Gene expression non-additivity in immature ears of a heterotic F1 maize hybrid

Non-additive gene regulation has been recently suggested as an important factor promoting phenotypic variation and plasticity. In order to obtain a description of gene expression status at an early stage of ear development in a maize (Zea mays L.) F1 hybrid as relative to its parental inbreds, we compared gene expression profiles in immature ears of elite inbred lines B73 and H99 to one of their F1 hybrids (B73 × H99) using cDNA microarray technology. Results show several genes expressed at a significantly different level between both inbred lines and their hybrid. In addition, gene expression non-additivity in the hybrid was detected on a broad scale, consisting of both dominance and over-dominance components, indicating that complex non-additive interactions at the molecular level exist in the developing ear of the studied maize hybrid. Non-additively regulated genes belong to a wide range of molecular functions, indicating that several regulatory and metabolic patterns are possibly affected during ear development in the investigated hybrid. We discuss the possibility that observed gene expression non-additivity in immature ear might be an early molecular manifestation of hybrid vigor, the most exploited factor for maize agronomic improvement.