Plants must have a highly branched root system for efficient moisture and nutrient acquisition. As a result of global climate change, drought is becoming more prevalent world-wide, driving the need for insight into root architecture that maximizes water uptake that may lead to development of drought tolerant crops. This project explores how root architecture is controlled by flavonoids, which are chemicals made by plants that function as antioxidants. Flavonoid antioxidants reduce the levels of reactive oxygen species (ROS), which act as signaling molecules to help plants adapt to stressful growth conditions, but can become toxic at high levels. ROS signals play important roles in the response of plants to changes in light, temperature, and drought. This project examines how ROS-dependent signaling pathways are induced and how flavonoids limit these signals to prevent oxidative damage. The planned experiments will use plants with mutations that alter flavonoid synthesis to demonstrate when and where flavonoids alter ROS levels in roots and how the accumulation of flavonoids alters root architecture. This project will also explore the mechanisms by which ROS modulates activity of proteins and expression of genes. This project will also support the development of a case study exercise targeted to high school students, which teaches plant genetics and how plants respond to drought and the potential of conventional breeding and genetic engineering of plants to lead to drought tolerant crop varieties. The team will bring college students to high school classrooms to lead students through this curriculum to better understand these concepts and how they apply to agriculture.
This project will examine the role of reactive oxygen species (ROS) as signaling molecules that control root development and examine how flavonoids scavenge ROS to modulate development. This project applies genetic, molecular biological, and biochemical approaches to examine and manipulate the flavonoid biosynthetic pathway in the model plant species of Arabidopsis thaliana to ask whether flavonoid effects on root architecture are the result of their antioxidant action. We have in hand mutants with defects at most steps in flavonoid biosynthesis, which we will use to determine which flavonoids control root architecture. We will localize and quantify ROS using confocal microscopy with a probes that detect specific reactive oxygen species to determine whether ROS accumulation and distribution are modulated by the different flavonoid accumulation profiles found in these mutants. We will use genetic and chemical approaches to manipulate the levels of ROS and ROS scavengers to demonstrate that flavonoid/ROS interplay is directly linked to root development. Finally, we will identify the mechanisms by which flavonoid-modulated ROS controls root development by exploring changes in transcriptional networks and using an unbiased proteomic approach to identify proteins that are reversibly modified by ROS in a flavonol-dependent mechanism. The function of ROS regulated gene products or ROS oxidized proteins will then be tested using a mutant approach.
