Abstract
The transcription factors, B-box (BBX), belong to a subfamily of the zinc finger family of proteins and exhibit multiple biological functions in plant growth, development, and abiotic stress response pathways. In this study, a total of 23 CaBBX members were identified using the pepper reference genome database. According to the gene structure, conserved domains, and the phylogenetic tree, 23 CaBBX genes were divided into four groups, wherein the analysis of the promoter region indicated the presence of cis-acting elements related to plant development, hormones, and stress response. Interspecies collinearity analysis showed that the CaBBXs had three duplicated gene pairs, and the highest gene density was found on chromosomes 2 and 7. Transcriptome RNA-seq data and quantitative polymerase chain reaction (qRT-PCR) analysis of pepper plants spanning the entire period showed that more than half of the CaBBX genes were widely expressed in diversity tissues of pepper. Co-expression network analysis indicated that the CaBBXs and the anthocyanin structural genes had a close co-expression relationship. Thus, it was reasonably speculated that the CaBBX genes may be involved in the regulation of anthocyanin biosynthesis. Overall, this study involved the genome-wide characterization of the CaBBX family and may serve as a solid foundation for further investigations on CaBBX genes involved in the anthocyanin synthesis mechanisms and development in pepper.
Highlights
Pepper (Capsicum), an important species of the Solanaceae family, has significant popularity and economic value
A total of 23 CaBBX genes were identified in the pepper Zunla-1 genome, 22 CaBBXs were present in the pepper CM334 genome
The WRKY transcription factors (Cheng et al, 2020), HD-ZIP gene family (Zhang et al, 2021), and MYB, one of the largest gene families, have all been characterized by genome-wide studies (Wang et al, 2020b)
Summary
Pepper (Capsicum), an important species of the Solanaceae family, has significant popularity and economic value. It is widely cultivated in almost all areas with arable land, owing to its high nutritional value and complex germplasm diversity (Qin et al, 2014). Anthocyanins, a flavonoid compound, is widely present in plants. They can impart color and attract pollinators and seed dispersers and protect them from ultraviolet radiation. The biosynthesis of anthocyanins is characterized by catalysis through an enzymatic cascade. Malonyl-CoA and coumarin-CoA are used as substrates to produce chalcone through the catalysis of chalcone synthase (CHS). Dihydroflavonol 4-reductase (DFR), UDP-glucose: flavonoid 3-glucosyltransferase (UFGT), and anthocyanin synthase (ANS) regulate the anthocyanin synthesis in different species.
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