The T omato spotted wilt virus cell‐to‐cell movement protein ( NS M ) triggers a hypersensitive response in S w‐5 ‐containing resistant tomato lines and in N icotiana benthamiana transformed with the functional S w‐5b resistance gene copy

Summary Although the S w‐5 gene cluster has been cloned, and S w‐5b has been identified as the functional gene copy that confers resistance to T omato spotted wilt virus ( TSWV ), its avirulence ( A vr ) determinant has not been identified to date. N icotiana tabacum ‘ SR1 ‘ plants transformed with a copy of the S w‐5b gene are immune without producing a clear visual response on challenge with TSWV , whereas it is shown here that N . benthamiana transformed with S w‐5b gives a rapid and conspicuous hypersensitive response ( HR ). Using these plants, from all structural and non‐structural TSWV proteins tested, the TSWV cell‐to‐cell movement protein ( NS M ) was confirmed as the A vr determinant using a Potato virus X ( PVX ) replicon or a non‐replicative pEAQ ‐ HT expression vector system. HR was induced in S w‐5b ‐transgenic N . benthamiana as well as in resistant near‐isogenic tomato lines after agroinfiltration with a functional cell‐to‐cell movement protein ( NS M ) from a resistance‐inducing ( RI ) TSWV strain ( BR ‐01), but not with NS M from a S w‐5 resistance‐breaking ( RB ) strain ( GRAU ). This is the first biological demonstration that S w‐5 ‐mediated resistance is triggered by the TSWV NS M cell‐to‐cell movement protein.