Introduction to Harmon Lab Research

Below, find examples of our research projects.

Temperature and the circadian clock

Temperature is an overlooked player in studies of the circadian clock. While it is true that light has the strongest influence on setting the circadian clock, temperature is also crucial in regulating circadian rhythms. While plants are in constant conditions in terms of light (continuous light or continuous dark), 24-hour cycles of warm/cool are sufficient to set oscillations correctly: dawn corresponds to a rise in temperature and dusk to a decrease in temperature. In addition, circadian rhythms exhibit temperature compensation, which is the ability to maintain precise 24-hour rhythms despite external temperature fluctuations. The circadian clock is thus able to “learn” from temperature cycles whether it is day or night, while also making sure circadian rhythms never speed up or slow down if the environment gets hot or cold.

Heterosis and the circadian clock

Hybrids and allopolyploids often show hybrid vigor or heterosis: increased growth, biomass, and fertility compared to the inbred parents. 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.

The maize circadian clock

By researching circadian genes in major crop plant species, we will begin to understand how crop plants modify their internal processes in accordance with environmental cues. Zea mays (maize) is among the most important crops grown worldwide, and an established experimental model for plant biology. Genetically, maize is remarkable as it has undergone whole genome duplication and retained multiple copies of each clock gene. Moreover, the natural diversity of maize varieties provides an extraordinarily varied set of circadian clocks to study. Investigating the signaling networks within the maize circadian clock is an important step toward practical application of insights from clock research to agriculturally significant crops.