Arabidopsis profilins are functionally similar to yeast profilins: identification of a vascular bundle-specific profilin and a pollen-specific profilin.

Four members of the Arabidopsis profilin (pfn) multigene family have been cloned, sequenced and analyzed. By RNA gel blot analysis it has been shown that these four genes fall into two groups: one group (pfn1 and pfn2) is expressed in all organs of the plant and the other group (pfn3 and pfn4) in floral tissues only. Based on amino acid sequence alignment Arabidopsis profilins can be divided into the same two groups: PFN1 and PFN2 are 89% identical and PFN3 and PFN4 are 91% identical. Between these two groups they are 71-75% identical. The Arabidopsis profilins bind poly-L-proline and can complement both the Saccharomyces cerevisiae profilin deletion mutant and the Schizosaccharomyces pombe cdc3-124/profilin mutation, showing that the plant profilins are functionally similar to yeast profilins despite the low amino acid sequence homology. Analysis of pfn promoter-GUS fusion genes in transgenic Arabidopsis shows that pfn2 is specifically expressed in the vascular bundles of roots, hypocotyls, cotyledons, leaves, sepals, petals, stamen filaments and stalks of developing seeds, whereas expression of pfn4 is restricted to mature and germinating pollen grains.