Authors: JUN JIANG, LUSHEN TIAN, SHIXING GUO, QINGQING YU, DEZHI ZENG, YINGZE NIU
Abstract: C?????arotenoids are a class of pigment elements present in photosynthetic organisms. T??he transcripts of specific carotenoid biosynthetic genes are probably important for the formation of different colors of flower petals. Zeaxanthin epoxidase (ZEP) enzyme activity is important for the high content of carotenoids in petals. In the present study, the zeaxanthin epoxidase gene in Brassica napus L. (BnZEP) was cloned and bioinformatically analyzed. The expression levels of the BnZEP gene in different plant organs and petals of different colors were investigated and compared in B. Napus. The results showed that the full-length cDNA sequence of BnZEP was 2228 bp, containing an open reading frame of 2010 bp and encoding a putative protein of 669 amino acids, with a molecular weight of 73.8 kDa and an isoelectric point (pI) of 6.16. The full-length genomic DNA sequence of BnZEP was 3268 bp, containing 16 exons and 15 introns, the same as in Arabidopsis thaliana (AtZEP). The predicted amino acid sequence of BnZEP revealed a close phylogenetic relationship among the cruciferous species, including Arabidopsis thaliana. The expression levels of BnZEP were remarkably different in different organs and in petals of different colors. Obviously higher expression levels of BnZEP were found in flower petals than in leaves and buds. Yellow petals had markedly higher expression levels of BnZEP than white petals. The results showed that the expression level of BnZEP was positively correlated with yellow petal color in B. Napus L. However, the highest expression level of BnZEP was observed in the pale yellow flower petals of the F1 hybrid (HW243 × ZHONGYOU 821). This implied that the expression level of BnZEP was not completely related to the degree of yellow petal color in B. Napus L. Based on the roles of ZEP enzyme in the xanthophyll cycle, it was suggested that the yellow flower color in Brassica napus L. Was probably associated with the accumulation of antheraxanthin and violaxanthin in the petals. However, further studies are necessary to identify the specific key carotenoid(s) for the yellow color in the petals of Brassica napus L.
Keywords: B????r????assica napus L., flower color, ge??ne cloning, real-time quantitative PCR, zeaxanthin epoxidase
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