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Basic leucine zipper (bZIP) transcription factors play crucial roles in various abiotic stress responses as well as anthocyanin accumulation. Anthocyanins are most abundant in colorful skin radish, which exhibit strong antioxidant activity that offers benefits for human health. Here, a total of 135 bZIP-encoding genes were identified from radish genome. Synteny analysis showed that 104 radish and 63 ArabidopsisbZIP genes were orthologous. Transcriptome analysis revealed that 10 RsbZIP genes exhibited high-expression levels in radish taproot (RPKM>10). Specifically, RsbZIP010 exhibited down-regulated expression under Cd, Cr and Pb stresses, whereas RsbZIP031 and RsbZIP059 showed significant down-regulation under heat and salt stresses, respectively. RT-qPCR analysis indicated that RsbZIP011 and RsbZIP102 were significantly up-regulated in the tissues of radish with high anthocyanin contents. Furthermore, the promoter sequences of 39 anthocyanin-related genes were found to contain G-box or ACE-box elements that could be recognized by bZIP family members. Taken together, several RsbZIPs might be served as critical regulators in radish taproot under Cd, Cr, Pb, heat and salt stresses. RsbZIP011 and RsbZIP102 were the potential participants in anthocyanin biosynthesis pathway of radish. These results facilitate further investigation on functional characterization of bZIP genes in response to abiotic stress and anthocyanin biosynthesis in radish. [ABSTRACT FROM AUTHOR]

Main conclusion Among 247 RsAP2/ERF identified, the majority of the 21 representatives were preferably expressed under drought and heat while suppressed under heavy metals, indicating their potential roles in abiotic stress responses and tolerance. APETALA2/Ethylene-Responsive factor (AP2/ERF) transcription factor (TF) is one of the largest gene families in plants that play a fundamental role in growth and development as well as biotic and/or abiotic stresses responses. Although AP2/ERFs have been extensively characterized in many plant species, little is known about this family in radish, which is an important root vegetable with various medicinal properties. The available genome provides valuable opportunity to identify and characterize the global information on AP2/ERF TFs in radish. In this study, a total of 247 ERF family genes were identified from the radish genome, and sequence alignment and phylogenetic analyses classified the AP2/ERF superfamily into five groups (AP2, ERF, DREB, RAV and soloist). Motif analysis showed that other than AP2/ERF domains, other conserved regions were selectively distributed among different clades in the phylogenetic tree. Chromosome location analysis showed that tandem duplication may result in the expansion of RsAP2/ERF gene family. The RT-qPCR analysis confirmed that a proportion of AP2/ERF genes were preferably expressed under drought and heat stresses, whereas they were suppressed under the ABA and heavy metal stresses. These results provided valuable information for further evolutionary and functional characterization of RsAP2/ERF genes, and contributed to genetic improvement of stress tolerances in radish and other root vegetable crops. • Totally 247 AP2-ERF genes were firstly genome-widely identified in radish. • The AP2/ERF superfamily could be classified into five groups. • Tandem duplications play critical role in the expansion of RsAP2/ERF genes. • A proportion of AP2/ERF genes were differentially expressed under abiotic stresses. [ABSTRACT FROM AUTHOR]