CHARACTERIZING ALLELIC PROTEINS FOR GENOME MAPPING IN MAIZE

Mapping cDNA probes in order to construct genetic linkage maps is beco ming a widespread strategy for genome analysis and gene isolation, par ticularly in cultivated plant species. Nevertheless, almost all cDNAs reveal two or more unlinked loci, making it difficult to identify the gene(s) actually expressed. In a highly polymorphic species, such as m aize, two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) of proteins may circumvent this limitation. With the analysis of various segregating populations, we previously showed that the apparent posit ion shifts of proteins on the 2-D gels are monogenic and codominant. I n this paper we compared allelic proteins on the basis of their high p erformance liquid chromatography (HPLC) profile and partial amino acid sequences. In a sample of 20 position shifts, the allelic proteins ap peared to be similar in all but one case, strongly suggesting that pol ymorphism of structural genes is involved. Thus 2-D PAGE could prove t o be a useful tool for genome mapping: when a cDNA probe detects sever al loci, a position shift of the encoded protein will allow the identi fication of the gene translated in the organ considered.