ABSTRACT
Paramutation is a case of non-Mendelian inheritance, long known, but still incompletely understood. It describes the change of gene expression at a paramutable allele by encounter with a paramutagenic allele, causing an alteration that remains even after segregation of both alleles. While discovery, genetic and mechanistic studies of paramutation were made with alleles that change plant pigmentation, paramutation-like phenomena are also known for other traits and in other organisms, and many cases probably went undetected. Paramutation between epialleles, genes with identical sequences but different expression states, argues for an epigenetic mechanism, providing profound evidence that triggered epigenetic changes can be maintained over generations. Here, we use a case of paramutation that affects a transgenic selection reporter gene in tetraploid Arabidopsis thaliana, to study the role of small RNAs, epiallele structure and copy number, and environmental influence on degree and timing of paramutation. Our data suggest that different types of small RNA associated with the epialleles, the presence of repeats, and the growth temperature of the epiallelic hybrids contribute to the strength of the allelic interaction. The data further make it plausible why paramutation in this system becomes evident only in the segregating F2 population of tetraploid hybrids. In summary, the results support a model for polyploidy-associated paramutation, with similarities as well as distinctions from other cases of paramutation.
Competing Interest Statement
The authors have declared no competing interest.
