Aspartate aminotransferase isozymes in the genus Capsella (Brassicaceae): subcellular location, gene duplication, and polymorphism.

The subcellular location of aspartate aminotransferase isozymes (EC 2.6.1.1) in the genus Capsella (Brassicaceae) was studied. The diploid species C. grandiflora and C. rubella have three AAT isozymes, including one located in the plastids. Each locus is duplicated in the tetraploid Capsella bursa-pastoris. Variation at the plastid-coding locus exceeded that at the other loci. C. bursa-pastoris had some unique alleles not detected in the diploid species. Segregation in open-pollinated families revealed that Capsella grandiflora was outcrossing, whereas C. rubella was highly inbred, with most populations homozygous or uniform at all three loci. Inheritance in the tetraploid colonizer C. bursa-pastoris is disomic. This species was also predominantly selfing with outcrossing rates between 2% and 10%.