Studies on the Tm-1 gene of tomato and host specificity of tobamoviruses

Abstract

Tm-1 is a semidominant resistance gene of tomato to the tobamovirus Tomato mosaic virus (ToMV). Tm-1 was introgressed from a wild tomato species, Solanum habrochaites, and has been used to protect tomato plants from ToMV infection (Pelham 1966). Tm-1 inhibits the multiplication of ToMV within protoplasts (Motoyoshi and Oshima 1977), is overcome by ToMV mutants that have amino acid substitutions in the replication proteins (Meshi et al. 1988; Hamamoto et al. 1997), and does not elicit a hypersensitive reaction (Yamafuji et al. 1991). The gene still needed to be identified; however, positional cloning has been hampered by the extremely low frequency of recombination around the Tm-1 locus (Ohmori et al. 1996). In this study, I identified the Tm-1 gene product through a biochemical approach (Ishibashi et al. 2007). I also found that a recessive, ToMV-susceptible allele of Tm-1 encoded a functional inhibitor of RNA replication of other tobamoviruses, Tobacco mild green mosaic virus (TMGMV) and Pepper mild mottle virus (PMMoV), which cannot infect tomato (Ishibashi et al. 2009). Identification of the Tm-1 gene