SEASONAL PATTERNS OF DEHYDRINS AND 70-KDA HEAT-SHOCK PROTEINS IN BARKTISSUES OF 8 SPECIES OF WOODY-PLANTS

Although considerable effort has been directed at identifying and unde rstanding the function and regulation of stress-induced proteins in he rbaceous plants, reports concerning woody plants are limited. Studies with herbaceous crops have revealed similarities in due types of prote ins that accumulate in response to a wide array of abiotic stresses an d hormonal cues such as the accumulation of abscisic acid. Many of the identified proteins appear to be related to dehydrins (the D-11 subgr oup of late-embryogenesis-abundant proteins). The objective of the pre sent study was to determine if seasonal induction of dehydrins is a co mmon feature In woody plants and to see if seasonal patterns existed f or other stress-induced proteins. Bark tissues from eight species of w oody plants were collected monthly for a period of 1.5 years. The spec ies included: peach (Prunus persica) cv. Loring; apple (Malus domestic a) cv. Golden Delicious; thornless blackberry (Rubus sp.) cv. Chester; hybrid poplar (Populus nigra); weeping willow (Salix babylonica); flo wering dogwood (Cornus florida); sassafras (Sassafras albidum); and bl ack locust (Robinia pseudo-acacia). Immunoblots of bark proteins were probed with a polyclonal antibody recognizing a conserved region of de hydrin proteins, and monoclonal antibodies directed against members of the HS70 family of heat-shock proteins. Some proteins, immunologicall y related to dehydrins, appeared to be constitutive; however, distinct seasonal patterns associated with winter acclimation were also observ ed in all species. The molecular masses of these proteins varied widel y, although similarities were observed in related species (willow and poplar). Identification of proteins using the monoclonal antibodies (H SP70, HSC70, BiP) was more definitive because of their inherent specif icity, but seasonal patterns were more variable among due eight specie s examined. This study represents only a precursory examination of sev eral proteins reported to be stress related in herbaceous plants, but the results indicate that these proteins are also common to woody plan ts and that further research to characterize their regulation and func tion in relation to stress adaptation and the perennial life cycle of woody plants is warranted.