Tyramine and tyrosine decarboxylase gene contributes to the formation of cyanic blotches in the petals of pansy (Viola × wittrockiana)

Tyrosine decarboxylase (TYDC) can catalyze tyrosine into tyramine. Several studies demonstrated its roles in the acidity, salidroside and defense response. Here we found that TYDC from Viola × wittrockiana Gam (VwTYDC) may contribute to the formation of cyaninc blotches in the petal. VwTYDC gene were cloned from Viola × wittrockiana and the cDNA full-length sequences were 1634 bp encoding 494 amino acids. Gene expression of VwTYDC in different tissues and developmental stages showed that they were significantly higher expressed in flowers than stems, leaves and roots. In addition, VwTYDC expression were higher in cyanic blotches than those observed in acyanic blotches of petal. Metabolites analysis showed the contents of tyramine in cyanic blotches were also higher than that in acyanic areas. Furthermore, in vitro assay revealed the absorption peak of anthocyanins had a red shift and an increase when fed tyramine. We speculated that tyramine might contribute to flower color expression of pansy as co-pigment. Our study demonstrated for the first time that the contents of tyramine led to flower blotches formation in cyanic blotches of the petals in plant flowers, and this may due to the higher expression of VwTYDC gene.