Two related flower-expressed gene copies
belonging to the SF21 (sunflower-21) gene family have
been isolated from Senecio squalidus These gene copies are differentially expressed
in pollen and pistil tissues; ORSF21B (Oxford Ragwort
SF21B) is expressed exclusively in mature pollen, whereas
ORSF21A (Oxford Ragwort SF21A) is expressed in the
transmitting tissue of the style, where it is developmentally
regulated. Despite differences in expression, the coding
regions of ORSF21A and ORSF21B are highly similar.
Amino acid sequence alignments of SF21 genes from a
number of angiosperm species indicate that this gene
family is conserved in flowering plants and may play an
important role in reproductive processes in a wide range of
taxa. Phylogenetic analysis of SF21 nucleotide sequence
alignments supports this theory, and indicates a complicated
history of evolution of this gene family in angiosperms. The putative roles of SF21 genes in reproduction and pollen–pistil interactions are discussed.