Role of Phytochrome-Interacting Factors in Shade Avoidance Syndrome

Plants use changes in physical parameters of light, such as wavelength, intensity, direction, and duration as a source of information for various physiological adaptations. Shade decreases both the quality and quantity of light reaching photosynthetic organs of plants. Plants have evolved a series of responses collectively called shade avoidance syndrome (SAS) to consolidate light capture necessary for photosynthesis in canopy environments. SAS includes hypocotyl, stem and petiole elongation, hyponastic leaf movement, reduced leaf development and branching, and reduced root development. A subfamily of the basic helix-loop-helix (bHLH) transcription factor superfamily, phytochrome-interacting factors (PIFs), regulate shade avoidance syndrome by inducing expression of genes responsible for auxin production and transport, auxin sensitivity, and cell wall remodelling.