How does PAP, a stress-induced metabolite, regulate gene expression?
Plants are commonly exposed to environmental fluctuations (such as extremes in temperature or insufficient water) which are sufficient to limit crop yield in both field-grown and glasshouse-grown contexts. Damage induced by such stresses is typically first observed within the chloroplast and mitochondria, where perturbations in metabolism rapidly induce oxidative stress. These perturbations are communicated from organelles to the nucleus via multiple retrograde signaling pathways that alter nuclear gene expression, allowing plants to adjust their metabolism and development to tolerate environmental stress. However, the extent to which retrograde signals can regulate plant homeostasis, and by what mechanism(s), remain enigmatic.
Many abiotic and biotic are predominantly associated with specific times of day, driving the evolution of biological timing mechanisms that enable anticipation of biotic and abiotic stresses associated with either day or night. These biological timers (commonly referred to as the circadian system) have subsequently been co-opted to modulate many physiological processes including growth, photosynthesis, and flowering time. In addition to providing an endogenous timing reference, seasonal changes in daylength require that the circadian system is synchronized with environmental factors such as dusk and dawn. This induces a complex interplay between environmental signals, endogenous biological timers, and metabolic changes induced by sub-optimal environmental conditions. If we are to fully exploit the potential yield of crops it is vital that we understand how plants interact with their environment during daily environmental fluctuations.
As part of our efforts to understand these interactions we have demonstrated that a signaling metabolite induced by drought is sufficient to delay the circadian system (Litthauer et al., 2018). Such data demonstrates how changes in metabolism arising from the application of stress can induce changes in gene expression, ultimately altering plant behavior.
The successful applicant will utilize genetic resources available in the model plant Arabidopsis thaliana to decipher the mechanism that links light and drought stress with the circadian system using a combination of biochemical, genetic, and bioimaging approaches.
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