ORF C4 of Tomato Leaf Curl Geminivirus Is a Determinant of Symptom Severity

Rigden, Justin E.; Krake, L. R.; Rezaian, M. Ali; Dry, Ian B.

doi:10.1006/viro.1994.1606

Cited by 112 publications

(66 citation statements)

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“…Recent work with TGMV-based expression plasmids in protoplasts (Gr6ning et al, 1994) and with the in vitro transcription of plasmid-generated TGMV RNAs (Th6mmes & Buck, 1994) suggests that the AL4 protein is produced in abundance, at least in vitro and may contribute to suppressing AL 1 protein synthesis. A putative movement function for the tomato yellow leaf curl geminivirus C4 (analogous to AL4) protein has been reported (Jupin et al, 1994) and a role in symptom severity for tomato leaf curl geminivirus ORF C4 has also been demonstrated (Rigden et al, 1994). Any putative in vivo function(s) of the equivalent PYMV AL40RF gene product remain to be established although this study suggests that the protein may not play an important role in either replication or symptom expression.…”

Section: Resultsmentioning

confidence: 76%

Mutational analysis of potato yellow mosaic geminivirus

Sung

Coutts²

1995

Journal of General Virology

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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.

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Section: Resultsmentioning

confidence: 76%

Mutational analysis of potato yellow mosaic geminivirus

Sung

Coutts²

1995

Journal of General Virology

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“…Also, under experimental conditions several TYLCV strains from the region were found to cause more moderate symptoms in tomato than does ToLCOMV (not shown). Indeed, studies have implicated the C4 proteins of monopartite begomoviruses as being determinants of both symptom development (Krake et al, 1998;Rigden et al, 1993Rigden et al, , 1994 and systemic movement (Jupin et al, 1994;Rojas et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

An unusual alphasatellite associated with monopartite begomoviruses attenuates symptoms and reduces betasatellite accumulation

Idris

Shahid

Briddon

et al. 2010

Journal of General Virology

163

120

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The Oman strain of Tomato yellow leaf curl virus (TYLCV-OM) and its associated betasatellite, an isolate of Tomato leaf curl betasatellite (ToLCB), were previously reported from Oman. Here we report the isolation of a second, previously undescribed, begomovirus [Tomato leaf curl Oman virus (ToLCOMV)] and an alphasatellite from that same plant sample. This alphasatellite is closely related (90 % shared nucleotide identity) to an unusual DNA-2-type Ageratum yellow vein Singapore alphasatellite (AYVSGA), thus far identified only in Singapore. ToLCOMV was found to have a recombinant genome comprising sequences derived from two extant parents, TYLCV-OM, which is indigenous to Oman, and Papaya leaf curl virus from the Indian subcontinent. All possible combinations of ToLCOMV, TYLCV-OM, ToLCB and AYVSGA were used to agro-inoculate tomato and Nicotiana benthamiana. Infection with ToLCOMV yielded mild leaf-curl symptoms in both hosts; however, plants inoculated with TYLCV-OM developed more severe symptoms. Plants infected with ToLCB in the presence of either helper begomovirus resulted in more severe symptoms. Surprisingly, symptoms in N. benthamiana infected with the alphasatellite together with either of the helper viruses and the betasatellite were attenuated and betasatellite DNA accumulation was substantially reduced. However, in the latter plants no concomitant reduction in the accumulation of helper virus DNA was observed. This is the first example of an attenuation of begomovirus-betasatellite symptoms by this unusual class of alphasatellites. This observation suggests that some DNA-2 alphasatellites encode a pathogenicity determinant that may modulate begomovirus-betasatellite infection by reducing betasatellite DNA accumulation.

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“…The third codon position of ORF C1 corresponds to the second codon position of ORF C4. Three independent studies using site-directed mutagenesis showed that mutations in ORF C4 that do not cause amino acid replacement in ORF C1 do change hostrange and/or disease severity (Stanley and Latham, 1992;Rigden et al, 1994;Jupin et al, 1994). Thus, it is highly probable that products of ORF C4 interact with defence genes of the host, although interaction might be indirect.…”

Section: Introductionmentioning

confidence: 99%

Molecular evolution of a host-range gene in geminiviruses infecting asexual populations of Eupatorium makinoi.

et al. 1998

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Asexual plants of Eupatorium makinoi is frequently infected with tobacco leaf curl geminivirus (TLCV). The host range of TLCV is narrow, and ORF C4 is considered to function as a host range determinant. Using this TLCV-Eupatorium system, we tested the expectation that the rate of amino acid replacements will be accelerated in ORF C4 if resistant genes of the host plants drive molecular evolution in ORF C4. ORF C4 is entirely contained within a longer ORF C1 encoding a replication protein. We analyzed 21 sequences containing ORF C4 and a part of ORF C1. While per-site number of synonymous substitutions exceeded that of replacements in ORF C1, per-site number of replacements exceeded that of synonymous substitutions in ORF C4. However, this excess of per-site replacement in ORF C4 was mostly explained by the overlap gene nature, because most synonymous substitutions in ORF C1 change amino acid of ORF C4. In conclusion, not positive but negative selection is a predominant mode characterizing molecular evolution of ORF C4.

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ORF C4 of Tomato Leaf Curl Geminivirus Is a Determinant of Symptom Severity

Cited by 112 publications

References 0 publications

Mutational analysis of potato yellow mosaic geminivirus

Mutational analysis of potato yellow mosaic geminivirus

An unusual alphasatellite associated with monopartite begomoviruses attenuates symptoms and reduces betasatellite accumulation

Molecular evolution of a host-range gene in geminiviruses infecting asexual populations of Eupatorium makinoi.

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