Title : Understanding of the Molecular Plant-Virus Interactions and development of Novel Antiviral Strategies
Abstract:
Plant viruses are obligate intracellular parasites that infect many agriculturally important crops and cause severe losses each year. Genetic resistance is considered the most effective means to control these viruses. However, extensive screening of germplasms for natural genetic resistance only identifies a few resistance (R) genes. Due to the frequent occurrence of resistance breaking isolates, the resistance conferred by these R genes is often not durable. To develop novel antiviral strategies, we have employed classical molecular and biochemistry tools as well as cutting edge technologies to study molecular virus-plant interactions. Since potyviruses are the largest group of known plant viruses including a number of notorious viruses such as plum pox virus (PPV), turnip mosaic virus (TuMV), soybean mosaic virus (SMV), potato virus Y (PPV) and papaya ringspot virus (PRV), we chose potyviruses as our major research target. We have been concentrated on the molecular identification of host factor genes that are essential for infections by TuMV, PPV and SMV, and functional characterization of their roles in the infection process. We have identified over ten host factor genes and conducted proof-of-concept experiments in manipulation of them for disease control using PPV as a case study. In collaboration with colleagues, transgenic plum highly resistant to PPV was successfully developed by targeting either the PPV genome or the plum eIF(iso)4E gene, a host factor gene of PPV. Since peach, the primary host of PPV, is recalcitrant to genetic transformation, established technologies such as precise genome editing and RNA silencing (RNAi) that require genetic transformation are not applicable. We thus studied the possibility to create PPV resistance by silencing a host factor gene of PPV through virus-induced gene silencing (VIGS) as well as by generation of a peach mutant population for screening for target gene mutants. For the VIGS approach, we found that Prunus necrotic ringspot virus (PNRSV) was highly endemic on stone fruit trees in Canada, and no obvious phenotypic differences were observed among PNRSV-positive or negative trees. We developed a PNRSV-based vector and further modified the vector to target the eIF(iso)4E gene. This modified vector knocked down the expression of eIF(iso)4E and prevented PPV infection in peach. The modified PNRSV vector is ready for field test. For the mutagenesis approach, we have developed a novel protocol to generate peach mutants and developed a peach mutant population consisting of more than 2,000 lines. Our current research focus is on screening for and molecular characterization of peach mutants resistant to PPV.
