SHADE AVOIDANCE

Environmental cues relay information to endogenous growth and developmental programs through complex signal transduction networks. Light is the most important of all environmental cues that influences development throughout plant’s life cycle. As many of the most promising food and biofuel feedstocks are grasses, there is growing interest in understanding the signaling mechanisms regulating light-mediated control of biomass, particularly in the context of high density plantings. Currently, our understanding of the molecular components of light signaling is limited in panicoid grasses and requires a model genetic system that is closely related to major food, fuel and bioenergy grasses. The goal of this research is to characterize light-mediated signal transduction pathways underlying agronomically important traits in the emerging model system for C4 grasses, Setaria viridis (S. viridis).

A physiological phenomenon that is of interest is shade avoidance response in grasses. Under the current scenario of rapid population increase, achieving efficient and productive agricultural land use calls for high planting densities to maximize yield/biomass per acre. A shade environment accompanies a light quality change that is perceived by a class of plant photoreceptors, phytochrome and induces a host of adaptive changes in plant architecture allowing them to compete with neighboring plants for limited resources. Since this developmental plasticity comes at the expense of yield, domestication of cereal grasses has been successful at attenuating shade avoidance response. However, major bioenergy grasses have not undergone such intense selection to achieve considerable attenuation of shade avoidance response under high-density plantings.

Effective engineering of grass architecture to maximize biomass and modify biomass properties in bioenergy grasses at increasing plant densities will require a broad understanding of molecular mechanisms underlying responses to vegetative shade. Since S. viridis is closely related to major food, feed and bioenergy grasses in the clade Panicoideae, it offers an excellent model system for forward and reverse genetics in characterizing downstream effectors of shade avoidance response. Development of reverse genetics tools in S. Viridis and comprehensive analysis of the phytochrome-mediated signaling cascades will be advantageous to functionally characterize candidate genes to manipulate grass architecture for increased productivity, biomass, feed, food and biofuel production, as well as modify biomass properties in closely related bioenergy grasses.

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