Rubisco activase (RCA) constrains the photosynthetic potential of plants at high temperatures (heat stress). Endogenous levels of RCA could serve as an important determinant of plant productivity under heat-stress conditions. Thus, in this study, the possible relationship between expression levels of RCA and plant yield in 11 European cultivars of winter wheat following prolonged exposure to heat stress was investigated. In addition, the effect of a short-term heat stress on RCA expression in four genotypes of wheat, five genotypes of maize, and one genotype of Arabidopsis thaliana was examined. Immunoblots prepared from leaf protein extracts from control plants showed three RCA cross-reacting bands in wheat and two RCA cross-reacting bands in maize and Arabidopsis. The molecular mass of the observed bands was in the range between 40 kDa and 46 kDa. Heat stress affected RCA expression in a few genotypes of wheat and maize but not in Arabidopsis. In wheat, heat stress slightly modulated the relative amounts of RCA in some cultivars. In maize, heat stress did not seem to affect the existing RCA isoforms (40 kDa and 43 kDa) but induced the accumulation of a new putative RCA of 45–46 kDa. The new putative 45–46 kDa RCA was not seen in a genotype of maize (ZPL 389) that has been shown to display an exceptional sensitivity to heat stress. A significant, positive, linear correlation was found between the expression of wheat 45–46 kDa RCA and plant productivity under heat-stress conditions. Results support the hypothesis that endogenous levels of RCA could play an important role in plant productivity under supraoptimal temperature conditions.

EF-Tu proteins of plastids, mitochondria, and the cytosolic counterpart EF-1αin plants, as well as EF-Tu proteins of bacteria, are highly conserved and multifunctional. The functions of EF-Tu include transporting the aminoacyl-tRNA complex to the A site of the ribosome during protein biosynthesis; chaperone activity in protecting other proteins from aggregation caused by environmental stresses, facilitating renaturation of proteins when conditions return to normal; displaying a protein disulfide isomerase activity; participating in the degradation of N-terminally blocked proteins by the proteasome; eliciting innate immunity and triggering resistance to pathogenic bacteria in plants; participating in transcription when anE. colihost is infected with phages. EF-Tu genes are upregulated by abiotic stresses in plants, and EF-Tu plays important role in stress responses. Expression of a plant EF-Tu gene confers heat tolerance inE. coli, maize knock-out EF-Tu null mutants are heat susceptible, and over-expression of an EF-Tu gene improves heat tolerance in crop plants. This review paper summarizes the current knowledge of EF-Tu proteins in stress responses in plants and progress on application of EF-Tu for developing crop varieties tolerant to abiotic stresses, such as high temperatures.