Circadian Rhythm Regulates Growth of a Biotrophic Pathogen on Arabidopsis Thaliana

Most organisms have an internal biological clock, called the circadian rhythm. The clock is synchronized by the day–night cycle, allowing the organism to accommodate the daily cycles of light and dark attributable to the Earth’s rotation. Circadian clocks have three basic properties, they: have a period length of about 24 hours, can be reset by environmental factors such as light and temperature, and have at least one internal autonomous circadian oscillator. These oscillators contain positive and negative elements that form autoregulatory feedback loops, and in many cases these loops are used to generate 24-hour timing circuits.
Identification of clock-regulated genes leads to the determination of the common elements that regulate these genes. If these common elements can be identified, it enables the search for the same elements in potential virulence factors. This would give us information on whether the virulence factors are also regulated by the circadian rhythm. Since the link between plant immune system and the circadian clock has been identified, it is imperative that we identify the link between the pathogenicity factors and the circadian rhythm.
Arabidopsis thaliana and its natural biotrophic pathogen Hyaloperonospora arabidopsidis (Hpa) have been used as a model system for this study. Pathogen growth has been investigated under normal (light–dark cycle) and different light conditions (light–light and dark–dark cycles) to understand whether the circadian rhythm has an effect on pathogenicity. In addition, RNA-seq experiments were performed to elucidate differentially expressed genes in both plant and the pathogen.