Shedding some light on cold acclimation, cold adaptation, and phenotypic plasticity

Abstract

In the past, the role of light as an energy source was largely ignored in research focused on cold acclimation and freezing tolerance in plants. However, cold acclimation is an energy-requiring process. We summarize research illustrating that photoautrophs as diverse as cyanobacteria (Plectonema boryanum), green algae (Chlorella vulgaris, Dunaliella salina, Chlamydomonas raudensis), crop plants (Triticum aestivum L., Secale cereale L., Brassica napus L.), and conifers (Pinus banksiana) L.) tailor the structure and function of the photosynthetic apparatus to changes in temperature and irradiance to maintain cellular energy balance called photostasis. Modulation of either temperature or irradiance results in a similar imbalance in cellular energy that is sensed through changes in chloroplastic excitation pressure. Thus, concepts of photostasis and excitation pressure provide the context through which one can explain the congruence of phenotypic plasticity and photosynthetic performance associated with cold acclimation and photoacclimation. Photosynthetic organisms can sense changes in temperature and irradiance through modulation of the redox state of the photosynthetic electron transport chain, which, in turn, governs phenotype through the regulation of nuclear gene expression and chloroplast biogenesis. We suggest that elucidation of the molecular mechanism(s) by which excitation pressure regulates phenotypic plasticity and photosynthetic performance will be essential in addressing the challenge of maintaining or perhaps enhancing crop productivity under the suboptimal growth conditions predicted to occur as a consequence of climate change.