A NEW ARABINOGALACTAN PROTEIN-LIKE GENE EXPRESSED IN THE POLLEN OF ALFALFA

Differential screening of an alfalfa microspore/pollen cDNA library le d to the isolation of a cDNA clone (PO2) which contains an open readin g frame coding for a polypeptide with features characteristic of arabi nogalactan proteins. This deduced polypeptide is composed of 259 amino acids and has three distinct domains: an N-terminal signal peptide, a less hydrophobic central domain with several amino acid repeats, and a C-terminal hydrophobic domain. The predicted mature protein is rich in Ala, Ser and Pro, has a molecular mass of ca. 24 kD, a pi of 4.37 a nd no N-glycosylation sites. PO2 represents a low-copy-number gene in the alfalfa genome and is transcribed during the late stage of pollen development. The corresponding genomic sequence of PO2 has no introns and the promoter region contains no sequence in common with other euka ryotic promoters including plant pollen-expressed promoters. (C) 1997 Elsevier Science Ireland Ltd.