Security of our future food supply will depend on our improved understanding of how plants regulate photosynthesis in response to a changing environment. Carotenoids are important for photosynthetic efficiency because they expand the range of wavelengths for photosynthesis and protect the photosystems against photo-oxidative damage. As environmental light and temperature cues are major regulators of carotenoids, increased knowledge of these signaling pathways will assist future crop improvement programs. This project aims to combine modeling with experimentation to determine the molecular mechanisms through which light and temperature modulate carotenogenesis, providing novel avenues for efforts to improve photosynthesis in the face of environmental change. A major driving force for carotenoid production is the transcriptional control of Phytoene synthase (PSY). The phytochrome photoreceptors promote PSY expression, while the PHYTOCHROME INTERACTING FACTORS (PIFs) act as transcriptional repressors. This antagonistic module provides a simple but robust system to modulate carotenoid biosynthesis. The Giberellin regulated DELLA proteins also participate in the light control of carotenogenesis by impairing PIF1 capacity to bind to the PSY promoter. However, in the light, not only de-repressing effects, but active induction of PSY takes place, hinting at the existence of positive regulators of the pathway. Preliminary evidence points at LONG HYPOCOTYL 5 (HY5) for this role. Many phytochrome dependent responses are strongly influenced by temperature, suggesting a convergence of signaling at the molecular level. Because PIFs, DELLAs and HY5 are temperature responsive, they could be integration nodes for environmental control of carotenogenesis. We aim to characterize they key molecular events, the dynamics and emerging properties of the signaling for carotenoid production as a basis for future development of crops resilient to climate alterations.
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