Virus resistance in transgenic plants that express cucumber mosaic virus satellite RNA

Plants infected with cucumber mosaic virus (CMV) (KIN strain) produce a mild mosaic disease on tobacco whereas infections of CMV with satellite RNA (strain Y) cause a severe yellow mosaic. Analysis of recombinant and mutant forms of satellite RNA identified a site (nucleotides 185/186) in the Y satellite RNA that affects the ability to induce the yellow mosaic in combination with CMV but not with tomato aspermy virus. The location of this site with respect to other mutations in the satellite RNA indicated that polypeptides, which may be encoded by the satellite RNA, have no role in induction of yellow mosaic symptoms. The symptom induction is therefore an effect of the satellite RNA on the host plant with the intervention of the helper virus. In the course of the mutation analysis of satellite RNA we detected several secondary mutations which arose in planta. Two of these were deletions of more than 80 nucleotides. Other forms of mutant satellite RNA were non-functional even though the modifications involved nucleotides completely within the large secondary deletions. These data imply complex intramolecular interactions in the satellite RNA.

Section: Discussionmentioning

confidence: 99%

“…TAV has only partial sequence homology (Habili & Francki, 1974b;Harrison et al, 1987) and no serological relationship with CMV (Habili & Francki, 1974a) but can replicate some isolates of CMV satellite RNA Harrison et al, 1987).…”

Section: Introductionmentioning

confidence: 99%

Cucumber mosaic virus satellite RNA (Y strain): analysis of sequences which affect yellow mosaic symptoms on tobacco

Jaegle¹,

Devic

Longstaff

et al. 1990

“…The presence of CMV satRNAs is associated with a general depression in the synthesis of CMV RNA, in particular of RNAs 1 and 2 more than RNAs 3 and 4 (Kaper & Tousignant, 1977;Mossop & Francki, 1979). However CMV and TAV differ as helpers ofCMV satRNA in that the presence of CMV satRNA is not associated with a differential depression of TAV RNAs 1 and 2, nor indeed with a general depression of TAV RNA synthesis (Harrison et al, 1987;Mossop & Francki, 1979; our unpublished results). The interaction of CMV satRNA with the ICR2 motif-including sequence would be the same for TAV RNA 2 and for CMV RNA 2 (Fig.…”

Section: Non-coding Regions and Regulatory Signalsmentioning

confidence: 99%

Nucleotide sequence of tomato aspermy virus RNA 2

Moriones¹,

Roossinck²,

García‐Arenal³

1991

RNA 2 of the V strain of tomato aspermy virus (TAV) consists of 3074 nucleotides and contains one open reading frame of 2487 nucleotides. Thus, it resembles RNA 2 of cucumber mosaic virus (CMV) strains Q and Fny (62 % identical to both), brome mosaic virus (42 % identical) and cowpea chlorotic mottle virus (40% identical). In comparisons between amino acid sequences, three different regions of similarity could be distinguished. These were the central part (amino acids 224 to 757 for V-TAV), which was most similar among the four viruses, and the N and C ends; sequences conserved among RNA polymerase species were found in the C half of the central part. Hydrophobicity patterns, and distributions of acidic and basic amino acids in the proteins encoded by V-TAV RNA 2, Q-CMV RNA 2 and Fny-CMV RNA 2 were very similar except at the extreme ends of the molecules. Structures that have been reported to act as regulatory signals for minus-and plus-strand synthesis were found in the 5' and 3' non-coding regions of the RNA.

“…This comparison shows that interference by the artificially derived pRNAs is about as effective as that of naturally occurring DI-RNAs. Gerlach et al (1987) and Harrison et al (1987) have demonstrated that the expression of satellite RNAs in transgenic plants can confer resistance to virus infection. Several barriers prevent widespread use of satellite RNAs for induction of virus resistance.…”

Section: Discussionmentioning

confidence: 99%

“…This property has been exploited in transgenic plants by expressing satellite RNAs from nuclear genes, rendering plants resistant to infection with tobacco ringspot virus (Gerlach et al, 1987) and cucumber mosaic virus (Harrison et al, 1987). However, the use of satellite RNAs has three limitations: (i) most plant viruses do not have satellite RNAs, (ii) satellite RNAs are contagious agents with efficient packaging mechanisms and, most importantly, (iii) satellite RNAs often aggravate the severity of the symptoms of a virus infection (Murant & Mayo, 1982;Francki, 1985); a satellite RNA that alleviates the symptoms in one plant host may aggravate them in another.…”

Section: Introductionmentioning

confidence: 99%

Artificial Defective Interfering RNAs Derived from Brome Mosaic Virus

Marsh

Pogue

Connell

et al. 1991

Naturally occurring defective interfering RNAs (DIRNAs) greatly reduce the accumulation of their helper virus in vivo, but are rarely associated with plant positive-strand RNA viruses. Deletion mutants pRNA-2 M/S and pRNA-2 E/S, derived from brome mosaic virus (BMV) genomic RNA-2, replicated in a manner dependent on BMV RNA-1 and -2, and effectively interfered with their accumulation in barley protoplasts. Based on their mode of replication, these mutant RNAs have been termed parasitic RNAs (pRNAs). When present with RNA-1 and -2 at low inoculum amounts, pRNA-2 M/S and pRNA-2 E/S reduced the level of replication of RNA-2, the parental RNA, by 37 % and 64 %, respectively. Greater amounts of pRNA in the inoculum completely eliminated the replication of both RNA-I and -2. Mutations that prevented translation of truncated proteins from the pRNAs did not affect interference, but those that reduced pRNA replication decreased their ability to interfere with genomic RNA replication. At a molar pRNA: genomic RNA inoculum ratio of 1.5: 1, pRNA-2 E/S reduced the accumulation of all helper virus RNAs by > 60%. This occurred in the presence of wild-type RNA-3 or ASGP RNA-3, a deletion mutant of RNA-3 that lacks the subgenomic promoter necessary for coat protein expression, demonstrating that the interference mediated by the pRNAs was not effected by encapsidation. These data indicate that the expression of pRNAs that function as artificial DIRNAs in transgenic plants may be an approach for inducing resistance to virus infection which is applicable to a wide range of plant viruses.