PROTEINS IMMUNOLOGICALLY RELATED TO DEHYDRINS IN FUCOID ALGAE

Adult fucoid algae on Atlantic shores have well-characterized, species -specific tolerances to the varying levels of desiccation that occur-f rom the low to high intertidal zones; however, less is Known about emb ryonic tolerances and their mechanistic basis. We investigated this by 1) exposing embryos of Fucus evanescens C. Agardh, F. spiralis L., an d F. vesiculosus L. from the Maine shore to osmotic desiccation in, hy persaline seawater and 2) examining whether these embryos contain spec ies-specific dehydrins, proteins first identified in higher plants tha t are hypothesized to confer tolerance to dehydration. Embryonic survi val when cultured in hypersaline seawater >100 practical salinity unit s (psu) correlated with the position of these species in the intertida l zone (F. spiralis > F. vesiculosus > F. evanescens), but all 1-day-o ld embryos of these species tolerated treatment with 100 psu or lower seawater. Proteins (17-105 kDa) immunologically related to dehydrins w ere detected on western blots with dehydrin antibodies raised against a synthetic peptide representing the conserved motif of dehydrins in h igher plants. These proteins were constitutive and unstable when subje cted to prolonged (>15 min) temperatures above 55 degrees C, unlike mo st higher plant dehydrins, which are inducible and remain soluble at 7 5 degrees-100 degrees C. The presence of these proteins was species- a nd stage-specific. Sperm off. vesiculosus had a characteristic protein of 76 kDa, whereas eggs and embryos (6 h to 3 days old) had a 92-kDa protein. By 1 week of age, expression of the 92-kDa protein decreased, and the 35-kDa protein of adults was present. Embryos of A. nodosum L . and Pelvetia compressa J. Agardh DeToni contained an, 85-kDa protein rather than the 92-kDa protein of Fucus embryos (F. distichus L., F. evanescens, F. spiralis, and F. vesiculosus). The 92-kDa protein becam e more abundant in embryos exposed to hyperosmotic seawater at 50 psu (F. evanescens and F. vesiculosus) or 150 psu (F. spiralis); however, dehydrin-like proteins of some molecular masses decreased in abundance simultaneously. Further characterization of these proteins is require d to establish whether they protect embryos against intertidal desicca tion.