Browsing by Author "Zhang, Yao"

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  • Zhang, Yao (Helsingfors universitet, 2012)
    The evolution of floral novelties involves activities of several transcription factors. The large Asteraceae plant family has inflorescences consisting of different types of flowers. TCP transcription factors have recently been reported to regulate this complex structure. Gerbera hybrida, a common ornamental crop, has been used as a model plant for flower developmental studies in Asteraceae. It can be genetically transformed; however, transformation is laborious and time-consuming. Calendula officinalis also belongs to the Asteraceae plant family. It has working micropropagation methods, and it grows and flowers faster than Gerbera hybrida. In addition, Calendula officinalis genes possess high sequence similarity to Gerbera hybrida genes and thus provide an opportunity for functional testing of large numbers of genes. For functional assessment, virus induced gene silencing (VIGS) is a rapid approach, as it circumvents the need to establish stable transgenic lines that requires efficient tissue culture and time-consuming whole-plant regeneration steps. In this study, twelve Calendula officinalis cultivars were tested for VIGS. Calendula showed potential as a new model for the Asteraceae plant family as all twelve different cultivars could be infected by tobacco rattle virus (TRV) via observing the fluorescence caused by pTRV2: GFP; and they all showed photobleaching silencing phenotype caused by PHYTOENE DESATURASE (GhPDS) gene from gerbera. Especially the cultivars „Touch of Red/Orange? and „Princess Orange? turned out to be the most efficient in silencing. Virus dynamics was successfully traced by fluorescence encoded by pTRV2: GFP construct. However, using the construct pTRV2: GFP: PDS, it was observed that the GFP gene could not be applied as a marker gene to indicate the silencing area, because fluorescence could not be observed in photobleaching area. The calendula PDS was also tested. More similar sequence corresponding to the plant?s endogenous gene could cause more visible silencing symptom, but quantitative polymerase chain reaction results showed no statistically significant difference on gene silencing efficiency between GhPDS and CoPDS fragments. VIGS was also tested for silencing of TCP domain transcription factor genes using gerbera specific gene fragments. It was observed that the VIGS approach was not suitable for functional testing of CYCLOIDEA-clade genes in Calendula officinalis as identification of the putative phenotypes was highly disturbed by variable inflorescence phenotype of the tested cultivar.