A cold change: how short low temperature exposure affects primary metabolism in leaves and stems of two eucalyptus species

Plants often modify their metabolism in order to regain homeostasis and maintain survival in the face of stressful conditions. Here, two species of eucalyptus, E. globulus and E. grandis (adapted and non-adapted to low temperature, respectively), were exposed to either 10 °C or 25 °C over 24 h, and changes in gene expression and metabolite levels were analyzed. The aim of this experiment was to investigate the dynamic of short period changes in the energy metabolism of source (leaves) and sink (stem) tissues in these contrasting species regarding low temperature. We expected to observe a distinct pattern on carbon metabolism and source-to-sink relationship between both species which would be related to their different vegetative responses when facing low temperatures. In that way, E. globulus plants showed a differential expression in leaves and stems of SnRK1 genes system (responsible for energy availability control in plants), that was strongly associated to the changes in carbon metabolism and the main difference between the response when both species face cold. Taken together, the results suggest that low temperatures (10 °C) are able to increase the sink strength of stem tissues and the carbon assimilation in leaves of E. globulus, supporting a higher vegetative growth rate. In E. grandis, on the other hand, exposure to 10 °C promoted a higher consumption of carbon skeletons without better growth rate as a counterpart, suggesting that under cold conditions, these two eucalyptus species differ in the way they coordinate the interaction between the activation of SnRK1 system and primary metabolism in source and sink tissues.