Agroinfiltration is a versatile tool that facilitates comparative analyses of Avr9/Cf-9-induced and Avr4/Cf-4-induced necrosis.
The avirulence genes Avr9 and Avr4 from the fungal tomato pathogen Cladosporium fulvum encode extracellular proteins that elicit a hypersensitive response when injected into leaves of tomato plants carrying the matching resistance genes, Cf-9 and Cf-4, respectively. We successfully expressed both Avr9 and Avr4 genes in tobacco with the Agrobacterium tumefaciens transient transformation assay (agroinfiltration). In addition, we expressed the matching resistance genes, Cf-9 and Cf-4, through agroinfiltration. By combining transient Cf gene expression with either transgenic plants expressing one of the gene partners, Potato virus X (PVX)-mediated Avr gene expression, or elicitor injections, we demonstrated that agroinfiltration is a reliable and versatile tool to study Avr/Cf-mediated recognition. Significantly, agroinfiltration can be used to quantify and compare Avr/Cf-induced responses. Comparison of different Avr/Cf-interactions within one tobacco leaf showed that Avr9/Cf-9-induced necrosis developed slower than necrosis induced by Avr4/Cf-4. Quantitative analysis demonstrated that this temporal difference was due to a difference in Avr gene activities. Transient expression of matching Avr/Cf gene pairs in a number of plant families indicated that the signal transduction pathway required for Avr/Cf-induced responses is conserved within solanaceous species. Most non-solanaceous species did not develop specific Avr/Cf-induced responses. However, co-expression of the Avr4/Cf-4 gene pair in lettuce resulted in necrosis, providing the first proof that a resistance (R) gene can function in a different plant family.
Van der Hoorn
R A
RA
Laboratory of Phytopathology, Wageningen University, The Netherlands.
Laurent
F
F
Roth
R
R
De Wit
P J
PJ
D016960:Agrobacterium tumefaciens / Q000235:genetics*; D002963:Cladosporium / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D009336:Necrosis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics* / Q000502:physiology
C085987:AVR4 protein, Cladosporium fulvum; C109609:Cf protein, Lycopersicon esculentum; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; D010940:Plant Proteins; C073605:AVR9 protein, Cladosporium fulvum