Patterns of protein synthesis in infected and stressed sugar beet ( Beta vulgaris L.)

Patterns of protein synthesis have been investigated in infected and stressed sugar beet roots and suspension cultured cells by two‐dimensional, iso‐electric focussing/sodium dodecyl sulphate polyacrylamide gel electrophoresis. Comparisons have been made between the protein complement of dormant field‐grown sugar beet roots and rhizomania‐infected roots originating from a UK outbreak, hydroponically grown, uninfected control and Polymyxa betae ‐infected sugar beet seedlings and control, biotic and abiotic elicitor‐treated sugar beet suspension cultured cells. Rhizomania‐infected roots and elicitor‐treated cells, but not roots, infected with P. betae alone showed large differences in the total protein complement. This result is consistent with the ability of P. betae to infect roots without inducing increased transcription of infection stress‐related genes and is clearly different from a large number of other biotrophic plant/fungus interactions in which a sub‐set of defence proteins are induced even in susceptible interactions in an attempted limitation of damage. Suppression of defence responses might be the mechanism by which P. betae is able to successfully colonise sugar beet. Beet plants with symptoms of rhizomania did not express polypeptides with mobilities characteristic of stress‐related products. However, polypeptides of mobilities characteristic of sub‐sets found within young roots were observed which is compatible with the typical symptoms of the disease.