terms between the three- and four-year-old bulbs, and there most genes were enriched in terms of metabolic process and catalytic activity. In the four-year old bulbs, most of the DEGs that may be involved in flowering were classified under the GO term biological process, which was a totally different result from the vegetative bulbs. Some DEGs between flowering and nonflowering bulbs were enriched in plant hormone signal transduction, including the hormones auxin, cytokinin, abscisic acid, and ethylene, but no DEGs were enriched in the gibberellin pathway. Auxin is the main endogenous phytohormone involved in bulb growth and development, but cytokinin, abscisic acid, and ethylene were shown to increase in flowering bulbs. In addition, energy-metabolism-related genes maintain a high expression level in large bulbs, and some positive regulators (SPL, COL, and AP1) and early flowering genes were also shown to be highly expressed in the meristems of flowering bulbs. It suggested that sugar molecules may be the energy source that regulates the signal transduction of flowering by connecting with phytohormone signaling in Lycoris. A total of 1911 TFs were identified and classified into 89 categories, where the top six families with the largest gene numbers were C2H2, NAC, AP2/ERF-ERF, C3H, MYB-related, and WRKY. Most DEGs were in the AP2/ERF-ERF family, and most of them were downregulated in 4-year-old flowering bulbs. A number of families were reported to be involved in plant flowering, including NAC, AP2/ERF, MYB, WRKY, bZIP, MADS, and NF-Y. These results can act as a genetic resource to aid in the explanation of the genetic mechanism responsible for the flowering of Lycoris and other bulbous flowers.

Molecular cloning of cryptochrome 1 from Lilium×formolongi and the characterization of its photoperiodic flowering function in Arabidopsis

Lilium × formolongi is an important cut flower species that is able to flower within a year following seed propagation, with flower induction that is very sensitive to the photoperiod. Cryptochromes are blue/UV-A light receptors that regulate many important plant growth and development processes, including photoperiodic flowering. In this study, we isolated the cryptochrome 1 (CRY1) gene from L. × formolongi and analyzed its function in transgenic Arabidopsis. The predicted LfCRY1 protein was strongly homologous to other CRY1 proteins. The transcription of LfCRY1 was induced by blue light, with LfCRY1 exhibiting its highest expression and diurnal expression patterns during the flowering-induction stage under both long-day (LD) and short-day (SD) photoperiods. Overexpression of LfCRY1 in Arabidopsis promoted flowering under LDs but not SDs and inhibited hypocotyl elongation under blue light. The LfCRY1 protein was located in both the nucleus and cytoplasm. LfCRY1 interacted with the important flowering activator LfCOL9 in both yeast and onion cells. These results provide functional evidence for the role of LfCRY1 in controlling photoperiodic flowering under LDs and indicate that LfCRY1 may be a counterpart of AtCRY1. Understanding the role of LfCRY1 in photoperiodic flowering is beneficial for the molecular breeding of lilies with shorter vegetative stages.

Genome-wide analysis of the CCT gene family in Chinese white pear (Pyrus bretschneideri Rehd.) and characterization of PbPRR2 in response to varying light signals

BACKGROUND

Canopy architecture is critical in determining the light environment and subsequently the photosynthetic productivity of fruit crops. Numerous CCT domain-containing genes are crucial for plant adaptive responses to diverse environmental cues. Two CCT genes, the orthologues of AtPRR5 in pear, have been reported to be strongly correlated with photosynthetic performance under distinct canopy microclimates. However, knowledge concerning the specific expression patterns and roles of pear CCT family genes (PbCCTs) remains very limited. The key roles played by PbCCTs in the light response led us to examine this large gene family in more detail.

