Genome-Wide Identification and Expression Analysis of the Walnut C-Repeat Binding Factor Gene Family under Low-Temperature Stress

Abstract

The walnut (Juglans regia) is a nut with a high nutritional value and has been recognized throughout the world as an economically important woody plant. However, the walnut is vulnerable to abiotic stresses, especially low-temperature freezes, which can severely impede their growth and development, resulting in substantial financial losses. The CBF (C-repeat binding factor) gene, a unique plant transcription factor classified within the AP2/ERF (ethylene response factor) family, plays a vital role in the process of plants coping with abiotic stress, particularly low temperatures. This study utilized bioinformatics techniques to identify eight JrCBF genes within the walnut genome, distributed across six chromosomes. The upstream promoter sequences of these genes are rich in cis-regulatory elements related to hormonal responses and non-biotic stresses. Transcriptome data and qRT-PCR analysis revealed that JrCBF1 and JrCBF2 were significantly upregulated under low temperatures. JrCBF1 and JrCBF2 also responded positively to high-temperature stress. Under drought stress, JrCBF5 and JrCBF8 had a significant difference in their expression relative to other genes. To gain further insights into their functionality, subcellular localization experiments were conducted on JrCBF1 and JrCBF2, confirming their nuclear localization. These results provide valuable insights into the specific functions of CBF gene in enhancing the resistance of walnut to abiotic stress.