Dr. Loretta Johnson

Division of Biology
Departmental Website

Lead in our environment—from contaminated water pipes, mining or industrial activities—affects an organism’s DNA, how genes are expressed, and how DNA is repaired. Lead exposure may be involved in brain, stomach, and lung cancers. Populations that have long-term exposure to lead undergo changes in their DNA and in how their genes are controlled. We study how certain plants, after generations of growth in a former lead-contaminated mine site, may change over time to better tolerate higher lead levels and even absorb high levels of lead in their roots and leaves.

Our work focuses on the genetic changes that allow these plants to grow in heavily polluted areas and whether these changes involve differences in DNA itself and how the DNA is controlled. We study genetics and physiology of Andropogon virginicus, a weedy, perennial grass known as broomsedge, growing in mine sites of the Tar Creek Superfund Site in the Tri-State Mining Area of Kan., Okla., and Mo. We compare mine populations of broomsedge to non-mine populations to investigate if mine populations are genetically different. So far, we have found 50 genetic differences, two of which are related to metal binding and may protect the plants from lead poisoning. Similarly, humans exposed to long-term elevated levels of arsenic (another heavy metal) in water have genetic differences that increase their arsenic tolerance compared to the general population. We will also work with geneticists to study how lead affects DNA, contributes to the development of cancer, and alters the biology of plants and animals. This research will support the development of an NIH-funded Superfund Research Center.