Organization and evolution of higher plant nuclear genomes

The knowledge gained from studies on eukaryotic genome organization is important for understanding how genomes function and evolve, and it provides the basis for designing strategies for manipulating genomes. Hence, numerous studies on this subject have been conducted over the years, utilizing a variety of methods. In the recent decade, several techniques have been developed that allow the study of eukaryotic genome organization at different levels. Molecular techniques including molecular cloning, DNA sequencing, restriction fragment length polymorphism mapping, in situ hybridization, and pulsed field gel electrophoresis together provide a means of obtaining a comprehensive and detailed view of eukaryotic genomes. This paper summarizes recent findings on the organization and evolution of the nuclear genomes of higher plants, with emphasis on representative species with varying genome sizes, including Arabidopsis thaliana, tomato, maize, and wheat. Common, as well as unique, features in the organization of repeated DNA sequences and low copy sequences in these genomes are described and their evolutionary significance discussed.Key words: genome organization, evolution, higher plants, repeated DNA sequences, low copy number sequences.