Presenter: Ullas Pedmale, Assistant Professor at Cold Spring Harbor Laboratory
Title: How does shaded shoots control root growth?
Abstract: Roots and shoots live in different environments, yet the root knows when the shoot faces adverse environmental conditions. Shade avoidance response (SAR) triggered by the sub-optimal light environment from the nearby vegetation leads to rapid growth of the stem and petioles to maximize light capture but also leads to the poor growth of the roots. Roots not only serve as a mechanical anchor but plays a vital role in the well-being of the entire plant. As one can imagine, there is a negative cycle occurring during shading; shoot perceived shade leads to reduced root growth which in turn is unable to support the shoot leading to unproductive plants. Surprisingly not much is known about the mechanisms that affect root growth when the shoot detects changes in light conditions. Given the importance of the roots of the overall plant growth and productivity, we aim to understand the mechanisms by which root growth is affected by changing light conditions, especially in vegetative shading. Recent results from our study using a combination of genomics, genetics and biochemical approaches suggest that roots activate stress responses in the shade to slow down its growth by diverting resources to the shoot. These stress responses were activated by MAPK cascade and mediated by root-specific WRKY transcription factors. Surprisingly, we found that roots contained a large amount of free auxin but the auxin signaling was inactivated. These results provide a framework to explore the nature of signal from the shoot to modify root growth in changing light conditions.
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