Serological relationships between pathogenesis-related leaf proteins from four Nicotiana species, Solanum tuberosum, and Chenopodium amaranticolor

Abstract

Leaves of Nicotiana tabacum L. cv. Xanthi-nc, Nicotiana clevelandii Gray, Nicotiana rustica L., and Chenopodium amaranticolor Coste & Reyn. were infected with the U1 strain of tobacco mosaic virus and leaves of Nicotiana sylvestris Speg. & Comes and Solanum tuberosum L. cv. Kennebec were infected with the U2 strain. After 10 days, pathogenesis-related (PR) proteins from intercellular fluid extracts were separated by nondenaturing polyacrylamide gel electrophoretic (PAGE) systems for acidic or basic proteins, sometimes followed by denaturating PAGE with lithium dodecyl sulfate. PR proteins were then transferred to nitrocellulose to determine serological relationships. Using an antiserum directed against native PR protein b4 from 'Xanthi-nc' tobacco, serologically reacting acidic PR proteins could be detected in all plant species. Except for potato, related basic PR proteins were also found in all species. Serological relationships were further studied between 'Xanthi-nc' tobacco and 'Kennebec' potato PR proteins separated in PAGE gels under native conditions. Potato basic PR proteins with Rfs of 0.83, 0.85, and 1.00 were serologically related to tobacco acidic PR proteins of the b4 group. Potato acidic PR proteins with Rfs of 0.56, 0.58, 0.61, and 0.64 were related to tobacco acidic PR proteins of the b4 group. Potato acidic PR proteins with Rfs of 0.18 and 0.21 reacted with an antiserum against tobacco PR protein b9. Three potato acidic peroxidases were also serologically related to tobacco peroxidases b6a and b7a. Analysis with denaturing PAGE systems gave results difficult to interpret because bovine carbonic anhydrase, for example, cross-reacted with an antiserum against tobacco PR protein b4. A similar relationship could not be detected in PAGE systems under native conditions.