CS-10-6 - Reactive oxygen species and flavonols modulate the root gravitropic response

Sunday, July 15
4:58 PM - 5:00 PM

During the gravitropic response, a root disturbed from its vertical orientation will grow asymmetrically so that it returns to the vertical orientation. Redistribution of auxin to the lower side of the root allows the top side of the root to grow faster than the lower side, ultimately facilitating a return to downward growth. Previous work showed that flavonols, which are antioxidants synthesized in plants, are required for normal gravity response kinetics. However, little is known about the role of reactive oxygen species (ROS), which are scavenged by flavonols in vivo, during root gravity response in Arabidopsis thaliana. To test the role of ROS, we evaluated the gravity response kinetics of mutants and roots treated with inhibitors of ROS synthesis and degradation. Members of the respiratory burst oxidase (rboh) mutant family, in which superoxide synthesis is inhibited, show delayed gravity response, as visualized by high resolution time course imaging. Seedlings treated with the 3-aminotriazole (3AT), which inhibits catalase, an enzyme that degrades hydrogen peroxide, show delayed gravity response. These results suggest that ROS homeostasis is required for gravity response to proceed normally. Treatment of wild type seedlings with the flavonol precursor naringenin results in an initial delay in gravity response, but ultimately inhibits homeostatic autostraightening, suggesting that increased flavonol-mediated ROS scavenging impairs both initiation and termination of asymmetric gravitropic growth. We have detected asymmetries in flavonol synthesis and ROS accumulation across gravistimulated roots and ongoing experiments are dissecting the timing of these asymmetries relative to auxin accumulation in gravistimulated roots using confocal microscopy and fluorescent sensors and reporters. Ultimately these experiments will provide insight into the relationship between auxin and ROS signals that modulate the root gravitropic response. (Supported by an ASPB SURF to ERS, NASA grant NNX15AG55G to CW, and NSF IOS-1558046 to GKM).



Chris Wolverton, PhD – Ohio Wesleyan University; Gloria Muday, PhD – Wake Forest University

Elizabeth Sarkel

Wake Forest University


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CS-10-6 - Reactive oxygen species and flavonols modulate the root gravitropic response

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