New Perspectives on Shade Avoidance

As sessile organisms, plants are unable to move to more favorable environments and must instead adjust to the conditions in which they are growing. In response to changes in light quantity and quality, plants can initiate a shade avoidance response that includes elongated hypocotyls, increased leaf angle, elongated internodes and petioles, and early flowering. While potentially advantageous for the individual plant, this response can divert resources from agronomically relevant tissues, leading to undesirable outcomes in crowded agricultural settings.  Many advances in our understanding of this process have been made from studies on Arabidopsis hypocotyls, which serve as an excellent, yet incomplete model.  Here we demonstrate that complementary approaches using natural variants and additional developmental stages can lead to new discoveries of how the shade avoidance pathway works.  Analysis of hypocotyl shade responses across a panel of natural variants confirmed previously identified shade avoidance genes as well highlighted novel genes, revealing the strong potential of natural variation as a means of identifying important genes.  To broaden our model to tissues beyond the hypocotyl, we combined RNAseq on leaf tissue with mutant phenotypic analysis to show that there are important shade avoidance genes specific to later developmental stages.  These studies highlight the utility of new approaches in refining our working model of shade avoidance in plants.