Research Interests:
My research in the Kochian lab has mainly focused on the physiological aspects of ion uptake in plants. Over time the themes have evolved, starting with projects on K+, NH4+, NO3-, and H+ fluxes in maize, rice, and barley roots, using the vibrating probe to measure ion currents, liquid membrane ion-specific electrodes to measure ion fluxes, standard electrophysiology to measure membrane potentials, and radioisotopic flux analysis to look at net ion fluxes. I have also worked on the physiology of iron and copper uptake. Here, we took advantage of E107, a single gene mutant, to help elaborate the multistep processes of reduction and absorption of these two metals. E107 acts as if it has a functional Fe-deficiency even when grown under Fe-adequate conditions.
After a few years, the physiology of Al-tolerance became an important part of our research plan. Early projects focused on the roles of Ca 2+ and H+ fluxes in Al-tolerance, as well as the electrophysiological responses of plant roots to Al over time. These efforts helped elucidate the nature and localization of the plant’s response to aluminum in the rhizosphere. Major team research projects have included multiple screenings of maize association panels (277 diverse inbred lines with complex familial relationships and population structure) for quantitative trait dissection of Al-tolerance. Here we used relative root growth and root tip Al content to quantify the responses. In addition, we have grown thousands of plants and collected their root tips for the analysis of protein expression in Al-tolerant and sensitive maize varieties. Currently, we are starting a similar project using a sorghum association panel, as well as evaluating at selected maize and sorghum lines from Kenya.
I also have worked extensively on measuring organic acid exudation (citrate, malate, oxalate) from roots using capillary zone electrophoresis. In some plants, organic acid exudation is an Al-tolerance mechanism. Part of the effort has been to improve the techniques of collecting the root exudates and in measuring organic acids with capillary electrophoresis (CE). This has been especially helpful in resolving organic acid content in very small samples (< 5 µL), maximizing CE system sensitivity, collecting exudates over short time periods and from root segments, and improving peak separation with exudate samples collected from Arabidopsis roots.
Throughout my tenure in the Kochian lab there have been many opportunities for methods and equipment development, something that I enjoy very much. For example, I have designed and fabricated uptake apparatuses for radioisotopic flux analysis, improved ion-specific electrode configuration, reformulated and synthesized liquid membrane sensors for ion specific electrodes, constructed root exudation systems, optimized exchange resin mixes and buffers for capillary electrophoresis analysis, and built specialized hydroponic systems. I worked with another technician to create a method by which we could measure short-term root growth.
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