Transcriptome and chemical analyses identify candidate genes associated with flower color shift in a natural mutant of <i>Chrysanthemum × morifolium</i>

Abstract

Flower color variation in <italic>Chrysanthemum</italic> <bold>×</bold> <italic>morifolium</italic> is an important horticultural trait. This study identifies a natural bud sprout mutant of chrysanthemum cultivar Hanluhong (HLH) which normally produces red flowers. In the mutant (<italic>hlh</italic>), the tip of the petals turned golden yellow and gradually turned yellow from tip to the base. After two years of consecutive propagation through cuttings, the mutant traits were stable. Here, the contents of carotenoids and anthocyanidins were determined by HPLC-MS/MS. Compared to HLH, the <italic>hlh</italic> displayed significantly higher contents of lutein. Then we comparatively analyzed the transcriptome of the ray florets tissues during three flower developmental stages. Higher number of stage specific DEGs were found in mutant cultivar as compared to wild type. About 200 DEGs were filtered related to the metabolism of flavonoids, carotenoids, terpenoids, and anthocyanins. Combined with weighted gene co-expression network analysis (WGCNA) and qRT-PCR verification, <italic>CHI</italic>, <italic>DFR</italic>, <italic>ANS</italic> and <italic>CCD4</italic> genes that involved in anthocyanins biosynthesis and carotenoids degradation were identified as candidate genes. Among the transcription factors, MYB, bHLH and WD40 members showed significant expression variations between the two cultivars. These results improve our understanding of flower color variation especially red and yellow color transition in chrysanthemum.