Changing host specificities: By mutational changes or epigenetic reprogramming?

Abstract

Weedy Orobanchaceae often change host specificity at a rapid rate. These changes and the equally fast reversions to the previous host specificity are hard to explain by Mendelian mutations. The altered phenotype could be due to epigenetic reprogramming of gene expression. Conventional DNA analysis technologies can be used to ascertain whether epigenetic changes are involved. Epigenetic changes are caused by higher level alterations to the DNA structure such as histone modifications or cytosine methylation, but only the latter is maintained through meiosis in plants. Alternative splicing of mRNA could theoretically also be responsible for some cases. Methods for ascertaining changes in methylation patterns that could be adapted to determine whether changes are epigenetic are briefly described. Crosses can also be used to ascertain whether the adaptation to new hosts is genetic, although results may be ambiguous and could be confounded by reversion if the changed host specificity was epigenetic.