College of Landscape Architecture, Zhejiang A&F University/Zhejiang Provincial Key Laboratory of Germplasm Innovation and Utilization for Garden Plants/Key Laboratory of National Forestry and Grassland Administration on Germplasm Innovation and Utilization for Southern Garden Plants, Hangzhou 311300, China
Abstract：Zinnia elegans is widely used in garden, flower border and other landscape greening, anthocyanin is one of the important pigments affecting flower coloration. basic helix-loop-helix (bHLH) transcription factors are the second largest family of transcription factors regulating anthocyanin synthesis. Among them, bHLH proteins related to flower color mainly belong to IIIf subgroup. At present, the regulation of anthocyanin synthesis by bHLH transcription factors in Z. elegans is unclear. In this study, the content of anthocyanins in the petals of 6 cultivars with different petal colors at different developmental stages of Z. elegans 'Dreamland' series was determined. Results showed that the content of anthocyanin in the petals of pink, rose, orange and red colors was the lowest at bud stage and the highest at half opening stage. The content of anthocyanins in the petals of red cultivar was the highest, followed by rose cultivar, while there was no anthocyanin in the petals of white and yellow cultivars. Based on the transcriptome data, 67 bHLH transcription factors were screened. Among them, ZeGL3 (Z. elegans glabra 3)(GenBank No. UXP87119.1) and ZeTT8 (Z. elegans transparent testa 8)(GenBank No. OP747298) belonged to the IIIf subgroup of bHLH family. Both ZeGL3 and ZeTT8 amino acid sequences contained conserved domains of MYB interaction region, bHLH and ACT. The expression level of ZeGL3 gene was the highest in petals, while the expression level of ZeTT8 gene was significantly higher in both petals and phyllaries. The expression of ZeGL3 gene in rose and red cultivar was generally higher than that in pink and coral cultivars (P<0.05). Through comprehensive analysis, it was considered that ZeGL3 gene was probably involved in the regulation of anthocyanin metabolism of Z. elegans. This study provides a theoretical basis for further revealing the molecular mechanism of IIIf subgroup gene of bHLH family regulating anthocyanin metabolism in Z. elegans.
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