Immunological identification of dehydrin-related proteins in the wood of five species of Populus and in Salix caprea L.

摘要

The winter and spring occurrence of dehydrin-related proteins (DRP) in the wood of deciduous trees was investigated. DRPs were immunologically detected in xylem extracts of five species of poplar (Populus balsamifera, P. X canadensis 'Robusta', P. deltoides, P. nigra var. italica, P. tremula) and in willow (Salix caprea) by Western blotting using a polyclonal antibody that was directed against a dehydrin protein in hybrid poplar. Xylem protein extracts obtained from dormant trees in winter stage offour other hardwood genera (Acer, Malus, Betula, and Fraxinus), were immunologically negative, supporting the specificity of the poplar dehydrin antibody. Two dehydrin-related proteins of similar molecular mass, between 116 and 120 kDa, could be identified in four poplar species. Two DRPs were also found, though of lower molecular masses, in P. tremula (87 and 92 kDa) and in Salix caprea (103 and 114 kDa). The difference in molecular masses of the DRP in poplars was not due to glycosylation. Evidence for multiple genes coding for DRPs of different molecular mass was obtained in Populus X canadensis 'Robusta' where a DRP of 120 kDa was present in one of the parents (P. nigra) while the second DRP of 118 kDa was found in the other (P. deltoides). The dehydrin-related proteins under investigation were heat stable to 80-85deg C, but not boiling resistant. Their involvement in acclimatization to low temperature of the xylem parenchyma cells was indicated by their seasonal appearance during winter, by their transient decrease during a warm period in winter, and by their disappearance within 2-3 weeks from twigs cut in winter and subjected to 21deg C. In contrast, the 32 kDa storage protein did not disappear.