Evidence for alternative splicing of MADS-box transcripts in developing cotton fibre cells

The MADS-box family of genes encodes transcription factors that have widely ranging roles in diverse aspects of plant development. In this study, four cotton MADS-box cDNA clones of the type II (MIKC) class were isolated, with phylogenetic analysis indicating that the cotton sequences are of the AGAMOUS subclass. The corresponding transcripts were detected in developing cotton fibre cells as well as in whole ovule and flower tissue, with differential expression in stems, leaves and roots. Reverse transcription PCR showed extensive alternative splicing in one of the reactions, and 11 mRNAs of different intron/exon composition and length were characterised. Sequence differences between the transcripts indicated that they could not be derived from the same pre-mRNA and that the sequenced transcript pool was derived from two distinct MADS-box genes. Several of the alternatively spliced transcripts potentially encoded proteins with altered K-domains and/or C-terminal regions and the variant proteins may have altered cellular roles. This work is the first that describes MADS-box gene expression in elongating cotton fibres and adds to a growing body of evidence for the prevalence of alternative splicing in the expression of MADS-box and other genes.