My research is focused on the signaling and metabolic mechanisms underlying plant interaction with the environment. My lab research has been particularly focused on three topics: glucosinolate metabolism, guard cell signal transduction, and plant pathogen interaction.

0000-0002-6690-7612

Project 1. Glucosinolate metabolism. Glucosinolates are a group of naturally occurring thioglucosides, present in Brassica plants (e.g., canola and cabbage). Glucosinolate degradation products display diverse biological activities, including defense against insects and herbivores, N/S nutrition and growth regulation. From a human perspective, glucosinolate metabolites account for the distinctive flavors of cabbage and condiments. Some of the metabolites such as isothiocyanates exhibit anticarcinogenic properties. The core glucosinolate pathway has been well studied in Arabidopsis. However, we know little about how the components in different pathways interact to produce plant phenotypes and traits. Nor do we know how different layers of molecular control work together. The lack of such fundamental knowledge is a major reason why plant genetic engineering has been largely unsuccessful. It poses a chronic problem for rational engineering of crops for better quality and defense. Research in this project is focused on characterizing the regulatory and metabolic networks involving glucosinolate metabolism using multidisciplinary approaches. We aim to identify protein and metabolite changes in response to perturbation of glucosinolate metabolism and to integrate the data into glucosinolate networks. The process of networking will generate new testable hypotheses concerning glucosinolate metabolic pathways and related pathways. The ultimate objective is to use the immense biosynthetic potential of plants as an efficient, environmentally friendly and renewable source of fine chemicals and pharmaceuticals.

Project 2. Guard cell signaling networks. Guard cells are highly specialized plant epidermal cells that enclose tiny pores called stomata. Stomatal movements control both uptake of carbon dioxide and loss of water, and thus play important roles in plant growth and acclimation to environmental stresses. The plant hormone abscisic acid (ABA) is a key indicator of drought stress. ABA induces stomatal closure via an intricate intracellular signaling network in guard cells, thereby promoting plant water conservation. It is our central hypothesis that protein redox modification and dynamic changes in key metabolites are critical regulatory mechanisms in ABA signaling. We are testing the hypothesis by pursuing: identification of guard cell proteins whose redox status is altered in response to ABA and determination of their specific redox-sensitive amino acid residues, quantification of ABA-induced changes in metabolites implicated in guard cell signaling, and integration of the new information into a dynamic model of ABA-induced stomatal closure. Accomplishing these objectives is significant because it will reveal novel components of ABA signaling networks and provide knowledge of regulatory mechanisms underlying stomatal movements that will help to develop crops with enhanced stress tolerance and productivity.

Project 3. Plant pathogen interaction. The study of pathogen response and defense in crop species is of essential importance as the applications are directly related to agricultural production. Pseudomonas syringae pv tomato (Pst DC3000) causes speck disease in tomato (Solanum Lycopersicum), a crop growing in large quantities in Florida and having both nutritional and economical value. The goal of this project is to take what is known about pathogen host interactions and observe in greater detail mechanisms that plants utilize in response to pathogen infection at the posttranscriptional levels, including protein expression, redox and phosphorylation/dephosphorylation switches. Understanding changes in protein expression as well as redox and phospho-switches will provide important insights into how plant response and resistance to pathogens are occurring. Further investigation into unique/novel proteins and regulations will advance our knowledge of plant defense against pathogens, and allow researchers to use biotechnology to prevent future bacterial speck disease outbreaks.

Interestingly, as we gain more and more knowledge, the above projects have become interconnected with each other. Glucosinolate metabolism plays a role in pathogen defense and affects stomatal movement, which serves as the first line of defense against pathogen invasion. In addition to hypothesis generation projects, another major part of my research program has been hypothesis driven, i.e., characterizing molecular, biochemical and physiological functions of specific genes and proteins identified by proteomics and metabolomics approaches. One of the projects has been focused on understanding the key steps in the methionine chain-elongation pathway, which directly connects methionine (primary) metabolism to glucosinolate (spealized) metabolism. Our integration of hypothesis generation and hypothesis driven research will ultimately lead to a holistic view of cellular networks and processes in plants and will create important stepping stones towards potential biotechnological applications in enhanced yield, bioenergy and defense.