Cloning and characterization of PO22, a pollen-expressed gene in alfalfa.

Genomic and cDNA clones have been isolated for a new gene (PO22) expressed in mature pollen of alfalfa. PO22 represents a single- or low-copy gene containing 4 introns, 2 transcriptional start sites, and coding for a predicted protein of 340 amino acids with no signal peptide and a coiled coil structure of 39 amino acids near the carboxyl end. The amino acid sequence of PO22 is 38% identical to that of an early nodule-specific gene (ENOD8), also from alfalfa.