SOC1-like Genes Research Articles

Over-expression of the Gerbera hybrida At-SOC1-like1 gene Gh-SOC1 leads to floral organ identity deterioration.

The family of MADS box genes is involved in a number of processes besides controlling floral development. In addition to supplying homeotic functions defined by the ABC model, they influence flowering time and transformation of vegetative meristem into inflorescence meristem, and have functions in roots and leaves. Three Gerbera hybrida At-SOC1-like genes (Gh-SOC1-Gh-SOC3) were identified among gerbera expressed sequence tags. Evolutionary relationships between SOC1-like genes from gerbera and other plants were studied by phylogenetic analysis. The function of the gerbera gene Gh-SOC1 in gerbera floral development was studied using expression analysis, protein-protein interaction assays and reverse genetics. Transgenic gerbera lines over-expressing or downregulated for Gh-SOC1 were obtained using Agrobacterium transformation and investigated for their floral phenotype. Phylogenetic analysis revealed that the closest paralogues of At-SOC1 are Gh-SOC2 and Gh-SOC3. Gh-SOC1 is a more distantly related paralogue, grouping together with a number of other At-SOC1 paralogues from arabidopsis and other plant species. Gh-SOC1 is inflorescence abundant and no expression was seen in vegetative parts of the plant. Ectopic expression of Gh-SOC1 did not promote flowering, but disturbed the development of floral organs. The epidermal cells of ray flower petals appeared shorter and their shape was altered. The colour of ray flower petals differed from that of the wild-type petals by being darker red on the adaxial side and greenish on the abaxial surface. Several protein-protein interactions with other gerbera MADS domain proteins were identified. The At-SOC1 paralogue in gerbera shows a floral abundant expression pattern. A late petal expression might indicate a role in the final stages of flower development. Over-expression of Gh-SOC1 led to partial loss of floral identity, but did not affect flowering time. Lines where Gh-SOC1 was downregulated did not show a phenotype. Several gerbera MADS domain proteins interacted with Gh-SOC1.

Characterization of FLC, SOC1 and FT homologs in Eustoma grandiflorum: effects of vernalization and post‐vernalization conditions on flowering and gene expression

A rosette plant of Eustoma grandiflorum requires vernalization (exposure to a period of cold temperature) and long-day conditions to promote flowering, while prolonged cold or cool temperatures in post-vernalization periods delay flowering. This study aimed to investigate the effect of growth conditions on flowering regulation in Eustoma. In Arabidopsis, vernalization suppresses a floral repressor gene, FLOWERING LOCUS C (FLC) and upregulates floral promoter genes, such as SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and FLOWERING LOCUS T (FT). We identified and characterized the Eustoma homologs of these genes. In contrast to Arabidopsis FLC, Eustoma grandiflorum FLC-like (EgFLCL) expression was upregulated by cold temperature and downregulated by subsequent warm temperature exposure. The expression of Eustoma grandiflorum SOC1-like (EgSOC1L) and FT-like (EgFTL) genes was not significantly induced during vernalization, but their transcripts increased during a warm post-vernalization period in the long days. Vernalized plants grown under cool post-vernalization temperatures exhibited higher EgFLCL expression, lower EgSOC1L and EgFTL expression and flowered later than those grown under warm temperatures. Overexpression of EgFLCL cDNA repressed flowering in transgenic Arabidopsis, whereas overexpression of EgSOC1L or EgFTL cDNA promoted flowering. Our results suggest that flowering regulation by vernalization in Eustoma differs from the paradigm developed for Arabidopsis. EgFLCL is regulated by temperature and may be involved in floral repression during cold and cool seasons. Warm- and long-day conditions following vernalization are required to induce two putative floral promoters, EgSOC1L and EgFTL, effectively.

