PROTEIN EXPRESSION DURING HEAT STRESS IN THERMO-INTOLERANT AND THERMO-TOLERANT DIATOMS

• Published in: Journal of phycology Vol. 36; no. s3; p. 59
• Main Authors: Rousch, J. M., Bingham, S.E., Sommerfeld, M.R.
• Format: Journal Article
• Language: English
• Published: Boston, MA, USA Blackwell Science Inc 01.12.2000
• Subjects: Bacillariophyceae; Chaetoceros muelleri; Chrysophyta; Marine; Phaeodactylum tricornutum
• ISSN: 0022-3646; 1529-8817
• DOI: 10.1046/j.1529-8817.1999.00001-176.x

To better understand how diatoms are capable of responding to environmental stress, protein expression during heat treatment of a thermo‐intolerant (Phaeodactylum tricornutum) and thermo‐tolerant (Chaetoceros muelleri) diatom (Chrysophyta) was investigated. The stress response is a universal and conserved mechanism of cell survival to unfavorable conditions. Typically, a 10 to 15° C temperature elevation above cell growth optimal causes constitutively expressed proteins to decrease and heat shock proteins (HSPs) to increase. HSPs are categorized by molecular weight among five classes with each apparently specialized for a particular function that enhances cell survival. One‐dimensional SDS‐PAGE of diatoms subjected to heat treatment revealed that P. tricornutum exhibited a typical stress response, but C. muelleri did not exhibit a characteristic response even at a greatly elevated temperature (50° C). This result was confirmed by total soluble protein assays. Chaetoceros muelleri may contain higher basal levels of HSPs than P. tricornutum allowing C. muelleri to better tolerate elevated temperatures. Western blot analysis using pea HSP70 (70 kDa) antisera of heat‐treated P. tricornutum and C. muelleri validated the hypothesis that thermo‐tolerant cells contain higher levels of constitutively expressed HSPs. Two‐dimensional gel electrophoresis of heat‐treated cells indicate that the small HSPs (17–30 kDa) played a role in the stress response similar to that found in vascular plants. Ongoing work is focused on the manipulation of the stress response through over‐expression of key hsp genes.