title: dsRNA silencing of an R2R3-MYB transcription factor affects flower cell shape in a Dendrobium hybrid.
abstract: BACKGROUND
  The R2R3-MYB genes regulate pigmentation and morphogenesis of flowers, including flower and cell shape, and therefore have importance in the development of new varieties of orchids. However, new variety development is limited by the long breeding time required in orchids. In this study, we identified a cDNA, DhMYB1, that is expressed during flower development in a hybrid orchid, Dendrobium hybrida (Dendrobium bobby messina X Dendrobium chao phraya) then used the direct application of dsRNA to observe the effect of gene silencing on flower phenotype and floral epidermal cell shape.
  
  
  RESULTS
  Flower bud development in the Dendrobium hybrid was characterised into seven stages and the time of meiosis was determined as between stages 3 to 5 when the bud is approximately half of the mature size. Scanning electron microscopy characterisation of adaxial epidermal cells of the flower perianth, showed that the petals and sepals each are divided into two distinct domains based on cell shape and size, while the labellum comprises seven domains. Thirty-two partial cDNA fragments representing R2R3-MYB gene sequences were isolated from D. hybrida. Phylogenetic analysis revealed that nine of the translated sequences were clustered with MYB sequences that are known to be involved in cell shape development and from these, DhMYB1 was selected for full length cDNA cloning and functional study. Direct application of a 430 bp dsRNA from the 3' region of DhMYB1 to emerging orchid flower buds reduced expression of DhMYB1 RNA compared with untreated control. Scanning electron microscopy of adaxial epidermal cells within domain one of the labellum of flowers treated with DhMYB1 dsRNA showed flattened epidermal cells whilst those of control flowers were conical.
  
  
  CONCLUSIONS
  DhMYB1 is expressed throughout flower bud development and is involved in the development of the conical cell shape of the epidermal cells of the Dendrobium hybrida flower labellum. The direct application of dsRNA changed the phenotype of floral cells, thus, this technique may have application in floriculture biotechnology.
authors.affiliation: Centre for Research in Biotechnology for Agriculture, University of Malaya, 50603, Kuala Lumpur, Malaysia. suee@um.edu.my.
authors.forename: Su-Ee
authors.initials: SE
authors.lastname: Lau
authors.affiliation: Department of Biology, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom. ts32@leicester.ac.uk.
authors.forename: Trude
authors.initials: T
authors.lastname: Schwarzacher
authors.affiliation: Centre for Research in Biotechnology for Agriculture, University of Malaya, 50603, Kuala Lumpur, Malaysia. yasmin@um.edu.my.|Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia. yasmin@um.edu.my.
authors.forename: Rofina Yasmin
authors.initials: RY
authors.lastname: Othman
authors.affiliation: Centre for Research in Biotechnology for Agriculture, University of Malaya, 50603, Kuala Lumpur, Malaysia. jennihari@um.edu.my.|Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia. jennihari@um.edu.my.
authors.forename: Jennifer Ann
authors.initials: JA
authors.lastname: Harikrishna
mesh_terms: D000595:Amino Acid Sequence; D048430:Cell Shape; D031667:Dendrobium / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D006824:Hybridization, Genetic; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D012330:RNA, Double-Stranded; D014157:Transcription Factors