The Arabidopsis Evidence for an Ancient Split between Profilin Gene Family ' Constitutive and Pollen - Specific Profilin C e n e s

Profilin i s a ubiquitous eukaryotic protein that regulates the actin cytoskeleton and recently has been identified as a potent allergen in pollen. We examined the profilin gene family i n the model plant, Arabidopsis thaliana, and found that it contained approximately 8 to 10 members. Four distinct profilin sequences, three cDNAs, PRF1, PRFZ, and PRF3, and two genomic clones, PRFl and P R M , were isolated and characterized. These genes encoded four distinct profilin isoforms of 131 to 134 amino acids. Northern and reversetranscriptase polymerase chain reaction analyses demonstrated that Arabidopsis PRFl was expressed in all major plant organs, whereas PRF4 was specifically expressed in mature pollen. Cene trees constructed from amino acid sequence data revealed the presence of two ancient, distinct profilin gene classes i n plants. PRF4 was in a