Global DNA methylation predicts epigenetic reprogramming and transgenerational plasticity in Poa annua L

Abstract

Poa annua L. (annual bluegrass) is a remarkably versatile grass species with biotypes ranging from perennial to annual. Despite its recent evolutionary origins, Poa annua can be found as an invasive weed on all seven continents of the globe including extremely inhospitable locations such as Mount Kilimanjaro and the Antarctic mainland. The molecular mechanisms underlying Poa annua versatility are unresolved but thought to relate to its neoallopolyploid origin and influence diverse molecular responses ranging from DNA methylation to chromosomal architecture. Fluorescence in situ hybridization (FISH) karyotyping of 5S rDNA loci added further evidence for Poa infirma Kunth. (weak bluegrass) and Poa supina Schrad. (supina bluegrass) as the progenitor species of Poa annua while results of 45S rDNA were less clear and possibly suggest that large-scale variation in chromosomal architecture might have occur between individual Poa annua genotypes. At the methylation level, abiotic stress was observed to induce global DNA methylation, and methylation in the progeny of stressed plants remained slightly elevated, suggesting partial heritability of the methylation landscape acquired through abiotic stress on the parents. Further, the progeny of mowed clones had 37% reduced shoot area when compared with the progeny of unmowed clones across eight genotypes, suggesting that the altered phenotype is non-Mendelian inherited. Poa annua plasticity and transgenerational inheritance is correlated with increased DNA methylation at the global level but causality needs experimental validation. These results suggest that Poa annua plastic phenotype is matched by genetic and epigenetic plasticity.