A phenomics approach detected differential epigenetic growth regulation between inbreds and their hybrid in <Emphasis Type="Italic">Oryza sativa</Emphasis>

Epigenetic changes in chromatin can be induced upon hybridization, but their contribution to phenotypic changes in F1 hybrids is not known. In this study, we examined the effect of genome-wide alteration of epigenetic chromatin status on the growth of inbreds and their F1 hybrid by large-scale fine-time-lapse growth monitoring of rice (Oryza sativa L.) under a controlled environment. This allowed us to dissect seedling growth of inbreds and their hybrid into separate growth parameters, and to analyze the effect of disturbance of inert chromatin states on these parameters. We found that superior growth parameters are generally more sensitive to global inhibition of the activities of histone deacetylases (HDACs), but this higher sensitivity is not directly correlated to heterosis in F1. Unexpectedly, however, the rate of the initial exponential growth of shoots is sensitive to HDAC inhibition only in inbreds, but not in F1, irrespective of phenotypic superiority. Our phenomics approach has detected an inbred-specific dependence of basic growth on the inert state of chromatin that is lost in F1 hybrids.