Comparative Study of Plant Physiological Responses to Long-Term and Short-Term Daily Exposures to Low Temperature in the Presence of Protein-Synthesis Inhibitors

Abstract

The role of the protein synthesis system in the physiological responses to cold was assessed in chilling-sensitive (cucumber) and cold-tolerant (wheat) plants with the use of protein-synthesis inhibitors on 80S (cycloheximide, CHX) and 70S (chloramphenicol, CAP) ribosomes. The plants were subjected to a constant low temperature (LT treatment) at 12°C for cucumber and 4°C for wheat. Another regimen (DROP treatment) included a 2-h daily temperature drop to 12°C for cucumber and 4°C for wheat at the end of the night. Both inhibitors were found to suppress plant leaf growth under any temperature regimen, including the control (at a constant temperature of 23°C). They also reduced the rates of net photosynthesis, transpiration, dark respiration, and chlorophyll accumulation in all treatments but to a larger degree in the control and DROP-treated plants. The results confirmed the previously established dependence of enhanced cold tolerance on protein biosynthesis on 70S and, especially, 80S ribosomes in the LT-treated plants. It was demonstrated for the first time that the protein synthesis system is involved in the enhancement of plant cold tolerance afforded by short-term daily temperature drops. Temperature drops often occur under natural conditions and are used to reduce stem elongation in greenhouse production as an alternative to the use of retardants. The reported data are novel in that the enhanced cold tolerance of DROP-treated plants is accounted for not only by de novo protein synthesis but also by adaptive posttranslational control.