Overexpression of Petunia SOC1-like Gene FBP21 in Tobacco Promotes Flowering Without Decreasing Flower or Fruit Quantity

FBP21 is one of the SOC1-like genes isolated from Petunia hybrida. Based on sequence analysis, FPB21 is suggested to have a role in promoting flowering. In this study, FBP21 was expressed in a tobacco host plant under the control of the CaMV 35S promoter. Our results showed that the transgene accelerated flowering, i.e. the transgenic plants flowered just 3 months after germination, in comparison to the wild-type tobacco which flowered after 5 months. Plant morphology was also affected, with the transgenic tobacco plants developing at least five robust lateral branches, while the control plants generally had just three. Total leaf area was significantly reduced in the transgenic tobacco compared to wild-type tobacco. By contrast, there was no significant difference between transgenic and control plants for the total number of flowers or fruits. Thus, the flower or fruit yield expressed per unit leaf area was higher in transgenic tobacco than in wild-type plants. Semi-quantitative RT-PCR analysis indicated that overexpression of FBP21 in tobacco resulted in the up-regulation of some flowering-related genes. The results of this study in tobacco indicate that the Petunia FBP21 gene may permit the engineering of early-flowering and short-growth habits without compromising flower or fruit yields.

Functional characterization of AP3, SOC1 and WUS homologues from citrus (Citrus sinensis)

Flowering and flower formation are defining features of angiosperms and the control of these developmental processes involves a common repertoire of genes which are shared among different species of flowering plants. These genes were first identified using various homeotic and flowering time mutants of Arabidopsis and snapdragon, and homologous genes have subsequently been isolated from a wide range of different plant species based on the conservation of protein sequence and function. Using degenerate reverse-transcriptase polymerase chain reaction, we have isolated one APETALA3-like (CitMADS8) and two SOC1 (SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1)-like (CsSL1 and CsSL2) homologues from sweet orange (Citrus sinensis L.). Although the translated amino acid sequence of CitMADS8 shares many similarities with other higher plant APETALA3 proteins, CitMADS8 fails to complement the floral organ identity defects of the Arabidopsis ap3-3 mutant. By contrast, the two citrus SOC1-like genes, particularly CsSL1, are able to shorten the time taken to flower in the Arabidopsis wild-type ecotypes Columbia and C24, and functionally complement the late flowering phenotype of the soc1 mutant, essentially performing the endogenous function of Arabidopsis SOC1. Once flowering has commenced, interactions between specific flowering genes and a gene required for meristem maintenance, WUSCHEL, ensure that the Arabidopsis flower is a determinate structure with four whorls. We have isolated a citrus WUSCHEL homologue (CsWUS) that is capable of restoring most of the meristem function to the shoots and flowers of the Arabidopsis wus-1 mutant, implying that CsWUS is the functional equivalent of Arabidopsis WUSCHEL.

Eucalyptus grandis has at least two functional SOC1-like floral activator genes.

In a search for Eucalyptus grandis Hill ex Maiden MADS-box genes involved in floral initiation and development, we isolated two cDNAs (EgrMADS 3 and EgrMADS 4), which are functional orthologues of the Arabidopsis thaliana (L.) Heynh. floral activator gene SOC1. These two E. grandis genes are equally and most-actively expressed in vegetative tissues such as apical shoots and young leaves. The two genes are less actively, but differentially expressed in roots and unopened flowers. Ectopic expression of EgrMADS 3 or EgrMADS 4 in the late-flowering A. thaliana Ler soc1 (agl20) derivative complemented the phenotype of this mutant, and some of these transgenic lines flowered significantly earlier than the wild-type Ler ecotype. Overexpression of EgrMADS 3 or EgrMADS 4 in A. thaliana ecotype Columbia accelerated flowering time under short-day conditions. However, under the same conditions the flowering time of A. thaliana ecotype C24 was altered by the ectopic expression of EgrMADS 3, but not that of EgrMADS 4.The nucleotide sequence data reported will appear in the EMBL and GenBank Nucleotide Databases under the accession numbers AY263807 (EgrMADS 3) and AY263808 (EgrMADS 4).