Walter Gassmann

Portrait of Walter Gassmann in collared shirt and sweater

Ph.D.

Director

Bond Life Sciences Center

Professor

Division of Plant Science & Technology

Research at a glance

Area(s) of Expertise

Research Summary

Research in the Gassmann lab focuses on the plant innate immune system. In particular, interests include how the immune system is activated by pathogen-associated signals and how it is kept in check to prevent harmful side effects such as stunted growth and reduced seed yield that occur when the immune system is overactive. This builds on the discovery of new components of a plant’s immune machinery that contribute to tight control of immune and other stress responses.

Gassmann received his Ph.D. from UC San Diego in 1996 researching plant membrane transporters in the lab of Dr. Julian Schroeder. As a post-doctoral researcher in the lab of Dr. Brian Staskawicz, UC Berkeley, he cloned and characterized RPS4, one of the founding members of the Toll/Interleukin-1 Receptor – Nucleotide Binding Site – Leucine-Rich Repeat (TNL) class of plant innate immune receptors, that recognizes the presence of the bacterial effector protein AvrRps4. His lab at MU, which he started as an assistant professor in the Department of Plant Microbiology & Pathology in 2000, cloned the second antibacterial receptor of the same class, RPS6. His early work at MU focused on the fine-tuned regulation of RPS4 expression and function by alternative splicing of RPS4 transcripts. The reconstitution of RPS4 function by expressing a combination of constructs representing regular and alternative transcripts is one of the few direct demonstrations that alternative splicing has functional significance in plants.

The innate immune response triggered by TNL and related immune receptors is very potent at preventing pathogen spread. Consequently, this response also has the potential to be detrimental to the host if not regulated properly. Apart from the regulation of immune receptor expression and accumulation it is still unclear how this fine-tuning of the immune system is achieved. Gassmann addressed this gap in knowledge directly with a genetic screen for mutants with a narrowly defined upregulation of immune receptor signaling and isolated SRFR1, a negative regulator of plant immunity. Interestingly, SRFR1 is widely conserved between plants and other organisms, including humans. To date Arabidopsis SRFR1 is the only family member with an assigned function. How SRFR1 controls the immune system and other stress responses is an active research area in the lab.

The cultivation of genetically uniform plants over large areas frequently selects for pathogen strains that can overcome innate plant defenses, and large crop losses can ensue. While many examples of plants with constitutively active defenses with improved pathogen resistance are known, these usually are associated with biomass and yield reductions. It is therefore important to understand plant immune regulatory systems to ultimately generate plants with increased pathogen defenses in the absence of growth defects and yield penalties.

Educational background

  • Ph.D., University of California, San Diego, 1996
  • M.S. (Dipl. rer. nat.), Swiss Federal Institute of Technology Zürich, 1990

Courses taught

  • PLNT_SCI 8505: Plant Stress Biology
  • PLNT_SCI 9540: Genetics of Plant-Microorganism Interaction