Abstract
The basic leucine zipper (bZIP) proteins compose a family of transcription factors (TFs), which play a crucial role in plant growth, development, and abiotic and biotic stress responses. However, no comprehensive analysis of bZIP family has been reported in pepper (Capsicum annuum L.). In this study, we identified and characterized 60 bZIP TF-encoding genes from two pepper genomes. These genes were divided into 10 groups based on their phylogenetic relationships with bZIP genes from Arabidopsis. Six introns/exons structural patterns within the basic and hinge regions and the conserved motifs were identified among all the pepper bZIP proteins, on the basis of which, we classify them into different subfamilies. Based on the transcriptomic data of Zunla-1 genome, expression analyses of 59 pepper bZIP genes (not including CabZIP25 of CM334 genome), indicated that the pepper bZIP genes were differentially expressed in the pepper tissues and developmental stages, and many of the pepper bZIP genes might be involved in responses to various abiotic stresses and phytohormones. Further, gene expression analysis, using quantitative real-time PCR (qRT-PCR), showed that the CabZIP25 gene was expressed at relatively higher levels in vegetative tissues, and was strongly induced by abiotic stresses and phytohormones. In comparing with wild type Arabidopsis, germination rate, fresh weight, chlorophyll content, and root lengths increased in the CabZIP25-overexpressing Arabidopsis under salt stress. Additionally, CabZIP25-silenced pepper showed lower chlorophyll content than the control plants under salt stress. These results suggested that CabZIP25 improved salt tolerance in plants. Taken together, our results provide new opportunities for the functional characterization of bZIP TFs in pepper.
Highlights
Plant growth, development, and agricultural production are seriously limited by adverse environmental conditions such as drought, salinity, and extreme temperatures
All the CabZIP sequences came from the Zunla-1 genome except the CabZIP25, which was obtained from CM334 genome due to an incomplete basic leucine zipper (bZIP) domain in the Zunla1 genome
A genome-wide analysis of the CabZIP gene family was performed in pepper and a total of 60 CabZIPs were obtained from the two pepper genomes
Summary
Development, and agricultural production are seriously limited by adverse environmental conditions such as drought, salinity, and extreme temperatures. Unfavorable factors cause a series of damages to the plant morphology, physiology, and biochemistry and may significantly cause extensive losses to agricultural production and economic yield (Allakhverdiev et al, 2008). A number of defense mechanisms have been developed through resistance genes, encoding regulatory proteins such as protein kinases, phosphatases, and transcription factors (TFs). TFs are critical components of signaling regulatory networks in response to growth and environmental stresses through recognizing and binding to the specific cis-elements in the promoters of the target genes to regulate their expression. BZIP proteins play important roles in growth and development, besides responding to various biotic/abiotic stresses (Sornaraj et al, 2016)
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