From genotype to phenotype: systems biology meets natural variation

Abstract

The promise that came with genome sequencing was that we would soon know what genes do, particularly genes involved in human diseases and those of importance to agriculture. We now have the full genomic sequence of human, chimpanzee, mouse, chicken, dog, worm, fly, rice, and cress, as well as those for a wide variety of other species, and yet we still have a lot of trouble figuring out what genes do. Mapping genes to their function is called the "genotype-to-phenotype problem," where phenotype is whatever is changed in the organism when a gene's function is altered.

Fig. 1

Ways in which a hypothetical network could control flower form and color among Mimulus species. The widespread species M. guttatus (A) has large, yellow flowers. In contrast, the flowers of M. laciniatus (B) are typically 75% smaller than those of M. guttatus. Other species show elevated expression of red anthocyanin pigments (C), as in this hybrid between subspecies of M. luteus. Changes at various points in the network (represented by differing widths of the connections [arrows] between network nodes [circles]) could be responsible for this natural variation. [Photos by J. Modliszewski]

Fig. 2

Systems biology approaches can be applied to natural variation in wild relatives of Arabidopsis, such as this Boechera population on the continental divide in Montana (USA).