Testimonials for Pioneer Member Charles Sam Levings, III

Steven Paul Briggs – Sam Levings brought molecular genetics to the study of plant immunity. In two landmark papers (PNAS 1987; Science 1988), Sam showed that variation in the maize mitochondrial genome caused both male sterility and susceptibility to a devastating fungal disease caused by Bipolaris maydis race T. At the time that Sam’s papers on URF13 were published, many investigators were striving to isolate and characterize nuclear genes that conferred disease resistance in plants. Sam’s work was an inspiration to me and he offered valuable advice and encouragement that helped us isolate and characterize the maize gene, Hm1, which confers resistance to a related fungus, now known as Cochliobolus carbonum race 3. Sam was an important community builder and he contributed substantially to establishing a collegial and rigorous culture amongst investigators working on crop immunity.

Brian Larkins – Although Sam was trained as a quantitative geneticist and maize breeder, he realized he would never explain the basis of maize cytoplasmic sterility using that approach. So, he taught himself to clone and sequence DNA. Through this approach he solved the basis of maize T-cytoplasmic male sterility and the basis of Southern corn leaf blight. Sam’s approach was a catalyst for molecular genetic approaches in agricultural research, and contributed to a paradigm shift in the way the agricultural industry approached research. Also, as Sam liked to say, “he was a really good guy”. He was an example and an inspriation to many of us.

Anne Schuster – Scientist; mom; community volunteer for education and sustainability; politician; artist; farmer. That was my life’s progression. I was an incredibly shy child and adult. I gradually morphed into an outspoken politician in the service of good. Sam helped give me confidence towards this life progression. I grew up in Nebraska and did my Ph.D. at the University of Nebraska in 1982 with Eric Davies in Plant Physiology. Brian Larkins did his Ph.D. in the same lab. We were jokingly ‘science siblings’. I was infatuated with molecular biology but was basically on my own in Nebraska. I spent a week in Brian’s lab at Purdue learning to isolate RNA that wasn’t chewed to bits by ribonucleases. I became a postdoc in Sam Leving’s lab four decades ago, 1982-84. It was my first experience in a really big lab. It hummed, or maybe vibrated. I loved it. I felt like I couldn’t learn or experience enough. Sam was a great role model. He obviously thrived in his world: strategizing, planning, organizing, teaching, learning. He let others determine the path they wanted to take and sat back and watched, offering guidance if needed. I had many failures. But two relatively simple things that I recall really caught his attention and he was surprised by me. One, I found an error in a Methods in Enzymology article (not published by him). The other was a formaldehyde gel I’d run of mitochondrial RNAs from Normal, C, S, T cytoplasms of male sterile, or not, maize. I had left the film to dry and he saw it when he came in early, as usual. There was a band of small single-stranded RNA in the S sample that was as abundant as a ribosomal band. What the heck? But, I had walked into a DNA lab. DNA sequencing was in full operation—primitive compared to today—reading sequences off X-ray films. Because of the intense DNA focus, RNA took a back seat and so not much came from my discovery. Today it might be a different story! The one odd thing we did discover was that it hybridized to a double-stranded RNA in a sample of LBN mitochondrial RNA studied by Paul Sisco, another postdoc. At the time, we never found out what the significance was. I had to return to Nebraska for personal reasons so could not pursue this line of science. Now it appears the RNAs may be autonomously replicating plasmids—perhaps small interfering RNAs as described by another lab years later. The impacts Sam had on me were numerous. I loved the old man. He opened up my world. He taught me what a scientific lab could be. His lab was full of a diverse group of people who collaborated and taught each other, had fun while doing so, and celebrated each other’s successes. He created this culture where you wanted to be, and, be included. Plus, he was a jokester. He was always teasing someone. That was infectious. Sam was so smart and insightful. He was always thinking. (Although my RNA probably bored, and so, confounded him. It would have meant pivoting to a whole new direction.) He did connect me with Bill Dougherty who ran the lab down the hall. Unfortunately, he couldn’t help but we developed a collegiality which lasted to our mutual stays at Oregon State University. Given a choice I would have remained in Sam’s lab for a long time. I have never felt so happy and fulfilled as a scientist. As it was I returned to Nebraska and after a bout of depression for losing what felt like a fast track, I got on another fast track with Jim Van Etten studying Chlorella viruses with their own restriction-modification enzyme systems. I got accomplished at DNA. Following this, I was a research associate in Russ Meints’s lab. One of our Ph.D. students, Ken Korth, became a postdoc with Sam so the connection was not lost.

Dilip M. Shah – I left my home country, India, in 1971 and arrived at the North Carolina State University (NCSU) to begin my career in science. I joined Dr. Sam Levings’ lab in the Department of Genetics as one of his first graduate students. During my first years in the US, I was completely naive about the American culture, its education system, and research enterprise. Dr. Levings guided me during my first two very challenging years with my course work and starting my research on corn organelle DNA. He explained cytoplasmic male sterility in corn and how the crop carrying Texas type (T)-cytoplasm was decimated by the fungal pathogen, Helminthosporium maydis, in the early 70’s. He asked me to determine if there was a defect in the mitochondrial DNA (mtDNA) of maize T cytoplasm relative to that of the normal cytoplasm. Dr. Levings was a quantitative geneticist by training and thus getting into molecular biology was itself a very bold move for him. He spent countless hours with me on my project, which led to the isolation of mtDNA from normal and T-cytoplasm corn. Based on the early work on the mtDNA of animal systems, the dogma at that time was that plant mtDNA was a small single circular molecule. However, this dogma was quickly proven wrong. Through electron microscopy studies, we discovered that corn mtDNA was very heterogeneous, comprising circular and linear molecules of different sizes. Although it proved quite difficult for Dr. Levings to convince the scientific community that plant mtDNA was quite different from that of animal mtDNA, he ultimately prevailed. Through several years and a tremendous amount of elegant work by graduate students and postdocs in his lab, he ultimately deciphered the molecular basis for cytoplasmic male sterility of T-cytoplasm in corn. Dr. Levings was a very inspiring mentor. He came to the lab very early each morning in his black Chevrolet pick-up. He took me to the corn field in his van several times and taught me how to pollinate corn and make genetic crosses. He helped me with much of my lab work aimed at characterizing what turned out to be an extremely complex plant mtDNA. I remember vividly him teaching me how to run a large and complex Model E analytical ultracentrifuge to determine the density of mtDNA. He played a key role in my training as a molecular biologist. I consider myself extremely fortunate to have had this smart and highly ambitious scientist as my Ph. D. advisor. He was a compassionate and caring mentor who made me feel at home. He also had a keen sense of humor. He will always be remembered as the great scientist and mentor who played a major role in shaping my career and those of many of his graduate students and postdocs. I cannot be more proud to have this opportunity to write this testimonial about him.

Charles Stuber – I first met Sam when I was a graduate student at N.C. State University and he was a post doc. Early on, I was impressed with his brilliant mind and how (early in his career) he switched from research in quantitative genetics to research in plant molecular biology. He made numerous very significant contributions to the understanding of mitochondrial genetics in maize. One of his most important contributions was the identficaion of the mitochondrial gene associated with the susceptibility of maize to a fungas that causes the very devastating disease, southern corn leaf blight. The value of his research to the corn industry is probably in the billions of dollars.