An Osmotic Stress Protein of Cyanobacteria Is Immunologically Related to Plant Dehydrins

Abstract

Dehydrins are a family of desiccation proteins that were identified originally in plants (T.J. Close, A.A. Kortt, P.M. Chandler [1989] Plant Mo1 Biol 13: 95-108; G. Calau, T.J. Close 119921 Plant Physiol 98: 1523-1525. Dehydrins are characterized by the consensus amino acid sequence domain EKKCIMDKIKEKLPG found at or near the carboxy terminus; the core of this domain (KIKEKLPC) may be repeated from one to many times within the complete polypeptide. Dehydrins generally accumulate in plants in response to dehydration stress, regardless of whether the stimulus is evaporation, chilling, or a decrease in externa1 osmotic potential. Polyclonal antibodies highly specific to the consensus carboxy terminus of plant dehydrins were used to search for dehydrins in cyanobacteria, many of which are known to survive desiccation. A 40-kD osmoticstress-induced protein was identified in Anabaena sp. strain PCC 7120. The 40-kD protein was usually not detected in logarithmic cultures and was induced by shifting the growth medium to higher solute concentrations. Severa1 solutes have inductive effects, including sucrose, sorbitol, and polyethylene glycol (PEG). Measurements of osmotic potential suggest that a shift of -0.5 MPa (sucrose and PEC) or -1.2 MPa (sorbitol) is sufficient to induce synthesis of the 40-kD protein. Glycerol, which is highly permeable, was not an inducer at -1.2 MPa (0.5 M), nor was the plant hormone abscisic acid. lnduction appears to be evoked by a shift in osmotic potential approximately equal in absolute magnitude to the expected turgor pressure of bacterial cells in logarithmic phase growth. A dehydrinlike polypeptide was also identified among osmotically induced proteins from two other filamentous, heterocyst-forming cyanobacteria. A 40-kD protein was observed in Calothrix sp. strain PCC 7601, and in Nostoc sp. strain Mac-R2, an osmotic-induced doublet at 39 and 40 kD was observed. From these data, it appears that cyanobacteria produce a dehydrin-like protein under osmotic stress. IThe responses of living organisms to abiotic stress show remarkable similarities over a wide evolutionary distance. This is particularly true of biochemical adaptations operating at the cellular level, as exemplified by the well-known heatshock response (Vierling, 1991; Zeilstra-Ryalls et al., 1991). Because drought or water stress is likely to have been as pervasive as heat shock during the evolution of life on this planet, we hypothesized that successful adaptive strategies for water-limited environments would be as conserved as the heat-shock response. Such conservation would be detectable in the primary structure of proteins functioning in waterstress adaptation. We report here on the presence of osmoregulated proteins in cyanobacteria that are immunologically related to a family of higher plant desiccation proteins known as dehydrins.Dehydrins are a family of proteins characterized by the amino acid consensus sequence KIKEKLPG, which is found one to many times within the complete dehydrin protein sequence (Galau and C...

Promoter and expression studies on an Arabidopsis thaliana dehydrin gene

“…[5]) as well as cyanobacteria [7]. A number of genes coding for these proteins have been identified in Arabidopsis thaliana [8][9][10][11][12][13].…”

Abscisic acid in lichens: variation, water relations and metabolism

“…Bartels et al, 1990). Preliminary experiments with lichens with an antibody against a dehydrin from maize seedlings (Close & Lammers, 1993) brought no evidence for a similar role of ABA for these organisms, but further investigations are needed. Smith, Hobson & Ellis (1987) raise the question of a possible involvement of ABA in regulating the symbiosis, Hartung & Gimmler (1994) propose a stress physiological role in respect to desiccation tolerance.…”

“…botanik.uni-wuerzburg.de synthesized ABA is readily released to its environment because of the high permeability of the fungal plasma membrane for ABA, Hartung & Gimmler (1994) suggested that ABA could be involved in stress resistance of lichens. They argued that ABA could be released from the mycobiont to the photobiont where desiccation related proteins could be formed (Close & Lammers, 1993).…”

Abscisic Acid-Induced Heat Tolerance in Bromus inermis Leyss Cell-Suspension Cultures (Heat-Stable, Abscisic Acid-Responsive Polypeptides in Combination with Sucrose Confer Enhanced Thermostability)

“…Dehydrin-like proteins also accumulate in osmotically stressed cyanobacteria (Close and Lammers, 1993), indicating that they have been evolutionarily conserved. A nove1 property of some ABAresponsive proteins (Jacobsen and Shaw, 1989) and dehydrins (Close et al, 1989) is their heat stability, or their resistance to heat-induced coagulation.…”