Heterologous expression of maize chloroplast protein synthesis elongation factor (EF-Tu) enhances Escherichia coli viability under heat stress

A heat-tolerant maize line, ZPBL 1304, synthesizes increased amounts of chloroplast protein synthesis elongation factor (EF-Tu) under heat stress conditions. Previous studies have suggested that maize EF-Tu may be involved in the development of heat tolerance [Planta 212 (2001) 359; J. Plant Physiol. 153 (1998) 497]. In this study, we tested the hypothesis that overexpression. of maize EF-Tu enhances the viability of Escherichia coli under heat stress. The,approach was to expose E. coli transformed with a maize EF-Tu expression vector (pTrcHis2A-Zmeftul) to 55 degreesC and assess viability at 37 degreesC. Western blots showed E. call overproduced recombinant EF-Tu protein, and the protein seemed to be in a highly soluble form. E. coli overexpressing maize EF-Tu showed increased viability after exposure to heat stress, demonstrating that the maize EF-Tu is involved in the development of heat tolerance. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.