Valerie M. Williamson

Rev. 01/01/2020



Dr.  Williamson completed her undergraduate education at Northeastern University in Boston with a B.A. in Biology.  She worked for three years at the Institute of Marine Science at the University of Alaska, Fairbanks.  Dr. Williamson received a Ph.D. in biochemistry from the University of California, Davis, in 1978.  She was a postdoctoral fellow in biochemistry at the University of Washington before moving to the ARCO Plant Cell Research Institute in Dublin, CA, as a research scientist and laboratory leader.  It was while in this position that Dr.  Williamson developed an interest in plant resistance to nematodes.  She was appointed Assistant Professor in the Department of Nematology at UC-Davis in 1987, and rose to the rank of Professor in 1997.  

The Mi gene in tomato confers resistance to Meloidogyne arenaria, M.  incognita, and M.  javanica.  Dr.  Williamson initiated efforts to clone this gene immediately upon her appointment at UC-Davis, and completed the task in 1998.  It proved to be much more difficult than originally anticipated. Although Mi was mapped fairly rapidly to a 650 kb region of the short arm of chromosome 6, final mapping and cloning was impeded by the lack of polymorphisms in this region.  In the end, it turned out that there were two intact gene sequences within a 52 kb region, only one of which actually confers resistance. 

Since cloning Mi, Dr. Williamson and her colleagues have worked to characterize the gene and unravel the precise mechanism by which it confers resistance.  Mi belongs to a family of similar resistance genes that have conserved LRR, LZ, and NBS domains.  One of the unique discoveries that has come from the work on Mi is that, in addition to conferring resistance to Meloidogyne species, Mi also confers resistance to the potato aphid.  This will lead to research that may reveal similarities between aphids and Meloidogyne spp. that were previously undreamed of and (or) reveal multiple activities of the resistance gene product.  Such research will inevitably lead to a greater understanding of how Mi and similar resistance genes function.  Further, with knowledge of the sequence of Mi, the ability to alter specific portions of the sequence, and to then transform tomato and other plants, Dr.  Williamson and her colleagues are unraveling the function of a nematode resistance gene. 

Good science involves rigorously tested hypotheses about biological phenomena; great science does so with biological phenomena of great importance. There can be few questions in our science of nematology that are more important than how host resistance actually works.  Few scientists have made greater contributions to our understanding of host resistance than Dr. Williamson.  Her work will have a major impact on our science for many years to come. 

In 2004, the Society of Nematologists named Valerie Moroz Williamson Fellow of the Society.


Return to Prominent Nematologists Menu

Go to Nemaplex Main Menu