Crop Biotech Update

Direction of Plant Genome Evolution

May 30, 2008

The apparent lack of correlation between the genome size of an organism and its complexity has long puzzled scientists. Simple organisms, like some fungi and bacteria, could have genomes that are many times larger than more complicated ones.

 It has become clear that transposable genetic element play a role in genome size growth especially in plants. Recent studies on maize and cotton revealed that their genome sizes have significantly increased over the past few million years due to proliferation of retrotransposons, mobile genetic elements that can amplify themselves in the genome. Evidences suggest that the direction of plant genome size change is biased toward increase, albeit there must be some limit on genome size growth. Plants employ several mechanisms such as homologous recombination to remove “junk” DNA. The question remains, nonetheless, if these mechanisms really contribute in downsizing the genome.

The review paper by Hawkins et al. is available at