Studies of coat protein-mediated resistance to tobacco mosaic virus (TMV). II. Challenge by a mutant with altered virion surface does not overcome resistance conferred by TMV coat protein

Abstract

Transgenic tobacco plants expressing the coat protein (CP) gene of the U1 strain of tobacco mosaic virus (TMV) exhibit CP-mediated resistance (CP-MR) against some, but not all, tobamoviruses. To investigate the role of the amino acid sequences on the surface of the challenge virus in CP-MR, mutant strains of U1 TMV were constructed to contain the amino or carboxy termini of the CP of Sunn hemp mosaic tobamovirus (SHMV). The modified virus was unable to overcome CP-MR in transgenic plants that contained the TMV CP. In contrast, TMV in which the CP was replaced by the SHMV CP overcame CP-MR to the same extent as did SHMV. We conclude that CP-MR conferred by TMV CP involves interactions between amino acid sequences of the challenge viruses and the transgene protein other than those on the surface of the challenge virus.Coat protein-mediated resistance (CP-MR) has been widely used to develop protection in monocots and dicots against a number of different viruses (see reviews by Fitchen & Beachy, 1993;Wilson, 1993). However, the molecular and cellular nature of the resistance has not been fully elucidated for any example of CP-MR. We have focused our studies of CP-MR on protection against tobacco mosaic tobamovirus (TMV) in tomato and tobacco plants. CP-MR conferred by the CP of TMV was highly effective against TMV and closely related tobamoviruses and less effective against the more distantly related Sunn hemp mosaic virus (SHMV; Anderson et al., 1989). The amino acid sequence of the CP of SHMV differs by about 60% from the CP sequence of TMV. It was proposed that the low level of amino acid sequence identity between the CPs of TMV strain U1 and SHMV contributes to the ability of the

Mechanisms of Pathogen-Derived Resistance to Viruses in Transgenic Plants

“…tent with an inhibition of (pseudo)virion disassembly (Osbourn et al, 1989). A third test of the disassembly hypothesis was the demonstration that transgenic expression of mutant and recombinant forms of the TMV CP conferred resistance to TMV (Clark et al, 1995a(Clark et al, , 1995b. This resistance was associated with the potential of mutant CP to interact with the CP subunits of inoculated wild-type virions.…”

Localization of Barley yellow dwarf virus Movement Protein Modulating Programmed Cell Death in Nicotiana benthamiana

“…Like P3/P5 in Polerovirus , that of BYDV is responsible for insect transmission and acts to facilitate long-distance virus movement in phloem tissue ( Taliansky et al, 2003 ). From many cases, viral CP has been known to the factor triggering resistant responses of host plants against viral infection ( Baulcombe et al, 1994 ; Beachy, 1999 ; Bendahmane et al, 1995 , 1997 ; Clark et al, 1995a , 1995b ; Deom et al, 1994 ; Lim et al, 1997 ; Osbourn et al, 1990 ).…”

When an Intruder Comes Home: GM and GE Strategies to Combat Virus Infection in Plants

“…For instance, if CP is expressed in mesophyll but the viral RNA is introduced in epidermal cells then resistance did not develop [75]. The expression of mutant CP in transgenics also resulted in a resistance against wild-type CP, as the mutant CP could interact with the wild-type CP subunits or the host factors, which were involved in virion disassembly [76,77]. The extent of the aggregation of the CP correlated with the level of the coat protein-mediated resistance (CPMR) [78].…”