In this study, authors tried to establish a causal relationship between changes in methylation patterns and acquired traits. To this end, they exposed rice seeds to azadC, and a line was selected from the surviving seedlings ('Line-2'), which was somehow phenotypically different from the wild type. From here, and although there was no conclusive evidence for a transgenerational effect so far, authors wrote:
[...] a pulse treatment of germinated seeds with azadC had induced phenotypic changes evident at maturity, and that such changes were stably inherited by the progeny.To demonstrate that their observation had an epigenetic origin, they evaluated the methylation status of some loci using digestion with methylation- sensitive restrictases followed by blotting, but they found no significative differences. Perhaps a global methylation assay in this step could have been more informative. They later identified ~20 MSAP unique fragments in Line-2, one of them -termed 'HMF2'- predictably showing similarity to retrotransposon sequences; bisulfite analysis of HMF2 indicated that this fragment was hypomethylated in Line-2. Another fragment, HMF5, related to a pathogen- resistance gene, was also hypomethylated in the studied clone. Authors mentioned that this acquired change was directed instead of being at random, and that these sequences were methylated in wild type plants to prevent recombination, because they also contained a downstream retrotransposon sequence. Although these evidences were insufficient to prove the stable inheritance of methylation status in these plants, they concluded that:
[...] It was thus suggested that methylation/demethylation does occur under natural conditions, and that heritable epigenetic mutations play a significant role in evolution. The present finding substantiates this idea, showing that gene expression is flexibly tuned by methylation, allowing plants to gain or lose particular traits which are heritable as far as methylation patterns of corresponding genes are maintained. This is in support of the concept of Lamarckian inheritance, suggesting that acquired traits are heritable.Clearly, a more detailed study is needed. And perhaps this next time the future authors will give a more informative title to their paper, instead of using this very generic and misleading one.
Akimoto K. et al. 2007. Ann Bot 100(2):205-217
epigenetics
