Comparative transcriptome-based identification and expression analysis of ATP-binding cassette (ABC) transporters reveals a likely role in the transport of <i>β</i>-caryophyllene and response to abiotic stress in <i>Brassica campestris</i>

Abstract

<italic>β</italic>-caryophyllene has physiological activities of antibacterial, antiedemic, anti-inflammatory, antitumor, and fungicidal activities. Previous research has focused on the synthesis of <italic>β</italic>-caryophyllene. However, little information is available about its involvement in <italic>β</italic>-caryophyllene transport. ATP-binding cassette (ABC) transporters are involved in the transport of multiple substrates such as amino acids, terpenes, and heavy metals. Herein, we present a genome-wide comparative transcriptome analysis between non-<italic>β</italic>-caryophyllene cultivars ('SZQ') and high <italic>β</italic>-caryophyllene cultivars ('XQC') to identify potential ABC functional gene activities that occur during plant development. This article analyzes potential ABC transporters that may transport <italic>β</italic>-caryophyllene by comparative transcriptome and GC-MS, and explores the genetic structure, evolutionary relationship, cis-acting element analysis, and transcription patterns of these transporters under different treatment conditions. Phylogenetic and cis-acting element analysis indicated that 8 genes in 'SZQ' and 'XQC' belonged to the ABCC, ABCG, and ABCE subfamilies and had the highest number of light-responsive elements and MYB binding sites. The RNA-seq and qRT-PCR results showed that 8 <italic>BcABC</italic> genes were expressed in a tissue- and development-specific manner, while their abundance apparently varied when plants were exposed to different treatment conditions. Pearson correlation analysis showed that ABCG18 is a potential carrier of <italic>β</italic>-caryophyllene, which might participate in substance transport in leaves and petioles. In summary, these observations opened up new future research directions for <italic>β</italic>-caryophyllene transport and provided insight into ABC family genes in <italic>Brassica campestris</italic>.