Cotton fibres are differentiated single cells, originating from the epidermal layer of

the cotton ovule. Cotton fibre quality is determined by its length, strength and

fineness properties, which are largely controlled by genetic factors. Genes that are

expressed predominantly in fibre cells are likely to control development of the fibre

and contribute to these fibre characteristics.

The promoter sequence of the fibre-specific gene FSltp6 was isolated (Orford,

unpublished) and the region necessary for fibre-specific expression was identified

through successive 5’ deletions of the promoter (DELANEY 2005). An 84 bp region

identified, was subsequently used in a yeast-one-hybrid assay to identify transcription

factors that may regulate expression of FSltp6 (DELANEY 2005). Three classes of

novel cotton proteins were identified; HMGA-like proteins, Mutator transposase-like

proteins and an AT-hook protein.

The main objective of this project was to analyse the Mutator transposase-like and the

HMGA-like partial cDNAs to verify that these proteins do contribute to the regulation

of the FSltp6 promoter. The initial aim was to isolate full-length cDNA sequences for

each protein. A further aim was to perform functional analysis to determine the subcellular

localisation and expression profiles of each of the proteins. A full-length

sequence was identified for the Mutator transposase-like cDNA that encodes a

predicted 771 amino acid peptide sequence. Preliminary functional analysis was also

performed on both of the partial cDNA sequences and each showed expression in all

of the cotton tissues tested. Expression of both mRNAs were higher in the ovule and

6 DPA fibre compared to 12 DPA fibre, suggesting a potential role for these genes in

early fibre development.

Results from this project contribute to the field of cotton fibre development. More

specifically, this work contributes to the understanding of cotton promoters and their

roles in regulating fibre-specific expression. The full-length cDNA isolated in this

project could encode a transcription factor required for fibre-specific expression, but

further functional analysis must still to be performed for confirmation. Information

about cotton fibre-specific promoters and the transcription factors that regulate them,

such as the ones investigated in this study, could be used in the development of

transgenic cotton with improved fibre quality and yield.