Plant-Associated Microbes

In the School of Integrative Plant Science (SIPS) we are making breakthroughs in understanding how microbes and other organisms interact with plants leading either to beneficial interactions or disease.  The following examples illustrate some of the ways in which SIPS faculty are characterizing these interactions and using their findings to promote outcomes that enhance plant health and disease resistance

Exploring beneficial interactions with other organisms to more effectively promote plant health

Many associations between plants and other organisms provide significant benefits to agriculturally important plants. Symbiotic fungi and bacteria can enhance plant nutrition, soil microbes suppress disease, and interactions with insects and other organisms are are essential to pollination and/or seed dispersal.

  • Maria Harrison 's group studies arbuscular mycorrizhal fungi which form associations with the roots of flowering plants and provide plants with phosphate in exchange for other nutrients. Understanding the molecular interactions that underlie phosphate transfer and development of symbiotic interactions may reveal new strategies for optimizing nutrient transfer to the host plant
  • Teresa Pawlowska's group studies also studies arbuscular mycorrizhal fungi and how bacterial endosymbionts of the fungi contribute to the symbiotic relationship.
  • Eric Nelson's research group is identifying fungi and oomycetes in the soil and evaluating them for differential effects on desirable plants and weeds as a potential strategy for control of weeds and invasive plants.
  • Robert Raguso's research group studies how volatile plant chemicals influence behavior of insect pollinators and pests. By understanding the biosynthetic pathways responsible for production of these chemicals as well as the receptors and biochemical response pathways in insects, these interactions can be manipulated to promote plant growth and health.

Identification of virulence factors and their targets to uncover sources of susceptibility and resistance

Many disease causing microbes are highly co-evolved with their plant hosts resulting in an elaborate network of molecular interactions. By identifying virulence determinants and using them to uncover interacting plant factors, we can better understand what determines susceptibility and resistance.  Altering virulence determinants and plant targets with various technologies is an important strategy for disease control.

  • Adam Bogdanove's research group works on TAL effector proteins that are injected into host plant by pathogenic bacteria and activate expression of genes that determine susceptibility and resistance. By identifying new effectors and their target sequences in host plants, the targets can be genetically altered to promote disease resistance. TAL effectors are additionally being used as biotechnological tools for DNA modification.
  • Tom Burr's research group has identified virulence factors in bacterial pathogens of grape. Mutagenesis of factors required for colonization and movement has been used to produce biocontrol agents that outcompete the pathogen but do not themselves cause disease.
  • Michele Cilia's  group uses affinity purification and mass spectroscopy to identify factors in host plants and insect vectors that interact with viruses and bacterial pathogens during different stages of transmission and disease development.  Factors important for virus transmission can be targeted by genetic modification of RNA silencing
    Tomato leaves inoculated with different strains of P. syringae having different combinations of virulence factors
  • Alan Collmer's group works on Pseudomonas syringaes that produce a vast array of virulence factors. By selectively recombining these factors in a strain from which they have all been deleted, Collmer's group is understanding how these toxins and type III effectors work together to interfere with plant defense pathways.
  • Greg Martin's group collaborates closely with the Collmer group, identifying defense pathways and proteins in tomato that trigger resistance in response to pathogen cultivars.  By screening for variation in responses among different tomatoes, Martin's group is identifying novel sources of host resistance.
  • Xiaohong Wang's research group is identifying nematode virulence factors that promote parasitism in potato.  RNA-silencing of nematode parasitism genes may prove an effective strategy for generating resistant cultivars. 
  • Steve Winans' group investigates how diffusible chemical signals regulate virulence in many pathogens. Understanding the details of these regulatory mechanisms can point to novel strategies for interfering with cell-to-cell communication 

Mathematical models of pathogen populations and host-pathogen interaction provide valuable information for growers and policy makers

  • Bill Fry's research group focuses on changes in Phytophthera infestans populations that influence virulence and strategies for disease control. Development and refinement of the BlightPro decision support system (DSS) helps users improve their crop protection strategy.
  • David Schneider's group investigates how different variables such as the presence of multiple pathogen strains or multiple susceptible species influences models of disease progression
  • Michael Milgroom's group is is using molecular markers to characterize population structure of powdery mildew fungus on grape. This work is providing insights into patterns of disease spread worldwide.