Multiple Pathways in the Control of the Shade Avoidance Response

Plants have evolved two opposing strategies in response to competition for light: shade tolerance and shade avoidance. To detect the presence of neighboring vegetation, shade-avoiding plants have evolved the ability to perceive and integrate multiple signals. Among them, changes in light quality and quantity are central to elicit and regulate the shade avoidance response. Here, we describe recent advances in the understanding of photoperception and downstream signaling mechanisms underlying the shade avoidance response, focusing on Arabidopsis because most of our knowledge derives from studies conducted in this model plant. Shade avoidance is an adaptive response, resulting in phenotypes with high relative fitness in natural dense communities. However, it contributes to reduction in crop plant productivity, and the design of new strategies aimed at attenuating shade avoidance in a stage- and/or organ- specific manner in high-density crop plantings is a major challenge for the future. For this reason, in this review, we also report on recent advances in the molecular description of the shade avoidance response in crops, such as maize and tomato, and discuss similarity and differences with Arabidopsis.