MOLECULAR-CLONING OF GENES EXPRESSED IN POLLEN OF SORGHUM-BICOLOR

We have screened a cDNA library of sorghum mature pollen with maize an d Tradescantia paludosa pollen-specific clones with the aim of isolati ng the corresponding sequences in Sorghum bicolor, one of the most imp ortant crops in the semi-arid tropics. Six cDNA clones were isolated a nd their pollen-specificity was determined by Northern blot analysis. Two clones, MSb8, homologous to the maize clone Zm13, and MSb2.1, homo logous to the Tradescantia clone Tpc44, have been characterized. MSb8 contains a cDNA of 745 bp that hybridizes to a pollen-specific mRNA of approximately 900 nucleotides. The analysis of its nucleotide sequenc e shows an open reading frame corresponding to a putative 19.2 kDa pep tide of 173 amino-acid residues, with more than 90% of similarity with Zm13 peptide. MSb2.1 seems to be member of a small multigene family a nd shows homology to sequences expressed in mature pollen of maize and pearl millet and present in the rice genome too.