Investigation into the role of R2R3-MYB transcription factors related to flower shape and colour in Dendrobium orchids / Muhammad Asyraf Khairul Anuar

Muhammad Asyraf , Khairul Anuar (2023) Investigation into the role of R2R3-MYB transcription factors related to flower shape and colour in Dendrobium orchids / Muhammad Asyraf Khairul Anuar. Masters thesis, Universiti Malaya.

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Abstract

During flower development, a set of structural genes are regulated to control the flower's colour and shape. R2R3-MYB transcription factors are important for controlling many different biological processes. However, we still don't know which members of this large family of transcription factors are involved in pigment and, in particular, organ shape development in a popular Dendrobium orchid with a dark purple flower. Phylogenetic analysis was used to find Dendrobium catenatum R2R3-MYB (DcaMYB) sequences that are likely to be involved in the development of pigment and cell shape. The expression of candidate DhMYB genes in Dendrobium hybrid was silenced by directly applying dsRNA to the developing flowers together with observation of the gene expression level and flower phenotypes. As a comparison, the structural pigment-related gene, chalcone synthase, was also silenced. Flowers treated with dsRNA of DhMYB22 and DhMYB60 sequences had less colour and low expression of anthocyanin biosynthesis genes (DFR and F3'H). They also had lower total anthocyanin and much lower cyanidin-3-glucoside and cyanidin-3-rutinoside content. The most significant difference in colour was seen in the petals of DhMYB22-treated flowers and the sepals of DhMYB60-treated flowers compared to the same organs of untreated flowers. The lips of flowers treated with hMYB22 were narrow and constricted, also observed in the sepals of flowers treated with DhMYB60. No significant difference was seen in the shape of flowers that were untreated or were treated with DhCHS. The results showed that Dendrobium's DhMYB22 and DhMYB60 control the amount of pigment and the shape of the flower organs. This is the first report that the shape of flower organs in orchids has been linked to MYB.

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