Poster: Regulation of gene expression

Abs # 734: Characterization and promoter analysis of the cotton fiber gene CDKA encoding an A-type cyclin-dependent kinase

Presenter:	Gao, Weifan , wg1@ra.msstate.edu
Authors	Gao, Weifan  (A)   Ma, Din-Pow  (A)
Affiliations:	(A): Mississippi State University

Cyclin-dependent kinases (CDKs) play a key role in the regulation of cell division. The progress of cell cycle phases in eukaryotes is controlled by the activity of distinct CDKs, which is modulated by their phosphorylatiuon and binding to their cyclin partners and inhibitory proteins. Cotton (Gossypium hirsutum L.) fibers are epidermal cells differentiated from the outer integument of a developing seed. Fiber cells are unable to undergo cell division during fiber development. However, it was recently reported that fiber cells can undergo cell division when the 2-3 DPA (days postanthesis) ovules were removed from bolls and cultured under in vitro conditions. As a first step to understanding the mechanism of fiber cell division and differentiation, we have cloned and characterized a fiber CDK cDNA (CDKA) and its corresponding genomic sequence. The fiber CDKA encodes a protein containing 294 amino acids. The protein contains the conserved PSTAIRE motif of A-type CDKs in the cyclin-binding domain. Comparison of genomic and cDNA sequences indicates that the CDKA coding region is split by 7 introns. Genomic Southern analysis indicates that there are at least two copy numbers of the CDKA gene in the cotton genome. Northern blot and semi-quantitative analysis data reveal that the CDKA gene is strongly expressed in 5-10 DPA fibers. Promoter analysis shows that the 5’-flanking region of the CDKA gene can direct GUS expression in 5-10 DPA fibers. Bacterial two hybridization assays reveal that the CDKA can interact with a number of fiber proteins, including a cyclin D, a hydroxyproline rich protein, a camodulin binding protein, a phosphate induced protein, protein kinases, transcription factors, and hypothetical proteins.