Undergraduate Researcher University of California, San Diego San Diego, California
Body of Abstract: Root development is an adaptative process that plants modulate to survive in a variety of different changing environments and conditions. Anchor roots and root hairs are two important root structures produced from the integration of many developmental and environmental signals. The emergence of secondary root structures has been widely regarded as being integral for nutrient and water acquisition, as well as for plants to withstand natural adversities such as drought, nutrient deficiency, and soil disruption. However, the molecular mechanisms underpinning the development of these structures remain unclear. Here, I report a role for citrate in the pathways controlling the formation of these two important root structures in the model organism Arabidopsis thaliana that differ from its conventional role in ATP generation. Using buffered exogenous treatments in conjunction with transgenic lines, it was found that increasing citrate content induces anchor root formation and suppresses root hair growth. Genetic reporter lines for major phytohormones such as auxin, cytokinin and abscisic acid revealed changes in hormonal levels and indicates a crosstalk of signaling pathways with citrate in modulating secondary root structure development. Furthermore, analysis into reactive oxygen species (ROS) revealed that citrate causes significant changes in ROS homeostasis in developing roots as part of alterations at the transcriptional and posttranslational levels. We propose that endogenous citrate levels are one of the mechanisms that coordinate anchor root formation and root hair elongation through a combination of hormonal, redox and transcriptional processes. Understanding these uncharacterized mechanisms that enable plant survival is not only important for improving agricultural practices today but might even prove vital in a near future threatened by climate change.