Interactions between CmJAZ7 and CmMYB6/7 affect methyl jasmonate-induced anthocyanin accumulation in chrysanthemum ray florets

• Spraying treatment of 5 mmol/L MeJA solution promotes anthocyanin accumulation in flowers. • MeJA increases flower color and accumulation of anthocyanins and JAs through up-regulation of anthocyanin- and JA-related genes. • Interactions between CmJAZ7 and CmMYB6/7 affect MeJA-induced anthocyanin accumulation. In the post-harvest process of the chrysanthemums, the fading of the capitulum is severe because of the significant reduction of anthocyanin content at the later full-bloom stage, making the selection of appropriate post-harvest preservative essential for color retention and enhancement. Jasmonates (JAs) have positive significance in promoting the accumulation of plant pigments and the synthesis of secondary metabolites and delaying plant senescence, thus they are widely used as a new type of eco-friendly post-harvest preservative in many fruits. In the present study, the flower color of the chrysanthemum cultivar 'Riqie Taohong' deepened under the spraying treatment of methyl jasmonate (MeJA), accompanied by the increase of metabolite concentrations of anthocyanins and JAs as well as the expression of several genes involved in their biosynthetic and signaling pathway in the ray florets at the early capitulum developmental stage. The yeast two-hybrid and bimolecular fluorescence complementation assays showed that CmJAZ7 (jasmonate ZIM domain 7) strongly interacted with positive regulators CmMYB6/7 (v-myb avian myeloblastosis 6/7), which suppressed the activity of CmMYB6/7 and anthocyanin biosynthesis. Based on the above results, the molecular mechanism of exogenous MeJA application on the regulation of anthocyanin biosynthesis in chrysanthemum was supposed, which provided a reference for revealing the molecular mechanism of MeJA on the regulation of flower color in ornamental plants, as well as for enhancing the flower color of commercial flowers using harmless plant hormones at the post-harvest stage.