Collaborative Research: Deciphering the molecular mechanisms of hormone-like function of terpenoids

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Plants emit an amazing diversity of volatile organic compounds (VOCs) that play numerous roles in plant growth and development. They are also targets of released compounds as a part of plant-plant communication, as well as plant-insect and plant-microbe interactions. Plants are constantly exposed to atmospheric VOCs and can differentiate and respond to specific cues, therefore VOC perception is an essential part of information exchange. Due to the plethora of biological processes dependent on VOCs, significant progress has been made towards understanding the biosynthesis of plant VOCs and their regulation, and, in recent years, the molecular mechanisms involved in VOC emission. However, to date little is known about how VOCs are perceived by plants and trigger cellular response(s). This project will characterize signaling pathway(s) involved in perception of volatiles and mode of action of volatile signals, particularly terpenoids, in plant growth and development. This research will also answer the long-standing question about the nature of unknown endogenous plant signaling molecule(s). The results will fill important gaps in our understanding of plant olfaction and elucidate the molecular mechanisms underlying volatile perception and responses in plants. The obtained information will be groundbreaking for our understanding of plant interactions in the ecosystem and uncover the differences between volatile perception in plants and that in animals and insects. Given the VOC multifunctionality and overall lack of understanding of volatile perception in plants, this research will identify new targets for metabolic engineering for simultaneous improvement of plant defense and fitness. The proposed research will provide multidisciplinary training to undergraduate and graduate students, and postdoctoral researchers. The educational program will also introduce STEM-based research to a local middle school with minority students. The goals are to improve student enthusiasm, interest, and perceptions about scientific careers.Perception is an essential part of plant-plant, plant-insect and plant-microbe interactions, but the molecular mechanisms remain unknown. The absence of reliable molecular markers of the perception state makes the investigation of plant communication difficult. The recent discovery in petunia flowers of inter-organ aerial transport of volatiles via natural fumigation and hormone-like function of terpenoids, provides an excellent platform for investigating the mode of VOC perception and dissecting signaling cascade(s) involved. Preliminary results in Petunia hybrida flowers led to hypothesis that a karrikin-like signaling pathway is involved in perception of volatile signals via a karrikin-insensitive receptor, PhKAI2ia, and mediates terpene-dependent stigma development. This research will employ an integrative strategy comprised of genetics, molecular biology, biochemistry, metabolic profiling, structural and cell biology to (1) identify the targets of the new KAI2ia-dependent volatile sesquiterpene signaling pathway; (2) perform structure-functional analysis of PhKAI2ia receptor and elucidate the molecular features that determine its substrate specificity/selectivity; and (3) determine whether the KAI2ia-dependent sesquiterpene signalling pathway operates via MAX2 ubiquitin ligase essential for karrikin signaling. This work will uncover yet unknown role(s) of KAI2is in plant VOC perception, illuminate KAI2ia-dependent signaling pathway from organismal to molecular levels and answer the question of how MAX2 ubiquitin ligases deliberate ligand-specific responses.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.