Genome-wide analysis of blueberry B-box family genes and identification of members activated by abiotic stress.

Background: B-box (BBX) proteins play important roles in regulating plant growth, development, and abiotic stress responses. BBX family genes have been identified and functionally characterized in many plant species, but little is known about the BBX family in blueberry (Vaccinium corymbosum).

Result: In this study, we identified 23 VcBBX genes from the Genome Database for Vaccinium (GDV). These VcBBXs can be divided into five clades based on gene structures and conserved domains in their encoded proteins. The prediction of cis-acting elements in the upstream sequences of VcBBX genes and protein-protein interactions indicated that VcBBX proteins are likely involved in phytohormone signaling pathways and abiotic stress responses. Analysis of transcriptome deep sequencing (RNA-seq) data showed that VcBBX genes exhibited organ-specific expression pattern and 11 VcBBX genes respond to ultraviolet B (UV-B) radiation. The co-expression analysis revealed that the encoded 11 VcBBX proteins act as bridges integrating UV-B and phytohormone signaling pathways in blueberry under UV-B radiation. Reverse-transcription quantitative PCR (RT-qPCR) analysis showed that most VcBBX genes respond to drought, salt, and cold stress. Among VcBBX proteins, VcBBX24 is highly expressed in all the organs, not only responds to abiotic stress, but it also interacts with proteins in UV-B and phytohormone signaling pathways, as revealed by computational analysis and co-expression analysis, and might be an important regulator integrating abiotic stress and phytohormone signaling networks.

Conclusions: Twenty-three VcBBX genes were identified in blueberry, in which, 11 VcBBX genes respond to UV-B radiation, and act as bridges integrating UV-B and phytohormone signaling pathways according to RNA-seq data. The expression patterns under abiotic stress suggested that the functional roles of most VcBBX genes respose to drought, salt, and cold stress. Our study provides a useful reference for functional analysis of VcBBX genes and for improving abiotic stress tolerance in blueberry.