Cross-protection and heterologous encapsidation among barley yellow dwarf viruses

Fujiang Wen, Purdue University

Abstract

Enzyme-linked immunosorbent assay (ELISA), dot blot hybridization, and immunohybridization were used to investigate various interactions either among barley yellow dwarf viruses (BYDV) or between BYDV and brome mosaic virus (BMV) in mixed infections. These interactions included cross protection, heterologous encapsidation, and enhanced production of BYDV in mixed infections. Generally, the degree of cross protection was consistent with serological relatedness of the BYDV isolates. The more related the isolates, the higher was the degree of cross protection. Various degrees of cross protection occurred with any two of the isolates MAV-NY, MAV-PS1, P-PAV, and SGV. Cross protection did not occur with other pairs of isolates. With longer time intervals between inoculations of paired viruses, the cross protection effect was more persistent. In oat plants mixedly infected with RPV and either MAV-PS1 or P-PAV, apart from homologous encapsidation, some of the viral RNAs of either P-PAV or MAV-PS1 were encapsidated in the protein capsids of RPV, but there was no evidence of such encapsidation of the RNA of RPV in the protein capsids of either P-PAV or MAV-PS1. By contrast, in plants mixedly infected with P-PAV and MAV-PS1, viral RNAs of P-PAV and MAV-PS1 were detected by specific cDNA probes in virions trapped with MAV-specific and PAV-specific antibodies, respectively. Further analysis of immuno-precipitated samples by immunohybridization demonstrated that transcapsidation was the predominant type of heterologous encapsidation between RPV and either P-PAV or MAV-PS1, while phenotypic mixing was the predominant type of heterologous encapsidation between P-PAV and MAV-PS1. Interactions in mixed infections between BYDV and BMV were investigated to see if synergistic effect occurred in mixed infections. Mixedly infected plants showed more severe symptoms than singly infected plants and RPV content was enhanced about two-fold in plants mixedly infected with RPV and BMV, although production of either P-PAV or MAV-PS1 was not consistently enhanced in mixed infections with BMV. BMV content was not significantly enhanced in mixed infections. Tests with fluorescent antibodies indicated that the enhanced RPV production was unlikely to be due to the invasion of mesophyll cells by RPV. There was no evidence of dependent transmission of either BMV or BYDV from the mixed infections.

Degree

Ph.D.

Advisors

Lister, Purdue University.

Subject Area

Plant pathology

COinS