Browsing by Subject "Gerbera hybrida"

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  • Hadid, Feras (Helsingin yliopisto, 2021)
    The growing demand for crop products caused by population growth and climate change encourages plant scientists to investigate sustainable strategies to tackle such problems. Translating the knowledge of plant molecular mechanisms into applicable practices in the field would help in improving the plants' efficiency and productivity. The size of a plant's shoot apical meristem (SAM) is an important factor in biomass production and crop productivity. Besides, understanding the molecular regulation of the shoot apical meristem would help to know more about the 3D growth innovations of different plant families across the kingdom. This thesis aimed to study the regulation mechanisms of the meristem activity in Gerbera, the model organism of the Asteraceae family that has an informative phylogenetic position to understand evolutionary events. The inflorescence of Gerbera is highly resembling clv3 mutants in Arabidopsis. CLV3 peptide is involved in maintaining the meristem activity, these differences between the two species suggested an evolutionary modification for this pathway. GhCLV3-GhWUS signaling components in Gerbera hybrida were identified following bioinformatics approaches. Then sequence comparisons and phylogenetic analyses between Gerbera sequences and other species were performed. The coding sequence of GhCLV1 was cloned to expression vectors. The expression pattern analysis of the receptors was performed by RT-PCR and RNA-seq data. The results suggest that GhCLV1 is an important factor in maintaining the enlarged inflorescence meristem in Gerbera. Also, all the other receptors were expressed at different levels suggesting their contribution in the GhCLV3-GhWUS pathway and inflorescence termination.
  • Kontturi, Juha; Osama, Raisa; Deng, Xianbao; Bashandy, Hany; Albert, Victor A.; Teeri, Teemu H. (2017)
    The chalcone synthase superfamily consists of type III polyketidesynthases (PKSs), enzymes responsible for producing plant secondary metabolites with various biological and pharmacological activities. Anther-specific chalcone synthase-like enzymes (ASCLs) represent an ancient group of type III PKSs involved in the biosynthesis of sporopollenin, the main component of the exine layer of moss spores and mature pollen grains of seed plants. In the latter, ASCL proteins are localized in the tapetal cells of the anther where they participate in sporopollenin biosynthesis and exine formation within the locule. It is thought that the enzymes responsible for sporopollenin biosynthesis are highly conserved, and thus far, each angiosperm species with a genome sequenced has possessed two ASCL genes, which in Arabidopsis thaliana are PKSA and PKSB. The Gerbera hybrida (gerbera) PKS protein family consists of three chalcone synthases (GCHS1, GCHS3 and GCHS4) and three 2-pyrone synthases (G2PS1, G2PS2 and G2PS3). In previous studies we have demonstrated the functions of chalcone synthases in flavonoid biosynthesis, and the involvement of 2-pyrone synthases in the biosynthesis of antimicrobial compounds found in gerbera. In this study we expanded the gerbera PKS-family by functionally characterizing two gerbera ASCL proteins. In vitro enzymatic studies using purified recombinant proteins showed that both GASCL1 and GASCL2 were able to use medium and long-chain acyl-CoA starters and perform two to three condensation reactions of malonyl-CoA to produce tri- and tetraketide 2-pyrones, usually referred to as alpha-pyrones in sporopollenin literature. Both GASCL1 and GASCL2 genes were expressed only floral organs, with most expression observed in anthers. In the anthers, transcripts of both genes showed strict tapetum-specific localization. (C) 2016 Elsevier Ltd. All rights reserved.
  • Zhao, Yafei (Helsingfors universitet, 2013)
    The transition from vegetative growth to flower formation is especially crucial for the reproduction of flowering plants. This transition is controlled through the regulatory activities of a group of genes named as floral meristem identity genes, of which LEAFY (LFY) is thought as the most important one. As a plant-specific transcription factor, LFY controls flower formation and floral patterning, which has been most intensively studied in the model annual plant Arabidopsis. In contrast to the plant architecture and flower morphology in Arabidopsis, Gerbera (Gerbera hybrida), belonging to the large sunflower family (Asteraceae), processes head-like inflorescences with different types of flowers distinct in floral morphs, sex and sometimes coloration. Within the last decades, a number of MADS-box and TCP transcription factor genes have been functionally characterized using stable transgenic plants. Recently, another functional assessment method using virus-induced gene silencing (VIGS) has been developed in Gerbera hybrida. In this study, the expression pattern of GhLFY was analyzed in wild-type Gerbera and TRV-based GhLFY silencing was conducted in two Gerbera cultivars – Terra Regina and Grizzly. It could be concluded that the activity of GhLFY is involved in regulating flower development. In VIGS:GhLFY lines, leaf-like organs emerged in disc flowers and the identity of stamen and carpel was interrupted. However, further VIGS trials are needed verify the observed phenotypes. At the same time, two potential lfy mutants – Pingpong and Marimbo were analyzed in both phenotype and genotype. These cultivars show phenotypic alteration in inflorescence development and floral organ structures that were distinct from WT Gerbera. Although the expression level of GhLFY did not change among these cultivars, but the GhLFY sequences contained amino acids mutation sites and four missing proline amino acids in Marimbo were detected. The role of these mutation sites need to be further analyzed in later experimental steps.
  • Juntheikki-Palovaara, Inka; Tahtiharju, Sari; Lan, Tianying; Broholm, Suvi K.; Rijpkema, Anneke S.; Ruonala, Raili; Kale, Liga; Albert, Victor A.; Teeri, Teemu H.; Elomaa, Paula (2014)
  • Pöllänen, Eija (University of Helsinki, 2000)
  • Osama, Raisa (Helsingfors universitet, 2016)
    The polyketide synthases (PKSs) are a large group of enzymes that catalyze the decarboxylative condensation of malonyl-CoA with various CoA thioesters, in order to biosynthesize different plant secondary metabolites. Anther specific chalcone synthase like (ASCL) enzymes are a novel group of plant type III polyketide synthase involved in the biosynthesis of sporopollenin, which is the stable biopolymer present in the exine layer of pollen walls. A gene encoding polyketide synthase, GhPKS8, was isolated from Gerbera hybrida from RNA sequencing data using gene specific primers. The structure, expression pattern and enzymatic activity of the corresponding enzyme were analyzed. The expression studies revealed that the GhPKS8 transcript is expressed at an early phase of anther development. Sequence analysis showed that the gerbera GhPKS8 gene displayed a high level (79%) of similarity to AtPKSB, the ASCL gene of Arabidopsis thaliana and all the important residues were seen to be conserved in the deduced amino acid sequence of GhPKS8. Additionally, the catalytic properties showed that the enzyme accepts medium chain starter as a substrate. The sequence homology, expression studies together with enzymatic assays revealed that the gerbera GhPKS8 may be an ASCL, involved in the development of anther. The putative role of GhPKS8 in anther exine development is discussed.