Coat Protein Transgene Research Articles

A coat protein transgene from a Scottish isolate of potato mop-top virus mediates strong resistance against Scandinavian isolates which have similar coat protein genes

Resistance tests were made on seedlings of transformed lines of Nicotiana benthamiana which contain a transgene encoding the coat protein (CP) gene of a Scottish isolate of potato mop-top virus (PMTV). This transgene has been reported to confer strong resistance to the PMTV isolate from which the transgene sequence was derived and also to a second Scottish isolate. Plants of lines of the transgenic N. benthamiana were as resistant to two Swedish and two Danish PMTV isolates as to a Scottish isolate, and of five lines tested, greater than 93.5% of transgenic plants were immune. The coat protein gene sequences of these four Scandinavian isolates were very similar to those of the two Scottish isolates. The greatest divergence between the isolates was three amino acid changes and there was less than 2% change in CP gene nucleotide sequence. It is concluded that the PMTV CP transgene used in these experiments could confer resistance against isolates from different geographical areas because it is becoming apparent that the CP genes of PMTV isolates are highly conserved.

Host genes and transgenes that confer resistance to a Scottish isolate of potato leafroll virus are also effective against a Peruvian isolate

Potato genotypes with host gene-mediated resistance (host-MR) and coat protein-mediated transgenic resistance (CP-MR) to potato leafroll virus (PLRV), were inoculated with a Scottish and a Peruvian isolate of PLRV. The coat protein transgene had been cloned from the Scottish PLRV isolate which had also been used during the screening and selection of genotypes with host resistance. Significantly less PLRV accumulated in plants with either host-MR or CP-MR than in plants of susceptible genotypes or in non-transformed control plants, but the two forms of resistance were equally effective against both PLRV isolates.

Studies of Coat Protein-Mediated Resistance to TMV: I. The PM2 Assembly Defective Mutant Confers Resistance to TMV

Tobacco mosaic virus mutant PM2 contains two amino acid changes in coat protein sequence relative to the sequence of the coat protein of TMV U1. This results in unstable infectivity, inability to cause normal systemic infection, and accumulation of elongated open helixes of coat protein. Using site-directed mutagenesis we demonstrated that the characteristics of PM2 are due to the change of Thr28 → Ile, while the second change, Glu95 → Asp, had no apparent effect on virion structure or infectivity. Transgenic Nicotiana tabacum cv Xanthi NN and Xanthi nn plants that accumulate coat protein that contains one or both of the amino acid changes are as resistant to TMV infection as transgenic plants that contain wildtype TMV coat protein. The implication of these results on a model for coat protein-mediated resistance that involves the interaction of transgenic coat protein with the challenge virus is discussed.

Transgenic Burley and Flue-Cured Tobacco with Resistance to Four Necrotic Isolates of Potato Virus Y

Transgenic burley (cultivars KY14, NC3433-33, and TN90) and flue-cured (cultivar K326) tobacco with resistance to four necrotic isolates of potato virus Y (PVY) were constructed. These tobacco cultivars were transformed with a chimeric gene designed to express the coat protein (CP) from the necrotic Chilean isolate of PVY. CP expression among R 0 plants was undetectable by indirect enzyme-linked immunosorbent assay and Western blot (immunoblot) analysis. Transgenic R 0 plants that harbored from one to five neomycin phosphotransferase II (NPT II) transgene loci were identified. Although the NPT II and the PVY CP chimeric genes were linked within a common T-DNA, no correlation was found between the number of NPT II and CP transgenes. Inoculation of 41 independent transgenic KY14 R 0 plants with PVY-Chilean identified eight resistant plants, while inoculation of 30 transgenic K326 R 0 plants identified six resistant plants. Inoculation of 17 transgenic NC3433-33 R 0 plants with PVY-Chilean identified six resistant plants, while inoculation of 50 transgenic TN90 R 0 plants with PVY isolate VAM B resulted in nine resistant plants. Progeny derived from PVY-inoculated but symptomless R 0 plants were also resistant to the Chilean, Europe H, M s N r , N-Canada, and VAM B isolates of PVY, demonstrating sexual transmission of the transgenes that condition resistance. We discuss the ability of the PVY-Chilean CP gene to protect transgenic tobacco K326, KY14, NC3433-33, and TN90 from infection by four necrotic isolates of PVY. The flue-cured tobacco cultivar K326, which carries a gene simultaneously conferring resistance against root-knot nematode and susceptibility to PVY strain M S N R , is protected against this strain when transformed with the PVY-Chilean CP gene.

Nepoviruses—A Molecular Approach

ABSTRACTNepoviruses are an important group of plant viruses which can cause significant losses in the grapevine, soft fruit and walnut industries. This brief review discusses a molecular biology approach towards combating the nepovirus problem. Molecular techniques have been used to obtain the genome sequences of several group members. The organization of the virus genomes has been studies and the locations of open reading frames which encode a number of proteins, including the coat protein have been identified. Plants containing the coat protein transgene have been constructed and have been shown to be resistant to virus infection.

Coat protein gene-mediated resistance to potato virus Y in tobacco: examination of the resistance mechanisms--is the transgenic coat protein required for protection?

We transformed SR1 tobacco with a cDNA fragment of the potato virus Y strain N (PVYN) 605 genome which contained the 3' end of the NIb polymerase gene, the coat protein (CP) coding sequence, and most of the viral 3' untranslated region. Complete resistance to several PVY strains was obtained in plants of the R2 generation. The resistance to PVYN and PVYO strains was maintained when the plants were inoculated dually with the potato potyviruses V or A (PVV or PVA). Only partial resistance to PVYN 605 was observed in plants containing the CP coding sequence in an antisense orientation. Both the "sense" and "antisense" plants accumulated CP transcripts and possessed multiple copies of the transgene. Systemic spread of the virus was studied by grafting experiments. The transgenic PVYN 605 CP was undetectable in healthy plants. This protein accumulated in plants of PVY-susceptible CP-transgenic line 4B5-31 when infected by PVYO, PVA, or PVV, but not in plants of line 4B5-S4, that were resistant to PVY and tolerant to PVA or PVV. To assess the role of the transgenic PVYN 605 CP in protection, we transformed plants with a construct bearing a frame-shift mutation at the beginning of the CP coding sequence, and observed partial protection from PVYN 605. Several hypotheses to explain these resistance mechanisms are discussed.