Red Chinese Cabbage Transcriptome Analysis Reveals Structural Genes and Multiple Transcription Factors Regulating Reddish Purple Color.

Jana Jeevan Rameneni,Sushil Satish Chhapekar,Sonam Singh,Su Ryun Choi,Jhongchul Lee,Sang Heon Oh,Hyuna Kim,Man-Ho Oh,Man-Sun Kim,Oh Ha Kwon,Yong Pyo Lim,So Young Yi,Chang Yeol Lee,Sang Un Park,Sun-Ju Kim

doi:10.3390/ijms21082901

Abstract

Reddish purple Chinese cabbage (RPCC) is a popular variety of Brassica rapa (AA = 20). It is rich in anthocyanins, which have many health benefits. We detected novel anthocyanins including cyanidin 3-(feruloyl) diglucoside-5-(malonoyl) glucoside and pelargonidin 3-(caffeoyl) diglucoside-5-(malonoyl) glucoside in RPCC. Analyses of transcriptome data revealed 32,395 genes including 3345 differentially expressed genes (DEGs) between 3-week-old RPCC and green Chinese cabbage (GCC). The DEGs included 218 transcription factor (TF) genes and some functionally uncharacterized genes. Sixty DEGs identified from the transcriptome data were analyzed in 3-, 6- and 9-week old seedlings by RT-qPCR, and 35 of them had higher transcript levels in RPCC than in GCC. We detected cis-regulatory motifs of MYB, bHLH, WRKY, bZIP and AP2/ERF TFs in anthocyanin biosynthetic gene promoters. A network analysis revealed that MYB75, MYB90, and MYBL2 strongly interact with anthocyanin biosynthetic genes. Our results show that the late biosynthesis genes BrDFR, BrLDOX, BrUF3GT, BrUGT75c1-1, Br5MAT, BrAT-1, BrAT-2, BrTT19-1, and BrTT19-2 and the regulatory MYB genes BrMYB90, BrMYB75, and BrMYBL2-1 are highly expressed in RPCC, indicative of their important roles in anthocyanin biosynthesis, modification, and accumulation. Finally, we propose a model anthocyanin biosynthesis pathway that includes the unique anthocyanin pigments and genes specific to RPCC.

Highlights

Introgression breeding is an important traditional breeding technique for transferring key agronomic traits between two distinct species [1]
This result indicates that cyanidin 3-(feruloyl) diglucoside-5-(malonoyl) glucoside and pelargonidin 3-(caffeoyl) diglucoside-5-(malonoyl) glucoside are specific to this variety of Reddish purple Chinese cabbage (RPCC), and contribute to its color
Analyses of the transcriptome data from two varieties at the seedling stage revealed many unique transcripts including differentially expressed genes (DEGs) and transcription factor (TF) genes that are involved in a multitude of functions in growth and development

Summary

Introduction

Introgression breeding is an important traditional breeding technique for transferring key agronomic traits between two distinct species [1] Using this technique, improvements have been made to many Brassica traits, such as disease resistance, male sterility, seed color, oil quality traits, and other morphological traits [1,2]. Pekinensis L.) is reddish purple in color and rich in anthocyanins. Anthocyanins are a class of secondary metabolites that are synthesized through the phenylpropanoid pathway [5]. These water-soluble compounds with red, purple, or blue colors are synthesized in the cytosol and stored in the vacuole [6]. Anthocyanins play crucial roles in reducing damage from, and in defense responses against, abiotic stresses such as ultraviolet exposure, wounding, high light, chilling, pollution, osmotic stress, and nutrient deficiency, as well as biotic stresses such as pathogen infection [7]

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