Molecular ecology of the plant adaptation to high temperatures

Abstract

Plants respond to high temperature stress by activating a set of biochemical and physiological processes designed to hasten the thermo tolerance. The adaptation mechanisms include phenotypic, cellular and molecular modifications.The cellular responses involve alterations in amino acid metabolism, photosynthesis, carbohydrate metabolism, assimilation, and respiration. Cells accumulate solutes having protective function on the plasma membrane. Biochemical changes in lipid composition lead to increased membrane stability. The translational machinery becomes redirected towards preferential synthesis of stress-induced proteins, with concomitant cessation of synthesis of the steady-state proteins. With a few notable exceptions, most of the work related to molecular ecology of the heat stress response has concentrated on the rapid transcriptional activation of hsp genes and the ensuing production of heat shock proteins (HSPs). The high molecular weight HSPs are constitutively expressed at low levels. In contrast, the low molecular weights HSPs are produced de novo following stress. Advances have been accomplished in understanding the regulation of the hsp genes. Correlation between the production of heat shock proteins and increased thermo tolerance has been demonstrated in a few cases. The purpose of this review is to present recent information concerning the cellular and molecular mechanisms underlying plant acclimation to high temperature, and to address some of the responses underlying thermo tolerance.