Regulation and Function of Membrane Lipid Hydrolysis in Lipid-Mediated Signaling in Plants Grant proposal number: IOS-0818740 PI: Xuemin Wang
PROJECT SUMMARY
Cell membranes are rich sources for producing bioactive compounds that affect plant growth, development, and stress responses. This project investigates the molecular mechanism by which one class membrane lipid-hydrolyzing enzyme phospholipase D (PLD) and its product phosphatidic acid (PA) mediate plant survival, growth, and biomass accumulation. The central hypothesis is that specific PLDs and PAs mediate plant growth by interacting with proteins in carbon metabolism and translation regulation. This project will characterize the interaction of PLD/PA with one group of enzymes in carbon metabolism and another in translation regulation. The PA/PLD-effector interactions will be characterized using different approaches, including quantitative biophysical analysis and open-ended profiling of proteins and lipids in the regulatory complexes. The intellectual merits of the research are to discover direct connections of membrane-based signaling with energy metabolism and growth control and to identify novel regulatory processes in plants with potential to improve plant production.
The proposed activity will have broader impacts on science, education, and society. The proposed work has the potential to transform current knowledge on the molecular and biochemical mechanism by which cells integrate stress and growth cues for optimizing plant production. It will provide opportunities to train students and researchers in emerging, under-explored disciplines in plant biology. It will serve as a platform to broaden participation of underrepresented groups in research. The information will be disseminated to enhance science and education through lectures and seminars, classroom teaching, scientific meetings, and publications. The knowledge gained may be applicable to developing crop plants with enhanced stress tolerance and productivity.
Membrane lipids play vital roles not only in membrane structures, but also in cellular communications and regulation. Phospholipases catalyze lipid hydrolysis, and the activation of these enzymes constitutes an early, critical step in signaling cascades in plant growth, development, and stress responses. Phospholipase D (PLD) is a major phospholipase family in plants, and its lipid product phosphatidic acid (PA) have been proposed to mediate different plant processes, including plant response to drought, high salinity, and nitrogen availability. The goal of this project is to understand the molecular processes by which PLD and PA interact with cellular machinery to regulate plant stress response and production. The central hypothesis tested is that specific PLDs and derived PA mediate plant stress response and growth by interacting with proteins in carbon metabolism and translation regulation. Specifically, 1) the study has identified and characterized the PLD interaction with two cytosolic glyceraldehyde-3-phosphate dehydrogenases (Gap) involved in glycolysis and gluconeogenesis in Arabidopsis. It has showed that this interaction plays an important role in plant sensing of drought and oxidative stress. Abrogation of the interaction renders plants less responsive to water loss and thus plants continue losing water even under water deficit conditions. 2) This project has characterized PA interaction with phytoshingoshine kinases at the biochemical, genetic, and physiological levels. It has found that the two lipid signaling processes, PLD-mediated phospholipid hydrolysis and the sphingosine kinase-mediated lipid phosphorylation, form a positive regulatory loop promoting plant response to abscisic acid and water deficits. 3) The study identified that PA interacts with ribosomal protein S6 kinases that are involved in translation and cell growth. These data have established the interaction of PLD/PA with key components in carbon metabolism, cell signaling, and translation regulation. These findings indicate that the membrane lipid-based signaling provide a direct link between plant perception of water stress and alterations in energy metabolism and plant growth response. The research and education activities have broader impacts on science, education, and society. The results have advanced current knowledge on the molecular and biochemical mechanism by which plants integrate stress and growth cues for optimizing plant production. The research provided opportunities to train graduate and undergraduate students and postdoctoral researchers, as well as high school students, in emerging, under-explored disciplines in plant biology. It served as a platform to broaden participation of underrepresented groups in research. Minority and female students were recruited through national and on-campus programs, such as Students and Teachers As Research Scientists (STARS), Des Lee Scholarships, and NSF-REU. The work has enriched educational experience for students through partnerships between University of Missouri and Danforth Plant Science Center. The information has been disseminated to enhance science and education through lectures and seminars, in classroom teaching, at national and international meetings, and through timely publications in peer-reviewed journals. The mutant materials and methods developed have been made available to the research community. Knowledge gained from the study has been tested to develop crop plants with enhanced drought tolerance and productivity.
