Published Research on Single Gene Expression Assays
Expression of 40 homoeologous gene pairs was assayed by cDNA-SSCP in natural (1-2 million year old) and synthetic tetraploid cotton (Gossypium) to determine if homoeologous gene pairs are expressed at equal levels following polyploid formation. Silencing or unequal expression of one homoeolog was documented for 10 of 40 genes examined in ovules of G. hirsutum. Assays of homoeolog expression in 10 organs revealed variable expression levels and silencing, depending on the gene and organ examined. Remarkably, silencing and biased expression of some gene pairs are reciprocal and developmentally regulated, with one homoeolog showing silencing in some organs and the other being silenced in other organs, suggesting rapid subfunctionalization. Duplicate gene expression was examined in additional natural polyploids to characterize the pace at which expression alteration evolves. Analysis of a synthetic tetraploid revealed homoeolog expression and silencing patterns that so metimes mirrored those of the natural tetraploid. Both long-term and immediate responses to polyploidization were implicated, as were epigenetic causal factors. Data suggest that some silencing events may be epigenetically induced immediately upon polyploidization and maintained over millions of years. See Adams, Cronn, Percifield and Wendel (2003) for more information.