C-repeat Binding Factor
Introduction
The C-repeat Binding Factor (CBF) is a transcription factor that plays a critical role in the cold acclimation process of plants. It is part of the AP2/ERF transcription factor family, which is involved in various biological processes such as development, metabolism, and response to environmental stresses.
Structure
The CBF protein consists of an AP2/ERF domain, which is responsible for DNA binding, and a C-terminal activation domain. The AP2/ERF domain contains 58-59 amino acids and is highly conserved among different plant species. This domain recognizes and binds to the C-repeat (CRT)/dehydration-responsive element (DRE) in the promoter region of cold-responsive (COR) genes.
Function
CBF proteins are induced by low temperature and bind to the CRT/DRE in the promoter region of COR genes, activating their transcription. This leads to the synthesis of proteins that protect the plant from freezing damage. The CBF pathway is one of the main pathways for cold acclimation in plants, and it is conserved among various plant species, including Arabidopsis, wheat, and barley.
Regulation
The expression of CBF genes is regulated at multiple levels, including transcriptional, post-transcriptional, and post-translational. At the transcriptional level, the ICE1 (Inducer of CBF Expression 1) protein activates the expression of CBF genes in response to cold stress. Post-transcriptionally, microRNAs such as miR398 and miR408 have been shown to regulate CBF expression. At the post-translational level, CBF proteins are regulated by ubiquitination and sumoylation.
Role in Cold Tolerance
The CBF pathway is crucial for plant survival under freezing conditions. Overexpression of CBF genes has been shown to enhance cold tolerance in various plant species. Conversely, plants with reduced CBF expression are more susceptible to freezing damage. Therefore, manipulation of the CBF pathway is a potential strategy for improving crop resistance to cold stress.