Maize was where it all began in the 1940’s when Barbara McClintock discovered transposable elements (TE’s) in the popular cereal grain, and Maize is again at the forefront of transposons studies. The Maize kernel has been ideal for studying the interaction between TE’s and host genomes because kernels on a maize ear show unstable phenotypes due to interplay between a TE and a gene that encodes an enzyme in the pigment biosynthetic pathway.
While debate continues whether TE’s are agents of evolution or parasitic passengers, SanMiguel et al. has provided evidence, for the first time, that TE’s can rapidly restructure a genome. Over the past 3 million years the Maize genome has doubled in size due to a burst in retrotransposon activity. The study determined the insertion dates for 17 of the 23 retrotransposon found near the maize adh1 gene and discovered that retrotransposon insertions have increased the genome size from approximately 1200 Mb to 2400 Mb!
Was this flurry of activity a response to stress? This would be consistent with the genome restructuring role envisioned by McClintock all those years ago. Continuing down this line of research has the potential to provide mechanisms that will explain how evolution works and a molecular level.
Submitted by: s4123804
