Christoph Benning - US grants

plants; lipids; enzymes; biomedical resource; biological products; bacteria;

The basic knowledge generated under this project will inspire novel strategies to produce more resilient crop plants that can better cope with a rapidly changing climate. During millions of years of evolution, plants have established the ability to live on land in a fluctuating environment, encountering harsh environmental conditions such as cold, drought, nutrient shortage, pathogen attack, insect outbreaks, or other abiotic or biotic stresses. To combat these challenges, sessile plants resourcefully adjust their internal biological processes, for example by shifting their metabolism from growth to defense. The project explores the interplay of two plant hormones, abscisic acid (ABA) and jasmonic acid (JA), in mediating responses to abiotic and biotic stresses, respectively. The latter originates from membranes in the chloroplast, the place of plant photosynthesis. This project has the potential to discover novel signaling molecules and mechanisms and their modifiers, thereby increasing our understanding of the integration of biotic and abiotic stress responses beyond our current knowledge about the roles of individual signaling molecules. The concepts and techniques of this project offer an exciting experimental platform for studying the integration of biotic and abiotic stress responses that are readily accessible to scientists at all training levels. The project is ideally suited for undergraduate student involvement in a classroom setting as well as through in-lab participation exposing them directly to ongoing real-life research, while teaching them basic scientific principles. A laboratory course, namely a Course-based Undergraduate Research Experience (CURE), has been developed to engage students in the isolation of project-relevant plant mutants and their initial characterization. Individual undergraduate students are involved in the deeper characterization of specific mutants in a research lab environment under the direct mentorship of the participating postdoctoral researchers, who in turn gain mentoring experience preparing them for their next stages in their careers.<br/><br/>Chloroplasts are dynamic organelles characterized by an extensive photosynthetic membrane with unique lipids and often respond to biotic and abiotic stresses by lipid remodeling. Lipid turnover in response to external cues often involves the release of acyl groups. These can be further converted into signaling mediators such as JA, divinyl ethers, aldehydes, or other molecules, which can be perceived by plants and trigger plant responses. In many instances, lipases with their lipid hydrolytic activity catalyze the first reaction during lipid remodeling, leading to the initiation of acyl group recycling, when plants are facing insults such as nutrient deprivation, cold, or heat. The project is based on recently characterized plastid lipases, PLIP1-3, from Arabidopsis. Overexpression of the respective coding sequences redirects the metabolism from growth to defense by initiating the biosynthesis and overproduction of oxylipin metabolites such as JA. Loss of PLIP1-3 function triple mutants show sensitivity to ABA. Moreover, the expression of two of the genes, PLIP2 and PLIP3, is responsive to abiotic stressors and ABA, suggesting a possible PLIP2,3-based mechanism in connecting JA and ABA signal transduction pathways in Arabidopsis. Although JA production is most commonly induced by biotic stressors such as wounding due to herbivorous insects, and ABA production is mainly increased by abiotic challenges such as cold, heat, or dehydration, there is increasing evidence of interaction of these signaling pathways as abiotic stressors can stimulate JA biosynthesis and JA can affect the sensitivity of the plant to ABA. The long-term goal of the project is to gain a deeper understanding of how chloroplast membrane lipid-derived signals are produced, transported, perpetuated, perceived, and integrated with different signaling pathways in Arabidopsis to coordinate biotic or abiotic stress responses. To accomplish this goal, the project follows three objectives: 1. Using a genetic suppressor screen in the PLIP3-OX (PLIP3 overexpression) background, the entire information chain from the origin of the lipid-based signal to its perception, transduction, and modification by other signaling pathways is being queried. 2. Suppressor loci are identified by bulk sequencing analysis of segregating suppressor mutant populations. 3. Individual suppressor mutants and affected proteins are characterized for their roles in JA biosynthesis, signaling, and modification by other signaling pathways. Objective 1 and partially objective 2 are conducted by undergraduate students in a classroom setting. Objective 3 involves individual undergraduate students under the mentorship of the participating postdoctoral researchers.<br/><br/>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.