Natural variation in flavonol and anthocyanin metabolism during cold acclimation in Arabidopsis thaliana accessions

In plants from temperate climates such as Arabidopsis thaliana, low, non-freezing temperatures lead to increased freezing tolerance in a process termed cold acclimation. During cold acclimation, massive changes in gene expression and in the content of primary metabolites and lipids have been observed. Here, we have analysed the influence of cold acclimation on flavonol and anthocyanin content and on the expression of genes related to flavonoid metabolism in 54 Arabidopsis accessions covering a wide range of freezing tolerance. Most flavonols and anthocyanins accumulated upon cold exposure, but the extent of accumulation varied strongly among the accessions. This was also true for most of the investigated transcripts. Correlation analyses revealed a high degree of coordination among metabolites and among transcripts, but only little correlation between metabolites and transcripts, indicating an important role of post-transcriptional regulation in flavonoid metabolism. Similarly, levels of many flavonoid biosynthesis genes were correlated with freezing tolerance after cold acclimation, but only the pool sizes of a few flavonols and anthocyanins. Collectively, our data provide evidence for an important role of flavonoid metabolism in Arabidopsis freezing tolerance and point to the importance of post-transcriptional mechanisms in the regulation of flavonoid metabolism in response to cold. It is well known that acclimation of plants to low temperatures elicits massive changes in gene expression and in the content of primary metabolites and lipids, but changes in secondary metabolites have not been characterized previously. We have analyzed the effect of cold on flavonol and anthocyanin content and on the expression of genes related to flavonoid metabolism in 54 Arabidopsis accessions covering a wide range of freezing tolerance. Most flavonols, anthocyanins and the related transcripts accumulated in the cold and for some, a correlation of pool sizes with freezing tolerance was found. There was little correlation between metabolite and transcript levels, indicating an important role of post-transcriptional regulation in flavonoid metabolism.