RESULTS

Genome-wide sequence analysis identified 42 putative PbCCTs in the genome of pear (Pyrus bretschneideri Rehd.). Phylogenetic analysis indicated that these genes were divided into five subfamilies, namely, COL (14 members), PRR (8 members), ZIM (6 members), TCR1 (6 members) and ASML2 (8 members). Analysis of exon-intron structures and conserved domains provided support for the classification. Genome duplication analysis indicated that whole-genome duplication/segmental duplication events played a crucial role in the expansion of the CCT family in pear and that the CCT family evolved under the effect of purifying selection. Expression profiles exhibited diverse expression patterns of PbCCTs in various tissues and in response to varying light signals. Additionally, transient overexpression of PbPRR2 in tobacco leaves resulted in inhibition of photosynthetic performance, suggesting its possible involvement in the repression of photosynthesis.

CONCLUSIONS

This study provides a comprehensive analysis of the CCT gene family in pear and will facilitate further functional investigations of PbCCTs to uncover their biological roles in the light response.

Identification of trehalose-6-phosphate synthase (TPS)-coding genes involved in flowering induction of Lilium× formolongi

Lilium × formolongi, a facultative long-day (LD) plant, can complete the floral transition within one year after sowing under LD conditions. In addition to the photoperiod, the molecular mechanisms by which other flowering regulators, such as sugar, participate in juvenile development and flowering induction in L. × formolongi remain elusive. Therefore, based on the investigation of seedling development under different day length conditions, we explored the growth and nonstructural carbohydrate (NSC) contents of leaves and underground bulbs. Furthermore, the expression profiles of trehalose-6-phosphate synthase (TPS)-coding genes, LfTPSs, and miR156 were also determined. Three putative LfTPS genes, LfTPS1, LfTPS3 and LfTPS5, displayed high expression levels at the juvenile vegetative stage under different day length conditions. Among them, LfTPS1 maintained gradually elevated expression until the visible bud stage under short-day (SD) conditions. Additionally, the expression levels of LfTPS3 and LfTPS5 increased with the exogenous sucrose concentration. In contrast, the expression of miR156 rapidly decreased under the same sucrose treatments. Overexpression of LfTPS1/3/5 hastened flowering and the decline in miR156 expression levels to varying degrees in transgenic Arabidopsis. Taken together, the results demonstrate that LfTPS1, LfTPS3 and LfTPS5 modulate both juvenile vegetative development and flowering induction controlled by sugars in L. × formolongi.

Cryptochrome 2 from Lilium × formolongi Regulates Photoperiodic Flowering in Transgenic Arabidopsis thaliana

The photoperiodic flowering pathway is essential for plant reproduction. As blue and ultraviolet-A light receptors, cryptochromes play an important role in the photoperiodic regulation of flowering. Lilium × formolongi is an important cut flower that flowers within a year after seed propagation. Floral induction is highly sensitive to photoperiod. In this study, we isolated the CRYPTOCHROME2 gene (LfCRY2) from L. × formolongi. The predicted LfCRY2 protein was highly homologous to other CRY2 proteins. The transcription of LfCRY2 was induced by blue light. LfCRY2 exhibits its highest diurnal expression during the floral induction stage under both long-day and short-day photoperiods. Overexpression of LfCRY2 in Arabidopsis thaliana promoted flowering under long days but not short days, and inhibited hypocotyl elongation under blue light. Furthermore, LfCRY2 was located in the nucleus and could interact with L. × formolongi CONSTANS-like 9 (LfCOL9) and A. thaliana CRY-interacting basic-helix-loop-helix 1 (AtCIB1) in both yeast and onion cells, which supports the hypothesis that LfCRY2 hastens the floral transition via the CIB1-CO pathway in a manner similar to AtCRY2. These results provide evidence that LfCRY2 plays a vital role in promoting flowering under long days in L. × formolongi.

