From the archives: Cold acclimation by plastid translation, metabolic allocation, and plant defense, and functions of a BiP–calreticulin complex

May 2022: Cold acclimation by plastid translation

Cold stress is a severe environmental constraint to plant growth and development. Low temperatures trigger several physiological and structural changes in chloroplasts, including light avoidance-like movements (see Fig. 1), photoinhibition of PSII, and a consequent burst in reactive oxygen species production at the photosynthetic electron transport chain. These observations suggest that chloroplast homeostasis plays a central role in regulating responses to cold. Gao et al. showed that translational activity in chloroplasts mediates tobacco acclimation to low temperatures. While translation is severely compromised by cold shock in procaryotes (Weber and Marahiel 2003), the authors showed that cold stress triggered only a partial reduction in chloroplast translation initiation in plants. Moreover, low temperatures triggered transient changes in ribosome distribution on chloroplast reading frames, causing translation adjustments of nonessential photosynthetic subunits. Reverse genetics revealed that chloroplast translational regulation of the nonessential subunit of the cytochrome b6f complex, PetL, is required for cold tolerance. It is tempting to speculate whether translational adjustments evolved as an energy-efficient alternative to overcome inherent overall deacceleration of metabolic fluxes during low temperatures.