Transposable elements make up a substantial proportion of most plant genomes. Because
they are potentially highly mutagenic, transposons are controlled by a set of mechanisms
whose function is to recognize and epigenetically silence them. Under most circumstances
this process is highly efficient, and the vast majority of transposons are inactive.
Nevertheless, transposons are activated by a variety of conditions likely to be encountered
by natural populations, and even closely related species can have dramatic differences in …