Functional analysis and expression patterns of members of the FLOWERING LOCUS T (FT) gene family in Lilium

Lilium is an important commercial flowering species, and there are many varieties and more than 100 species of wild Lilium. Lilium × formolongi is usually propagated from seedlings, and the flowering of these plants is driven mainly by the photoperiodic pathway. Most of the other lily plants are propagated via bulblets and need to be vernalized; these plants can be simply divided into pretransplantation types and posttransplantation types according to the time at which the floral transition occurs. We identified three Lilium FLOWERING LOCUS T (LFT) family members in 7 Lilium varieties, and for each gene, the coding sequence of the different varieties was identical. Among these genes, the LFT1 gene of Lilium was most homologous to the AtFT gene, which promotes flowering in Arabidopsis. We analyzed the expression patterns of LFT genes in Lilium × formolongi seedlings and in different Lilium varieties, and the results showed that LFT1 and LFT3 may promote floral induction. Compared with LFT3, LFT1 may have a greater effect on floral induction in Lilium, which is photoperiod sensitive, while LFT3 may play a more important role in the floral transition of lily plants, which have a high requirement for vernalization. LFT2 may be involved in the differentiation of bulblets, which was verified by tissue culture experiments, and LFT1 may have other functions involved in promoting bulblet growth. The functions of LFT genes were verified by the use of transgenic Arabidopsis thaliana plants, which showed that both the LFT1 and LFT3 genes can promote early flowering in Arabidopsis. Compared with LFT3, LFT1 promoted flowering more obviously, and thus, this gene could be an important promoter of floral induction in Lilium.

Analysis of miRNA-mediated regulation of flowering induction in Lilium × formolongi

BACKGROUND

MicroRNAs play pivotal roles in plant vegetative phase change and flowering induction via integrating into multiple flowering pathways. Lilium × formolongi is an important ornamental lily cultivar that can flower within one year after sowing. However, it remains unresolved how miRNA-mediated regulation networks contribute to the L. × formolongi characteristics of a short vegetative growth period and rapid flowering.

RESULTS

In this study, the small RNA libraries and one degradome library were constructed for L. × formolongi during vegetative growth and flowering initiation, and 366 conserved miRNAs and 32 novel miRNAs were identified. Additionally, 84 miRNAs were significantly differentially expressed during development. A total of 396 targets of 185 miRNAs were identified and validated through degradome sequencing. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that functions of the targets were top enriched in the cold and cadmium ion responses, pentose phosphate pathway and carbon fixation in photosynthetic organisms. Furthermore, among 23 differentially expressed miRNA-target pairs, the miR156s-LfSPL2, miR172a-LfAP2 and miR164a-LfNAC pairs as well as miR159a-LfSPL2 were found to be relevant to flowering based on the correlation analysis of expression profiles in the miRNA libraries, degradome and transcriptome. A coexpression regulatory network focused on differentially expressed pairs was also constructed by WGCNA, and 14 miRNAs were considered putative key miRNAs during vegetative development and flowering induction. miR156a/ d/ e showed particularly strong relationships with other miRNAs in the coexpression network.

CONCLUSIONS

This study provides cues for the further exploration of the regulatory mechanisms of short vegetative development and flowering in L. × formolongi.

Genome-wide identification, expression, and sequence analysis of CONSTANS-like gene family in cannabis reveals a potential role in plant flowering time regulation

BACKGROUND

Cannabis, an important industrial crop, has a high sensitivity to photoperiods. The flowering time of cannabis is one of its important agronomic traits, and has a significant effect on its yield and quality. The CONSTANS-like (COL) gene plays a key role in the regulation of flowering in this plant. However, the specific roles of the COL gene family in cannabis are still unknown.

RESULTS

In this study, 13 CsCOL genes were identified in the cannabis genome. Phylogenetic analysis implied that the CsCOL proteins were divided into three subgroups, and each subgroup included conserved intron/exon structures and motifs. Chromosome distribution analysis showed that 13 CsCOL genes were unevenly distributed on 7 chromosomes, with chromosome 10 having the most CsCOL members. Collinearity analysis showed that two syntenic gene pairs of CsCOL4 and CsCOL11 were found in both rice and Gossypium raimondii. Of the 13 CsCOL genes, CsCOL6 and CsCOL12 were a pair of tandem duplicated genes, whereas CsCOL8 and CsCOL11 may have resulted from segmental duplication. Furthermore, tissue-specific expression showed that 10 CsCOL genes were preferentially expressed in the leaves, 1 CsCOL in the stem, and 2 CsCOL in the female flower. Most CsCOL exhibited a diurnal oscillation pattern under different light treatment. Additionally, sequence analysis showed that CsCOL3 and CsCOL7 exhibited amino acid differences among the early-flowering and late flowering cultivars.

