FUNCTIONAL GENOMICS OF CEREAL DISEASE DEFENSE
Location: Corn Insects and Crop Genetics Research
Title: Construction of Coexpression Networks to Explore Barley-Powdery Mildew Interactions
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: March 20, 2008
Publication Date: July 1, 2008
Citation: Moscou, M.J., Caldo, R.A., Lauter, N.C., Wise, R.P. 2008. Construction of Coexpression Networks to Explore Barley-Powdery Mildew Interactions. In: Lorito, M., Woo, S.L., Scala, F., editors. Biology of Plant Microbe Interactions: The Impact of "omics." Volume 6. St. Paul, MN: APS Press. p. 113-117.
The interactions between an obligate biotrophic fungus and its plant host could be characterized as a counter-balancing act; as the fungus attempts to maximize nutrient siphoning and colonization, the host aims to restrict nutrient loss while minimizing the cost of defense. To establish biotrophy, the fungus must penetrate cell walls and construct haustorial feeding structures. To survive and reproduce, the pathogen must keep the tissue it has invaded alive and photosynthetically productive. Plants initially activate basal defenses to limit penetration and haustorial development, but typically resort to defenses that aim to starve the invaders. These range from local programmed cell death to rapid senescence of entire leaves. As such, it appears that plants are able to deploy defenses incrementally, allowing them to mount a sufficient but not unnecessary response. By contrast, pathogens may attempt to maximize biotrophy by capitalizing on the host’s resource expenditures for defense.
Recent studies in nonhost resistance, as well as host susceptibility, indicate that genes other than those governed by Resistance-Avirulence interactions also play key roles. Accordingly, we were also interested in identifying pathways where the pathogen co-opts networks, proteins, or metabolites that are synthesized by the host. In order to identify genes in such pathways, we constructed a coexpression network using time-course data collected from nine barley genotypes. Three criteria were used: (1) differential expression upon contact with the pathogen, (2) conserved expression with other genes (clusters) within a genotype, and (3) gene clusters that are conserved in their coexpression across all genotypes, regardless of wild-type or mutant status. Here we report our characterization of several sub-networks containing genes involved in sugar transport, photosynthesis, signaling, protein secretion, signal peptide processing, and abiotic stress signaling.