Melany Sacco


Photograph of Melanie SaccoPlant immune receptor function in disease resistance

Infection of plants by the many pathogens existing in the environment is typically prevented by a number of evolved mechanisms. Plants, however, do encounter host-adapted pathogens that are able to overcome these natural defense mechanisms and cause disease, with consequences for agricultural production. Plant resistance genes encode immune receptors that provide robust protection against specific host-adapted pathogens. Their usefulness in agriculture has been limited due to the difficulties involved in a) identifying resistance genes in plants with large, complex genomes, b) transfer of resistance genes from resistant plants into important susceptible cultivars by conventional breeding without loss of productivity traits, and c) the study of the function of the proteins encoded by resistance genes.

We are establishing a model system in our laboratory to study resistance of Nicotiana plant species to viruses of the Polerovirus genus. Our model plants have both resistant and susceptible plant cultivars that will assist in identifying the resistance gene (designated Rpo1) using genetic, molecular biology and biochemistry tools. Rpo1 activated a cell death response in leaves of resistant plants in the presence of a Polerovirus protein called P0. Our model system, once developed will allow us to investigate the following:

• the feasibility of transferring the Rpo1 resistance gene to susceptible cultivars or other species by genetic engineering.
• the involvement of other necessary proteins that are required for immune receptor protein function.
• how Rpo1 recognizes Polerovirus P0 protein and activates a signal that initiates plant defense responses.

We are approaching this research by 1) generating transgenic plants for transposon tagging to identify the Rpo1 gene, 2) mutagenesis of P0 proteins from three Poleroviruses to identify important amino acid residues for recognition and 3) investigating association of the Argonaute1 protein with Rpo1, a protein known to interact with P0.

Selected publications

Sacco, M. A., Koropacka, K., Grenier, E., Jaubert, M., Blanchard, A. Goverse, A., Smant, G. and Moffett, P. The Cyst Nematode SPRYSEC Protein RBP-1 Elicits Gpa2- and RanGAP2-Dependent Plant Cell Death. PLoS Pathogens 2009 5 e1000564

Sacco, M. A. and Moffett, P. Disease Resistance Genes: Form and Function Chapter 5 in “Molecular Plant-Microbe Interactions” 2009 CAB International, UK. Neuroscience Letters 2005 390 76-80

Bhattacharjee, S., Zamora, A., Azhar, M., Sacco, M. A., Lambert, L., and P. Moffett. Virus resistance induced by NB-LRR proteins involves Argonaute4-dependent translational control. The Plant Journal 2009 58 940-951

Rairdan, G. J., Collier, S. M., Sacco, M. A., Baldwin, T. T., Boettrich, T. and P. Moffett. The coiled-coil and nucleotide binding domains of the Potato Rx disease resistance protein function in pathogen recognition and signaling. The Plant Cell 2008 20 739

Sacco, M. A., Mansoor, S. and P. Moffett. A RanGAP protein physically interacts with the NB-LRR protein Rx and is required for Rx-mediated viral resistance. The Plant Journal 2007 52 82