CONCLUSION

This study provided insight into the potential functions of CsCOL genes, and highlighted their roles in the regulation of flowering time in cannabis. Our results laid a foundation for the further elucidation of the functions of COL genes in cannabis.

Establishment of Efficient Genetic Transformation Systems and Application of CRISPR/Cas9 Genome Editing Technology in Lilium pumilum DC. Fisch. and Lilium longiflorum White Heaven

Lilium spp. is a bulb flower with worldwide distribution and unique underground organs. The lack of an efficient genetic transformation system for Lilium has been an international obstacle. Because existing model plants lack bulbs, bulb-related gene function verification studies cannot be carried out in model plants. Here, two stable and efficient genetic transformation systems based on somatic embryogenesis and adventitious bud regeneration were established in two Lilium species. Transgenic plants and T-DNA insertion lines were confirmed by β-glucuronidase (GUS) assay, polymerase chain reaction (PCR) and Southern blot. After condition optimization, transformation efficiencies were increased to 29.17% and 4% in Lilium pumilum DC. Fisch. and the Lilium longiflorum ‘White Heaven’, respectively. To further verify the validity of these transformation systems and apply the CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated protein 9) technology in Lilium, the LpPDS gene in the two Lilium species was knocked out. Completely albino, pale yellow and albino–green chimeric mutants were observed. Sequence analysis in the transgenic lines revealed various mutation patterns, including base insertion, deletion and substitution. These results verified the feasibility and high efficiency of both transformation systems and the successful application of the CRISPR/Cas9 system to gene editing in Lilium for the first time. Overall, this study lays an important foundation for gene function research and germplasm improvement in Lilium spp.

Overexpression of Lilium formosanumMADS-box (LFMADS) Causing Floral Defects While Promoting Flowering in Arabidopsis thaliana, Whereas Only Affecting Floral Transition Time in Nicotiana tabacum

The Formosa lily (Lilium formosanum) is one of the most common horticultural species in Taiwan. To explore gene regulation involved in this species, we used transcriptome analysis to generate PH-FB (mixed floral buds) and PH-LF (mature leaves) datasets. Combination of the PH-FB and PH-LF constructed a de novo assembly of the ALL dataset, including 18,041 contigs and 23,807 unigenes by Nr, GO, COG, and KEGG databases. The differential gene expression (DGE) analysis revealed 9937 genes were upregulated while 10,383 genes were downregulated in the developing floral buds compared to mature leaves. Seven putative genes (LFMADS1 to 7) encoding floral organ identity proteins were selected for further analysis. LFMADS1-6 genes were specifically expressed in the floral organ, while LFMADS7 in the floral buds and mature leaves. Phylogenetic analysis revealed that LFMADS1-3 is classified into B-class, LFMADS4 into C-class, LFMADS5 into D-class, and LFMADS6-7 into E-class, respectively. LFMADS-GFP fusion proteins appeared to localize in the nucleus, supporting their roles as transcription factors (TFs). Overexpression of the LFMADS2, LFMADS4, and LFMADS6 genes in Arabidopsis resulted in early flowering and floral defect, however, only early flowering in transgenic tobacco was observed. Highly expressed floral integrator genes, including AtFT, AtLFY, and AtFUL in transgenic Arabidopsis and NtFUL and NtSOC1 in transgenic tobacco, resulted in early flowering phenotype through qRT-PCR analysis. Yeast two-hybrid analysis suggested that LFMADSs may form higher order complexes with the B-, C-, D, and/or E-class proteins to determine the floral organ identity. Furthermore, E-class LFMADS proteins may function as a glue to mediate and strengthen the protein-protein interactions. Therefore, our de novo datasets would provide information for investigating other differentially expressed candidate transcripts. In addition, functional conservation of LFMADSs appears to be vital in floral transition and floral organ identity.