Mutational analysis of potato yellow mosaic geminivirus

Abstract

Mutations have been inserted into the virion and complementary sense ORFs encoding proteins with MrS in excess of 9 kDa of both DNA A and DNA B of potato yellow mosaic geminivirus (PYMV). Wild-type and mutant monomeric clones were tested for their ability to replicate, produce PYMV-specific DNA, spread and cause symptoms in Nicotiana benthamiana plants following biolistic inoculation. Dimeric clones of the DNA A mutants were also investigated by agroinoculation of leaf discs. In contrast to N. benthamiana plants agroinoculated with PYMV DNA A, in which the wild-type DNA A component was capable of limited independent replication and spread, both excised DNA A and B components were required for DNA replication and symptom development in plants inoculated by the biolistic method. Mixtures of both genomic components were also infectious for potato plants following biolistic inoculation. Mutations in ORFs ALl, AL2, BR1 and BLl resulted in clones incapable of infecting N. benthamiana plants. However, the AL2 mutation, but not the ALl mutation, allowed viral DNA replication in leaf discs. Mutations to both the ARI and AL30RFs produced clones which were infectious in plants but showed a considerable delay in the production of attenuated symptoms as compared to wild-type infections. Mutating the AL30RF dramatically reduced viral DNA replication in both whole plants and leaf discs. Mutations to the AL40RF produced clones which were as infectious for both N. benthamiana and potato plants as the wild-type clones. Our results are compared with those from mutagenesis studies on related bipartite geminiviruses.

Potato yellow mosaic geminivirus AC2 protein is a sequence non‐specific DNA binding protein

“…Mutagenesis of TGMV illustrated that the AC2 ORF was r~'quired for symptom formation in whole plants but not viral I~NA replication in agroinoculated leaf discs [8] and the same r,~sult was found for PYMV [6]. The AC2 gene product of sttbgroup III geminiviruses can complement mutations in hete;ologous viral genomes both in protoplasts [10] and in plants [ i 1,12].…”

Pseudorecombination and complementation between potato yellow mosaic geminivirus and tomato golden mosaic geminivirus

“…Recent genetic analysis has shown that the organization and function of the ORFs in PYMV and TGMV are similar * Author for correspondence. Fax +44 171 584 2056. e-mail r.coutts@ic.ac.uk (Sung & Coutts, 1995) and places the two viruses in the same phylogenetic cluster (Arguello-Astorga et al, 1994;Faria et al, 1994;Fontes et al, 1994a, b;Padidam et al, 1995). The DNA A components of both viruses encode all of the viral information necessary for replication [the AC 1, protein] and encapsidation (the AV1, coat protein) of both DNAs (Rogers et al, 1986;Sunter et al, 1987;Sung & Coutts, 1995).…”

“…Fax +44 171 584 2056. e-mail r.coutts@ic.ac.uk (Sung & Coutts, 1995) and places the two viruses in the same phylogenetic cluster (Arguello-Astorga et al, 1994;Faria et al, 1994;Fontes et al, 1994a, b;Padidam et al, 1995). The DNA A components of both viruses encode all of the viral information necessary for replication [the AC 1, protein] and encapsidation (the AV1, coat protein) of both DNAs (Rogers et al, 1986;Sunter et al, 1987;Sung & Coutts, 1995). The protein encoded by the AC30RF, while not absolutely required for viral replication, is necessary for normal accumulation of viral DNA in infected plants (Elmer et al, 1988;Sung & Coutts, 1995) and protoplasts (Sunter et al, 1990).…”

“…The DNA A components of both viruses encode all of the viral information necessary for replication [the AC 1, protein] and encapsidation (the AV1, coat protein) of both DNAs (Rogers et al, 1986;Sunter et al, 1987;Sung & Coutts, 1995). The protein encoded by the AC30RF, while not absolutely required for viral replication, is necessary for normal accumulation of viral DNA in infected plants (Elmer et al, 1988;Sung & Coutts, 1995) and protoplasts (Sunter et al, 1990). The AC2 gene product transactivates transcription of the TGMV AV1 and BV1 genes (Sunter & Bisaro, 1991.…”

“…The AC2 gene product transactivates transcription of the TGMV AV1 and BV1 genes (Sunter & Bisaro, 1991. The B components (encoding the BV1 and BCI proteins) provide functions necessary for efficient systemic spread in infected plants (von Arnim & Stanley, 1992;Sung & Coutts, 1995).…”