Exploring the molecular mechanism of coloration differences in two Meconopsis wilsonii subspecies: australis and orientalis.

ABSTRACT

Flower color diversity is a key taxonomic trait in Meconopsis species, enhancing their appeal as ornamental flowers. However, knowledge of the molecular mechanisms of flower color formation in Meconopsis species is still limited. M. wilsonii subsp. australis (Australis) and M. wilsonii subsp. orientalis (Orientalis) have a developmental stage presenting red-purple flowers, while Orientalis also presents blue coloration at the full-bloom period, making them an important model for exploring the mechanism of blue flower formation in M. wilsonii. In this study, we collected petals from Australis and Orientalis at different developmental stages to compare the coloration differences between the two species and detect the molecular mechanisms of blue color in Orientalis. We identified that cyanidin was the main anthocyanin in the flowers of both species, and the blue color in Orientalis primarily arises from anthocyanins (Cyanidin-3-O-sambubioside). RNA sequencing analysis was performed to detect the gene expression in the anthocyanin biosynthesis pathway, and the results suggested that gene regulation for anthocyanin biosynthesis may not be the direct reason for blue color formation in Orientalis. In addition, the growth solid of Orientalis was rich in Fe and Mg ions, and a large amount of Fe and Mg ions accumulated in the petals of Orientalis. Combined with the gene functional enrichment results, we found that the purple and red-purple colors of these two species were presented by different glycosylation levels of cyanidin, while the violet color of Orientalis might be the results of metalloanthocyanins by Fe and Mg ions, which also relieved the toxicity caused by the high content of Fe and Mg ions in its cells. The environmental adaptation-related genes were highly expressed of in both species, such as adaptation to desiccation, water deprivation, freezing, etc. Our results revealed the coloration differences between Australis and Orientalis and described the molecular mechanisms of blue coloration in Orientalis. The data in our analysis could enrich the genetic resources for M. wilsonii for further studies.