Abstract
Camellia japonica is a plant species with great ornamental and gardening values. A novel hybrid cultivar Chunjiang Hongxia (Camellia japonica cv. Chunjiang Hongxia, CH) possesses vivid red leaves from an early growth stage to a prolonged period and is, therefore, commercially valuable. The molecular mechanism underlying this red-leaf phenotype in C. japonica cv. CH is largely unknown. Here, we investigated the leaf coloration process, photosynthetic pigments contents, and different types of anthocyanin compounds in three growth stages of the hybrid cultivar CH and its parental cultivars. The gene co-expression network and differential expression analysis from the transcriptome data indicated that the changes of leaf color were strongly correlated to the anthocyanin metabolic processes in different leaf growth stages. Genes with expression patterns associated with leaf color changes were also discussed. Together, physiological and transcriptomic analyses uncovered the regulatory network of metabolism processes involved in the modulation of the ornamentally valuable red-leaf phenotype and provided the potential candidate genes for future molecular breeding of ornamental plants such as Camellia japonica.
Highlights
Belonging to the Theaceae family, Camellia japonica is one of the ornamentally and economically most valuable flowering plants all over the world
The ratio between the contents of cyanidin-3-glucoside and the sum of catechin and epicatechin was obviously higher in Chunjiang Hongxia (CH) than Black Magic (BM) at each stage, and dropped quickly with age in CH (Figure 3C), which was in line with the leaf color changes from red to green and turning to dark
The expression levels of ANS and UFGT were much lower in 10-day samples of BM and Black Opal (BO) compared with CH, and both dramatically decreased after 10 days post leaf-expansion in CH, demonstrating that these two genes were crucial positive regulators of anthocyanin abundance in leaves at early growth stage (Figure 7)
Summary
Belonging to the Theaceae family, Camellia japonica is one of the ornamentally and economically most valuable flowering plants all over the world. Different from some Camellia species used as tea plants, such as Camellia sinensis, C. japonica is grown as a type of ornamental shrub mainly for its leaves and flowers [1]. Flavonoids in the leaves of camellias plants, such as catechins and table catechins, exhibited dynamic amounts during different developmental and growth stages, which were correlated to the leaf color changes [11]. No evidence regarding the gene regulatory network of leaf color change in C. japonica has been shown, and the molecular bases of the red-leaf phenotype of C. japonica plants need to be clarified. Comparative transcriptome analysis further uncovered the network of regulatory signaling pathways and key genes involved in the red-leaf phenotype of Camellia japonica plants
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