Genome-wide characterization of pepper DREB family members and biological function of CaDREB32 in response to salt and osmotic stresses

Abstract

Dehydration response element binding (DREB) transcription factors play multiple roles in plant growth, development and response to abiotic stress. However, their biological functions in response to salt and osmotic stress in vegetables of the Solanaceae family are largely unclear. Here, 49 CaDREB genes classified into six groups were identified in the pepper genome. They showed high conservation in gene structure, with four tandem and six segmental duplications occurred during gene expansion, and various stress and hormone response, light and development-related cis-acting elements identified in their promoters. Transcription analyses demonstrated that they were all constitutively expressed in different organs, and were upregulated by both salt and osmotic stresses. Heterologous expression of CaDREB32 in tobacco restrained the normal growth, but increased the resistance of transgenic plants to salt and osmotic stresses. Further physiochemical analyses revealed that constitutive expression of CaDREB32 increased superoxide dismutase and peroxidase activities, and proline, total soluble sugar and chlorophyll, but decreased malondialdehyde, H₂O₂, and O₂^.- contents, accompanied with up-regulated expression of stress-related genes, in the leaves of transgenic plants under salt and osmotic stress conditions. Our results will provide insight into the possible biological functions of DREB family members in pepper, and theoretical guidance for the potential application of this family to the genetic breeding of new pepper cultivars with enhanced abiotic stress resistance.