Heterosis, gene expression and structural variation

Heterosis, the superior performance of hybrids relative to their parents, is considered the major driver of yield increase in maize in the last decades, but its molecular basis is still not very well understood despite extensive research. One mechanism that may contribute to heterosis is the complementation of single-parent expression (SPE) genes in the hybrids. SPE genes refer to genes that are only expressed in one of the parents, caused either by differential regulation of gene expression (gene on/off) or structural variants (gene present/absent). In this study, we analyzed transcriptome data from multiple tissues of 80 maize hybrids derived from 33 parental lines to comprehensively characterize SPE genes in maize. One of our main findings is that SPE genes are highly specific to genotypes and tissues, and that larger genetic distances between parents are correlated with a larger number of SPEs in the hybrids.