Tomanek L, Somero G N
Hopkins Marine Station, Stanford University, Pacific Grove, California 93950-3094, USA.
Physiol Biochem Zool. 2000 Mar-Apr;73(2):249-56. doi: 10.1086/316740.
The time course and magnitude of the heat-shock response in relation to severity of thermal stress are important, yet poorly understood, aspects of thermotolerance. We examined patterns of protein synthesis in congeneric marine snails (genus Tegula) that occur at different heights along the subtidal to intertidal gradient after a thermal exposure (30 degrees C for 2.5 h, followed by 50 h recovery at 13 degrees C) that induced the heat-shock response. We monitored the kinetics and magnitudes of protein synthesis by quantifying incorporation of 35S-labeled methionine and cysteine into newly synthesized proteins and observed synthesis of putative heat-shock proteins (hsp's) of size classes 90, 77, 70, and 38 kDa. In the low- to mid-intertidal species, Tegula funebralis, whose body temperature frequently exceeds 30 degrees C during emersion, synthesis of hsp's commenced immediately after heat stress, reached maximal levels 1-3 h into recovery, and returned to prestress levels by 6 h, except for hsp90 (14 h). In contrast, in the low-intertidal to subtidal species, Tegula brunnea, for which 2.5 h at 30 degrees C represents a near lethal heat stress, synthesis of hsp's commenced 2-14 h after heat stress; reached maximal levels after 15-30 h, which exceeded magnitudes of synthesis in T. funebralis; and returned to prestress levels in the case of hsp90 (50 h) and hsp77 (30 h) but not in the case of hsp70 and hsp38. Exposures to 30 degrees C under aerial (emersion) and aquatic (immersion) conditions resulted in differences in hsp synthesis in T. brunnea but not in T. funebralis. The different time courses and magnitudes of hsp synthesis in these congeners suggest that the vertical limits of their distributions may be set in part by thermal stress.
热休克反应的时间进程和强度与热应激的严重程度相关，这是耐热性的重要方面，但人们对此了解甚少。我们研究了同属的海洋蜗牛（Tegula属）在热暴露（30℃持续2.5小时，随后在13℃恢复50小时）诱导热休克反应后，沿潮下带到潮间带梯度不同高度处蛋白质合成的模式。我们通过量化35S标记的甲硫氨酸和半胱氨酸掺入新合成蛋白质中的情况来监测蛋白质合成的动力学和强度，并观察到大小分别为90、77、70和38 kDa的假定热休克蛋白（hsp）的合成。在潮间带中低区域的物种Tegula funebralis中，其体温在暴露于空气中时经常超过30℃，热应激后hsp的合成立即开始，恢复1 - 3小时后达到最高水平，除了hsp90（14小时）外，6小时后恢复到应激前水平。相比之下，在潮间带低区域到潮下带的物种Tegula brunnea中，30℃持续2.5小时代表近乎致命的热应激，hsp的合成在热应激后2 - 14小时开始；15 - 30小时后达到最高水平，超过了T. funebralis中的合成强度；hsp90（50小时）和hsp77（30小时）恢复到应激前水平，但hsp70和hsp38没有。在空气中（暴露）和水中（浸没）条件下暴露于30℃导致T. brunnea中hsp合成存在差异，但T. funebralis中没有。这些同属物种中hsp合成的不同时间进程和强度表明，它们分布的垂直界限可能部分由热应激设定。
