Many major crops use hybrids between different lines to produce more robust and higher yielding plants in the field. This phenomenon is referred to as hybrid vigor or heterosis. The genetic and molecular basis of this phenomenon has been debated for over a century. This project will address the hypothesis that heterosis results from a generalized overall stimulation of gene expression in hybrids compared to their respective parents. The overall stimulation of gene expression results in larger and more cells in the hybrid than in the parents, thus producing progeny that have greater biomass. A genetic and molecular understanding of heterosis will provide the potential to improve crop production in predictable and expedited ways. If a unifying principle of heterosis can be established, it should become possible to edit plant genomes for better crop cultivation. The amount of arable land worldwide has been decreasing for several decades but the need for increased agricultural output is only increasing. The foundations established in this project will hopefully contribute to this need by providing for and advancing agricultural biotechnology through basic research. Several lines of evidence indicate that there is a transcriptome size increase in heterotic genotypes compared to their inbred parents. Generally, the expression of regulatory components is additive in hybrids and in a more stoichiometric register with each other than in their parental inbreds while the overall ex