Metabolism

Karen Schumaker, PhD, understands that activities of living organisms require the performance of chemical, mechanical, osmotic or electrical work. The energy required for this work is supplied by metabolism, respiration, photosynthesis and fermentation. Adenosine triphosphate (ATP) has long been recognized as the universal energy currency, with metabolism supporting the synthesis of ATP and the hydrolysis of ATP being used for the subsequent work. However, ATP is not the only energy currency in living organisms. A second and very different energy currency links metabolism to work by a current of ions passing from one side of a membrane to the other. These ion currents play a major role in energy capture and they support a range of physiological processes from the active transport of nutrients to the removal of toxic ions. To more efficiently capture and utilize energy, it will be necessary to uncover mechanisms regulating these ion currents. In a project funded by the Physical Biosciences Program of the Office of Basic Energy Sciences at the Department of Energy, Dr. Schumaker asks how calcium-binding proteins regulate the activity of specific secondary active transporters to control cellular sodium ion homeostasis during plant growth in saline conditions.The build-up of salt in agricultural soils is a widespread problem that limits the growth and yield of important crop species worldwide. While genetic variation for plant growth in salinity (salt tolerance) exists, little is known about the genes and pathways underlying this variation. In a project funded by the Physiological and Structural Systems Cluster in the Division of Integrative Organismal Systems at the National Science Foundation, Dr. Schumaker’s lab analyzes the molecular evolution of the genes and associated networks that control plant adaptation to soil salinity. To do this, they are assessing the evolutionary forces acting on plant salt tolerance and mapping and isolating genes that underlie natural variation for this trait.

All viruses hijack host cell machinery to facilitate their replication. Producing infectious viral progeny relies on host cell metabolic pathways to provide energy and building blocks such as nucleotides, amino acids, and lipids. I am interested in investigating the molecular remodeling of cellular metabolic and lipid environments by viruses. The overall goal of my research in dissecting the complex virus-host metabolism interactions is to guide the development of novel antiviral therapies. Keywords: Infectious Disease, Virology, Metabolism, Lipidomics

Xianchun Li, PhD, is interested in understanding the physiological, biochemical, molecular and evolutionary bases of fundamental processes in the life history of insects such as embryonic polarity, metamorphosis, developmental commitment, host usage and environmental adaptation. One focus of his research is to elucidate the reciprocal signaling interactions between plants and insects, and the resulted on-going defense (in the case of plants) / counterdefense (in the case of herbivorous insects) phenotypic arm race over ecological time scale, with emphasis on the genetic machinery that percepts and transduces the reciprocal cues into genome and regulate defense / counterdefense phenotypes. Working systems include Helicoverpa zea, the corn earworm, a polyphagous noctuide of economic importance, and Drosophila melanogaster, the fruit fly, a model organism. State of arts and traditional techniques are combining to identify the cues and to uncover the signaling transduction cascade that links environmental cues, gene expression and the resulted defense/counterdefense phenotypes. This research may lead to characterization of genes for designing new insecticides and/or genetically modifying crops. The second focus of Dr. Li’s research is to define, globally, the regulatory triangle between nuclear receptors (NRs), their ligands, and cytochrome P450s (P450s) in Drosophila melanogaster. Nuclear receptors (NRs) constitute a transcription factor superfamily that has evolved to sense and bind endogenous (e.g., hormones) and/or exogenous (e.g., naturally-occurring or synthetic xenobiotics) signal compounds, resulting in differential expression of particular target genes, which underlies a range of fundamental biological processes, including growth, development, reproduction, behavior, host usage, and environmental adaptation. Many of those cue chemicals, namely NR ligands, are synthesized and/or metabolized by members of the P450s gene superfamily, whose expression may be regulated by certain NRs. Bioinformatics analyses as well as systematic functional genomic techniques such as microarray, X-ChIP, mutation and ectopic expression will be combined to define the genome-wide regulatory interaction loops between NRs and P450s as well as to assign, at least partially, functions of individual NRs and P450s in the life history of fruit fly. Given the evolutionary conservations of homologous NRs and P450s between vertebrates and invertebrates, the results obtained in this project are expected to provide insights into the reciprocal regulatory interactions between NRs and P450s in other animals including humans as well as to provide great insights into new avenue for human NR ligand identification and NR-related drug design. The third focus of his research is to investigate the molecular mechanisms of Bt and conventional insecticide resistance, which is a major threat in current IPM system. In collaboration with Dr. Bruce Tabashnik, Timothy Dennehy, and Yves Carriere in our Department, Dr. Li is going to compare Bt toxin binding affinity and other defects of natural (s, r1, r2, r3) and artificial mutant PBW (Pink Bollworm) cadherin proteins and thus define the key functional domains of PBW cadherin.