Abstract
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 Arabidopsis bZIP 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.
Highlights
The basic leucine zipper family, as one of the largest and most diverse transcription factor (TF) families, is an important participator in various biological processes, such as seed maturation and germination, biotic or abiotic stress responses and hormone signaling [1,2]
To identify the candidate genes that may participate in abiotic stress response and anthocyanin biosynthesis in radish, the basic leucine zipper (bZIP) gene family members were systematically identified at the genome-wide level
Further SMART and InterPro analyses revealed that 135 genes could be assigned as radish bZIP genes, which were named RsbZIP001~RsbZIP135 (Table S1)
Summary
The basic leucine zipper (bZIP) family, as one of the largest and most diverse transcription factor (TF) families, is an important participator in various biological processes, such as seed maturation and germination, biotic or abiotic stress responses and hormone signaling [1,2]. HY5 has been found to play a vital role in anthocyanin biosynthesis in tomato and apple [13,15] These results provide useful information for comprehensive identification and characterization of bZIPs in root vegetable crops. Some bZIP TFs have been proven to be associated with different abiotic stress responses in many plant species, little information on the characterization of bZIP family is available in radish. To identify the candidate genes that may participate in abiotic stress response and anthocyanin biosynthesis in radish, the bZIP gene family members were systematically identified at the genome-wide level. Two potential bZIP genes related to anthocyanin biosynthesis were firstly identified in radish These results could provide valuable information on evolutionary relationship and functional divergence of the bZIP gene family in radish
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