Working group session:
Functional Genomics
Presentation type:
oral
Authors:
Walford, Sally-Ann; Bedon, Frank; Tu, Lili; Llewellyn, Danny; Dennis, Elizabeth
Presenter:
Walford, Sally-Ann
Correspondent:
Walford, Sally-Ann
Abstract:
Cotton fibres are specialised epidermal cells that grow from the surface of the cotton seed. We have identified three regulatory genes that are important for instigating the development of these fibre cells - two R2-R3 MYBs (GhMYB25 and GhMYB25-like) and a homeodomain-leucine zipper protein (GhHD-1) GhMYB25-like and GhMYB25 belong to a unique MIXTA clade of MYB transcription factors involved in the regulation of cell morphogenesis in the petal epidermis. Another eight of these MIXTA MYBs have been found in the cotton genome sequence. They are all expressed during early fibre development. GhHD-1 is a member of the class IV HD-ZIP transcription factor family, known to be involved in the determination of epidermal cell type. RNAi-mediated suppression of GhHD-1 reduced trichome formation and delayed fibre initiation while constitutive over-expression of this gene increased the number of fibres initiating on the seed, but did not affect leaf trichomes. GhMYB25-silenced cotton exhibits delayed fibre initiation, shorter fibres and reduced trichomes on the plant, while over-expression of this gene increased fibre initiation and leaf trichome number. GhMYB25-like silenced plants produce fibreless seeds, but normal trichomes elsewhere. Constitutive over-expression of GhMYB25-like increased the number of fibre initials. Yeast two-hybrid and one-hybrid analysis and sequencing of RNA isolated from the outer integument of -4dpa, -2dpa and 0dpa wildtype ovules and 0dpa ovules from the silenced lines have identified additional proteins involved in the regulation of early fibre development. Based on our data we have developed a model of the genes and factors involved in the early stages of cotton fibre development.