Acclimation of metabolism to light in Arabidopsis thaliana - the glucose-6-phosphate/phosphate translocator GPT2 directs metabolic acclimation

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Abstract

Mature leaves of plants transferred from low to high light typically increase their photosynthetic capacity. In Arabidopsis thaliana, this dynamic acclimation requires expression of GPT2, a glucose 6-phosphate/phosphate translocator. Here, we examine the impact of GPT2 on leaf metabolism and photosynthesis. Plants of wild-type and of a GPT2 knockout (gpt2.2) grown under low light achieved the same photosynthetic rate, despite having different metabolic and transcriptomic strategies. Immediately upon transfer to high light, gpt2.2 plants showed a higher rate of photosynthesis than wild-type (35%) however, over subsequent days, wild-type plants acclimated photosynthetic capacity, increasing photosynthesis 100 after 7 days. Wild-type plants accumulated more starch than gpt2.2 plants throughout acclimation. We suggest that GPT2 activity results in the net import of glucose 6-phosphate from cytosol to chloroplast, increasing starch synthesis. There was clear acclimation of metabolism, with short terms changes typically being reversed as plants acclimated. Distinct responses to light were seen in wild-type and gpt2.2 leaves. Significantly higher levels of sugar-phosphates were seen in gpt2.2. We suggest that GPT2 alters the distribution of metabolites between compartments and that this plays an essential role in allowing the cell to interpret environmental signals.

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Acclimation Arabidopsis thaliana glucose 6–phosphate GPT2 high light

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