ABSTRACT
Coat-protein (CP) hybrids between Cucumber mosaic virus (CMV) and Tomato aspermy virus (TAV) were engineered to analyse reported CP-associated differences between these viruses. CP portions delimited by aa 1-59, 60-148 and 149-219 were exchanged in all possible combinations within TAV RNA3. The seven possible chimeras were able to replicate in tobacco protoplasts to similar levels, but only those having residues 1-59 or 60-148 from CMV were infectious to tobacco plants, a common host for CMV and TAV, and formed stable particles. When most of the movement protein (MP) of TAV was substituted for that of CMV, infectivity of CP hybrids did not vary. No hybrid was able to infect cucumber plants, a host for CMV and not for TAV. Need for MP-CP compatibility could explain these results, but shows that MP-CP compatibility conditions the use of CP chimeras to map CP-associated differences between CMV and TAV.
Subject(s)
Capsid Proteins/genetics , Capsid Proteins/physiology , Cucumovirus/genetics , Cucumovirus/physiology , Capsid Proteins/chemistry , Cucumovirus/pathogenicity , Genetic Engineering , Plant Diseases/virology , RNA, Viral/genetics , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Species Specificity , Nicotiana/virology , Virulence/geneticsABSTRACT
ABSTRACT Previously, we demonstrated that Broad bean mottle virus (BBMV), a member of the genus Bromovirus, could accumulate RNA 2-derived defective interfering (DI) RNAs during infection. In this work, we study how host and environmental factors affect the accumulation of DI RNAs. Serial passages of BBMV through selected plant species reveal that, with low-multiplicity inocula, some systemic hosts (Vicia faba, Nicotiana clevelandii, and N. tabacum cv. Samsum) support DI RNA accumulation after the first passage cycle but other hosts (Phaseolus vulgaris, Pisum sativum, and Glycine max) do not. However, several passages with the high-multiplicity inocula can generate DI RNAs in pea plants. Local lesion hosts (Chenopodium quinoa, C. amaranticolor, and C. murale) remain free of the DI RNA components. The size of the de novo-formed DI RNAs depends on the host and on environmental conditions. For instance, broad bean plants cultivated in a greenhouse or in a growth chamber at 20 degrees C accumulated DI RNAs of 2.4 or 1.9 kb in size, respectively. A reverse trend was observed in pea plants. Lower temperatures greatly facilitated the formation of DI RNAs in broad bean and pea hosts after the first passage. The importance of these findings for the studies on DI RNAs are discussed.
