Hybrids and allopolyploids often show hybrid vigor or heterosis: increased growth, biomass, and fertility compared to the inbred parents (shown below). A recent study in Arabidopsis hybrids and allotetraploids found that alterations in the expression waveform of key circadian clock genes appear to up-regulate metabolic outputs including chlorophyll biosynthesis and starch metabolism (Ni et al. 2009 Nature). These increased metabolic outputs are important in producing heterosis in hybrids. Together with the Chen lab, the Harmon lab is studying the effect of circadian clock genes on maize metabolism and vigor.
Studying the mechanisms of maize heterosis is important in the context of US agriculture: since hybrids display vigor in yield, most maize grown in the US is from hybrid seed, and maize is the most prevalent and profitable crop in the US. In the Harmon lab, we are measuring maize core circadian clock gene expression and metabolic output in inbreds and hybrids. We are also measuring these parameters in plants with increased, decreased, or shifted expression of core circadian clock genes by creating insertional mutants, overexpression and RNAi lines. The goal of this project is to draw causal links between the vigor we observe in hybrids, and changes in expression of core clock genes.
