Overexpression of the Arabidopsis<i>CBF3</i>Transcriptional Activator Mimics Multiple Biochemical Changes Associated with Cold Acclimation

TLDR

CBF genes are rapidly induced by low temperature and encode transcriptional activators that regulate C‑repeat/DRE-containing genes, with constitutive expression of CBF1 or CBF3 inducing COR genes and boosting freezing tolerance in nonacclimated Arabidopsis. The study examined whether Arabidopsis CBF regulatory genes influence cold acclimation, the process by which plants enhance freezing tolerance when exposed to low temperatures. Overexpressing CBF3 in Arabidopsis increased freezing tolerance in cold‑acclimated plants and elevated proline, soluble sugars, and P5CS transcripts, indicating CBF3 coordinates multiple cold‑acclimation responses.

Abstract

Abstract We further investigated the role of the ArabidopsisCBF regulatory genes in cold acclimation, the process whereby certain plants increase in freezing tolerance upon exposure to low temperature. The CBF genes, which are rapidly induced in response to low temperature, encode transcriptional activators that control the expression of genes containing the C-repeat/dehydration responsive element DNA regulatory element in their promoters. Constitutive expression of either CBF1 orCBF3 (also known as DREB1b andDREB1a, respectively) in transgenic Arabidopsis plants has been shown to induce the expression of target COR(cold-regulated) genes and to enhance freezing tolerance in nonacclimated plants. Here we demonstrate that overexpression ofCBF3 in Arabidopsis also increases the freezing tolerance of cold-acclimated plants. Moreover, we show that it results in multiple biochemical changes associated with cold acclimation:CBF3-expressing plants had elevated levels of proline (Pro) and total soluble sugars, including sucrose, raffinose, glucose, and fructose. Plants overexpressing CBF3 also had elevated P5CS transcript levels suggesting that the increase in Pro levels resulted, at least in part, from increased expression of the key Pro biosynthetic enzyme Δ1-pyrroline-5-carboxylate synthase. These results lead us to propose that CBF3 integrates the activation of multiple components of the cold acclimation response.