Heritable Alteration of the Maize Methylome following Tissue Culture

Somaclonal variation can occur in plants derived from tissue culture.  There is evidence that somaclonal variation can be the result of novel transposon insertions or altered epigenetic state.  We sought to determine how the maize methylome is influenced by tissue culture.  Several independent cultures were derived from the inbred line A188 and used to regenerate plants.  Whole-genome profiling of DNA methylation revealed a number of differentially methylated regions in plants derived from tissue culture relative to siblings that had not been subjected to culture.  Hypomethylation events were more common than hypermethylation events and are often found in 5’ regions of genes.  Many of the regions display hypomethylation of both alleles in multiple independent events.  The regenerated plants were self-pollinated to produce R1 plants in order to assess whether altered DNA methylation levels were stably transmitted to off-spring.  Many of the hypomethylation events were stably inherited following sexual reproduction.