Six actin gene subfamilies map to five chromosomes of Petunia hybrida

The Mitchell variety of Petunia hybrida possesses a superfamily of actin genes which contains between 100 and 200 members that can be divided into at least six highly divergent subfamilies. The segregation of restriction fragment length polymorphisms among 96 plants from two backcrosses between the Violet 23 and Red 51 Petunia varieties and the Violet 23 x Red 51 hybrid was examined using gene-specific probes from six Petunia actin gene subfamilies. These data were compared with the genotypes of each plant at 11 marker loci which are distributed among the seven chromosomes of Petunia and which determine flower, pollen, and isozyme phenotypes. From these analyses, members of these six actin gene subfamilies were mapped to five locations on five Petunia chromosomes: the PAc9, PAc1, PAc4, and PAc2 subfamilies are on chromosomes I, II, III, and VII respectively; the PAc3 and PAc7 subfamilies are tightly linked on chromosome IV. All members of the PAc4 subfamily cosegregated as a cluster of genes. These data are discussed regarding gene amplification in plants.