Map-based cloning and characterization of BoCCD4, a gene responsible for white/yellow petal color in B. oleracea

Fengqing Han,Limei Yang,Honghao Lv,Jianghua Song,Mu Zhuang,Yong Wang,Bin Zhang,Yangyong Zhang,Huilin Cui,Zhiyuan Fang,Zhansheng Li,Xiaoping Liu

doi:10.1186/s12864-019-5596-2

Abstract

BackgroundBrassica oleracea exhibits extensive phenotypic diversity. As an important trait, petal color varies among different B. oleracea cultivars, enabling the study of the genetic basis of this trait. In a previous study, the gene responsible for petal color in B. oleracea was mapped to a 503-kb region on chromosome 3, but the candidate gene has not yet been identified.ResultsIn the present study, we report that the candidate gene was further delineated to a 207-kb fragment. BoCCD4, a homolog of the Arabidopsis carotenoid cleavage dioxygenase 4 (CCD4) gene, was selected for evaluation as the candidate gene. Sequence analysis of the YL-1 inbred line revealed three insertions/deletions and 34 single-nucleotide polymorphisms in the coding region of BoCCD4. Functional complementation showed that BoCCD4 from the white-petal inbred line 11–192 can rescue the yellow-petal trait of YL-1. Expression analysis revealed that BoCCD4 is exclusively expressed in petal tissue of white-petal plants, and phylogenetic analysis indicated that CCD4 homologs may share evolutionarily conserved roles in carotenoid metabolism. These findings demonstrate that BoCCD4 is responsible for white/yellow petal color variation in B. oleracea.ConclusionsThis study demonstrated that function loss of BoCCD4, a homolog of Arabidopsis CCD4, is responsible for yellow petal color in B. oleracea.

Highlights

Fine mapping of the petal color gene cpc-1 In a previous study, the candidate gene for petal color was mapped to a 503-kb region on C03 [31]
BoCCD4 was preferentially expressed in petals of the white-petal line (Fig. 3). These results revealed that BoCCD4 is a tissue-specific gene that may cleave carotenoids in floral tissues, which is very different from its homolog in Arabidopsis
Overexpression of BoCCD4 in YL-1 results in a transition of petal color from yellow to white or pale yellow We introduced wild-type BoCCD4 driven by the CaMV35S promoter into the yellow-petal parent YL-1 using Agrobacterium-mediated B. oleracea transformation and obtained three independent overexpressing transgenic lines, OEX1, OEX2 and OEX3

Summary

Introduction

Petal color varies among different B. oleracea cultivars, enabling the study of the genetic basis of this trait. The flower is the reproductive structure of angiosperms, and petals exhibit extensive color variation, mainly due to the accumulation of flavonoids, carotenoids and/or betalain pigments. Flower can serve as a model for studying the relationship between phenotype and Carotenoids are mostly C40 isoprenoid compounds, comprising of over 750 members widely distributed in fungi, cyanobacteria, algae and plant [9]. Carotenoids biosynthesis takes place in plastids of plants. They present in photosynthetic tissues for light harvesting and photoprotection during photosynthesis [10]. The pathway of carotenoid biosynthesis has been well characterized, and most the enzymes involved in

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Discussion

Conclusion