Characterization of a ToMV isolate overcoming Tm-2² resistance gene in tomato

Tomato mosaic virus (ToMV) is easily transmitted in soil and by contact. By these reasons, it is relatively difficult to control ToMV disease in tomato. Incorporation of the Tm-2² gene has been widely used as a control method for ToMV, but ToMV isolates that overcome this resistance gene have been reported worldwide in recent years. In this study, we determined the entire nucleotide sequences of ToMV isolate [named ToMV-KMT (LC650928)], which was isolated from tomato plants showing symptoms of systemic necrosis in Kumamoto prefecture, Japan. We also analyzed the viral gene of ToMV-KMT that overcome the Tm-2² gene by constructing its infectious cDNA clone and by generating chimeric viruses with a non-breaking strain. According to previous research, Tm-2² recognizes the viral movement protein (MP) and exerts resistance by inducing hypersensitive reaction or hypersensitive cell death. We discovered that a mutation in the 240th amino acid (aspartic acid to tyrosine) of the MP of ToMV-KMT, which may stabilize the protein's structure, is responsible for the ability of this isolate to overcome the resistance of Tm-2².