Comparative genomics provides a powerful approach to identifying conserved non-coding sequences that regulate gene transcription. In the April 30 Proceedings of the National Academy of Sciences Kaplinsky et al. report the use of cross-species genomic DNA comparison to isolate conserved non-coding sequences in grass genomes (Proc Natl Acad Sci USA 2002, 99:6147-6151). They compared the genomic sequences of rice and maize, two domesticated species in the Poaceae family of grasses. Differences in regulatory sequences between grasses are thought to account for their morphological and physiological variation. Kaplinsky et al. examined genomic sequences around the liguleless1 (lg1) gene, which is required to specify the ligule. They identified several conserved non-coding sequences by comparing genomic sequences, relative positions and lengths; and the conserved Ig1 non-coding sequences are also conserved in other grass species, including Staria, Arundo and bamboo. Analysis of conserved non-coding sequences from other rice and maize genes suggests that such sequences are smaller and less frequent in plants than in mammalian genomes.
Proceedings of the National Academy of Sciences