Cold-Induced Nuclear Import of CBF4 Regulates Freezing Tolerance

Abstract

C-repeat binding factors (CBFs) are crucial transcriptional activators in plant responses to low temperature. CBF4 differs in its slower, but more persistent regulation and its role in cold acclimation. Cold acclimation has accentuated relevance for tolerance to late spring frosts as they have become progressively more common, as a consequence of blurred seasonality in the context of global climate change. In the current study, we explore the functions of CBF4 from grapevine, VvCBF4. Overexpression of VvCBF4 fused to GFP in tobacco BY-2 cells confers cold tolerance. Furthermore, this protein shuttles from the cytoplasm to the nucleus in response to cold stress, associated with an accumulation of transcripts for other CBFs and the cold responsive gene, ERD10d. This response differs for chilling as compared to freezing and is regulated differently by upstream signalling involving oxidative burst, proteasome activity and jasmonate synthesis. The difference between chilling and freezing is also seen in the regulation of the CBF4 transcript in leaves from different grapevines differing in their cold tolerance. Therefore, we propose the quality of cold stress is transduced by different upstream signals regulating nuclear import and, thus, the transcriptional activation of grapevine CBF4.

Priming avocado with sodium hydrosulfide prior to frost conditions induces the expression of genes involved in protection and stress responses

“…More recently, CBF4 was also shown to regulate freezing tolerance in V. vinifera (Shi et al, 2022). Together, these propose that CBF4 has a key role in promoting improved tolerance to frost stress.…”

“…The connection of H 2 S to cold signalling, with respect to the ICE‐CBF‐COR pathway, has also been documented in Vitis vinifera , where exogenous H 2 S treatment resulted in enhanced expression of ICE1 and CBF3 (Fu et al, 2013). More recently, CBF4 was also shown to regulate freezing tolerance in V. vinifera (Shi et al, 2022). Together, these propose that CBF4 has a key role in promoting improved tolerance to frost stress.…”

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“…Among the Cold Box Factors, CBF4 differs by a slower but more persistent induction by cold stress (grapevine [ 87 , 88 ]; strawberry [ 89 ]; Arabidopsis thaliana [ 90 ]). Upon overexpression, it confers freezing tolerance (grapevine [ 91 ]; tobacco [ 92 ]; cotton [ 93 ]) and, thus, is thought to be a central activator of cold adaptation. Although other CBFs are always localised in the nucleus, CBF4 is found in the cytoplasm but is imported in response to cold stress [ 92 ].…”

“…Upon overexpression, it confers freezing tolerance (grapevine [ 91 ]; tobacco [ 92 ]; cotton [ 93 ]) and, thus, is thought to be a central activator of cold adaptation. Although other CBFs are always localised in the nucleus, CBF4 is found in the cytoplasm but is imported in response to cold stress [ 92 ]. The COR protein Xero2 (also known as Lti30) belongs to the acidic subclass of dehydrins, proteins that are induced in many plants in response to cold stress and are thought to act as cryoprotectants [ 94 ].…”