The lack of a stress response in Hydra oligactis is due to reduced hsp70 mRNA stability

Abstract

Synthesis and degradation of hsp70 mRNA was examined and compared in Hydra species living in different habitats and showing different heat-shock response. Hydra oligactis is restricted to habitats of low temperature and relatively stable pH. We have shown previously that this species is unable to acquire thermotolerance [Bosch, T., Krylow, S., Bode, H. & Steele, R. (1988) Proc. Natl Acad. Sci. USA 85, 7927Ϫ7931] and synthesizes significantly less heat-shock protein and hsp70 mRNA [Gellner, K., Praetzel, G. & Bosch, T. C. G. (1992) Eur. J. Biochem. 210, 683Ϫ691] in response to stress than related species, such as Hydra vulgaris or Hydra magnipapillata, which are adapted to habitats of wide temperature range and variable water quality. To examine the mechanisms responsible for the differential heatshock responses in these species, a construct containing H. magnipapillata hsp70 regulatory sequences fused to firefly luciferase was introduced into H. oligactis and H. magnipapillata polyps, and expression of luciferase examined. The results showed that luciferase can be expressed equally well in a heatinducible manner in both species, suggesting that H. oligactis heat-shock factor can interact with H. magnipapillata heat-shock elements. Northern blots of A-amanitin-treated polyps demonstrated that the half-life of hsp70 mRNA in heat-shocked H. oligactis is drastically shorter than in H. magnipapillata. Thus, differences in hsp70 mRNA stability appear to be responsible for the habitat-correlated differences in the stress response in Hydra species.Keywords : heat shock; hydra; RNA stability.All cells respond to stress with the synthesis of a small group of highly conserved proteins, termed heat-shock proteins [1,2]. One of the most conserved and best characterized heat-shock proteins is the 70-kDa heat-shock protein (Hsp70). The level of Hsp70 synthesis is controlled transcriptionally and posttranscriptionally through repression of hsp70 mRNA synthesis and destabilization of hsp70 transcripts [3]. The role of heat-shock proteins in protein folding, translocation through membranes and acquisition of thermotolerance has been the subject of numerous studies [4]. Research on heat-shock proteins, however, has been largely confined to cultured cells in the laboratory. Very little is known about the ecological significance of such proteins for organisms of closely related species living under different environmental conditions [5,6].When studying the stress response in the freshwater polyp Hydra, we observed differences in different species [7Ϫ9]. In response to stress Hydra vulgaris (formerly called Hydra attenuata [10]) and Hydra magnipapillata induce synthesis of several heat-shock proteins. In contrast, Hydra oligactis is unable to induce synthesis of heat-shock proteins and to acquire thermotolerance. The difference in the stress response is correlated with differences in the natural habitats : while H. vulgaris and H. magnipapillata polyps live in a wide range of freshwater environments under variable temperatures, H....

Long-term maintenance of species-specific bacterial microbiota in the basal metazoan Hydra

“…1B) and Hydra vulgaris (Fig. 1C), are remarkably different in their stress response (7,8). These differences appear to be correlated with differences in the antimicrobial activity against different bacteria (T.C.G.B., unpublished data).…”

Hydra, a model system for environmental studies

“…Despite this, metals may be sequestered and expelled by Hydra following exposure, as has been observed with uranium accumulated in discharged nematocyst cells which are routinely discarded as new cells replace them (Hyne et al, 1992a). Hydra have some capacity to express heat shock proteins of 70 kDa family which can constitute a protection mechanism against heavy metals since there is a cross protection mechanism between thermo tolerance and metal tolerance (Brennecke et al, 1998). However, there were some reports on the inability of Hydra oligactis to acquire thermo tolerance due to the low levels of heat shock protein expression in this species (Gellner et al, 1992).…”

Stress protein (HSP70 family) expression in intertidal benthic organisms: the example of <i>Anthopleura elegantissima</i> (Cnidaria: Anthozoa)

“…Stress protein responses have been examined in other cnidarians (Bosch and Praetzel, 1991;Miller et al, 1992;Sharp et al, 1994Sharp et al, , 1997Black et al, 1995;Fang et al, 1997;Brennecke et al, 1998;Wiens et al, 2000), but, to our knowledge, direct measurements of HSP protein responses have not been performed on intact cnidarians in situ during natural stress cycles such as tidal fluctuations. All studies have involved laboratory acclimated organisms or organisms brought to the laboratory and sampled under artificial conditions.…”