THE PROFILIN MULTIGENE FAMILY OF MAIZE - DIFFERENTIAL EXPRESSION OF 3ISOFORMS

Profilin is a small (12-15 kDa) actin- and phospholipid-binding protei n previously known only from studies on animals and lower eukaryotes b ut recently identified as a birch pollen allergen. Here we have identi fied and characterized three members of the profilin multigene family from the plant Zea mays. Two cDNAs isolated from a maize pollen librar y (ZmPRO 1 and ZmPRO 3) each have a single, large open reading frame e ncoding a putative polypeptide 131 amino acids long with a predicted m olecular weight of approximately 14 kDa. A third maize pollen cDNA (Zm PRO 2) has two in-frame translation initiation codons. Use of the firs t ATG would result in a polypeptide 137 amino acids long with a molecu lar weight of 14.8 kDa. The three maize profilins are highly homologou s to each other (>90% nucleotide and amino acid sequence identity) as well as other plant profilins but show far less similarity (30-40% ami no acid sequence identity) to animal and lower eukaryote profilins. Mu ltiple sequence alignments indicate that only nine residues are shared by all eukaryotic profilins examined. However, limited comparisons re veal domains in the NH2 and COOH termini that have a high degree of si milarity suggesting functional conservation. The maize gene family siz e is estimated to contain three to six members based on Southern blot experiments with gene-specific and coding region probes. Northern blot analysis demonstrates that the three maize profilin cDNAs characteriz ed here are utilized in a tissue-specific manner and are anther or pol len specific.