BRC-BIO: Investigation of the role of the plant hormone, abscisic acid, in stomatal formation using a novel drought-tolerant mutant

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In the wake of changing climate, drought has become a major environmental threat that impairs crop productivity worldwide. Stomata, micro-pores on the leaf surfaces of terrestrial plants, can open and close to allow carbon dioxide into the leaf and water vapor to escape. Water evaporation via these structures is estimated to explain over 90% of water loss from plants. Thus, a detailed understanding of how plants respond to drought to mediate water loss can inform approaches to reduce crop loss due to drought. Stomatal conductance is an overall measure of the exchange of carbon dioxide or water vapor via the stomata; it responds to both the number of stomata and how open they are, thus providing an indicator of drought stress. The plant hormone abscisic acid (ABA) is a stress-related hormone that directly responds to drought stress by regulating stomatal conductance. While the role of ABA in signaling stomata to close has been extensively explored, the mechanisms by which ABA signals the plant to increase or decrease the number of stomata remains elusive. The research aims of this study are designed to provide insight into plant drought tolerance by exploring the ABA function in stomatal formation. Much of the research will be conducted by four undergraduate students from underserved communities. These students will be mentored by the PI and a graduate student and will serve as peer mentors to each other. Production of the genetically engineered plants generated in this study, and the phenotypic analyses thereof, will serve as the basis for development of a new undergraduate laboratory course. Students taking this course will receive extensive hands-on training in a complete set of widely used techniques, which will promote their science identity and better prepare them for professional STEM careers.The PI’s group has identified a drought-tolerant mutant, which produces stomata more slowly under drought conditions than when well-watered. Analysis of the mutant under drought stress has revealed that ABA signaling is enhanced and a transcription factor that promotes stomatal formation is preferentially inhibited. The PI hypothesizes that ABA mediates drought-triggered stomatal inhibition by targeting stomatal-associated transcription factors in the mutant. This hypothesis will be tested by two aims to: 1) examine the role of ABA in drought-triggered stomatal inhibition in the mutant, and (2) identify the transcription factor targeted by the ABA signal in the stomatal developmental pathway in the mutant. The results have the potential to provide new insights into how drought controls stomatal numbers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.