Journal Article

A High Temperature-Sensitive Mutant of <i>Synechococcus</i> sp. PCC 7002 with Modifications in the Endogenous Plasmid, pAQ1

Aiko Kimura, Tomoko Hamada, Eugene H. Morita and Hidenori Hayashi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 2, pages 217-223
Published in print February 2002 | ISSN: 0032-0781
Published online February 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf022
A High Temperature-Sensitive Mutant of Synechococcus sp. PCC 7002 with Modifications in the Endogenous Plasmid, pAQ1

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  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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To study thermal adaptations in the cyanobacterium, Synechococcus sp. PCC 7002, we screened about 3,000 mutants for their tolerance to high temperature, and found one, SHT1, that is sensitive to high-temperature stress. The mutant had a modified gene construct in the endogenous plasmid, pAQ1. One of the four ORFs, ORF93, was duplicated, and its mRNA level was higher than in the wild type. At 38°C, the growth of SHT1 was retarded as compared with the wild type, and above 38°C, almost all the cells of SHT1 died. This temperature is much lower than that required for induction of heat shock proteins. Interestingly, in both the wild type and SHT1, the thermal stability of oxygen-evolving machinery increased upon acclimation to high temperatures. These findings indicate that the lack of thermal tolerance in the SHT1 strain is likely independent of the adaptation of the PSII complex and heat shock responses, whereas there are essential contributions of genes in the endogenous plasmid to the adaptation to high temperature. Thus, understanding the role of pAQ1 in the adaptation of Synechococcus sp. PCC 7002 to high-temperature environments is the first step in elucidating the function of this plasmid.

Keywords: Key words: Cyanobacteria — High-temperature stress — Plasmid — Tagged mutant — Thermal tolerance.; Abbreviations: Hsp, heat shock protein; SHT, mutant sensitive to high temperature; nt, nucleotide.

Journal Article.  4435 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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