Gene cloning and analysis of the pattern of expression of the transcription factor HymMYB2 related to blue flower formation in Hydrangea macrophylla

Flower color is one of the most important ornamental traits of flowering plants, and it has a major influence on the ornamental and economic value of flowers. The inflorescences of hydrangea are richly colored, and the plants with blue flowers are one of the most favorite types of hydrangeas. In this study, we identified the transcription factor HymMYB2 that is highly expressed in the sterile flowers of blue hydrangea cultivars. The open reading frame of the HymMYB2 was obtained by gene cloning, with a length of 939 bp that encodes 312 amino acids. HymMYB2 has R2 and R3 conserved domains, belongs to the R2R3-MYB family, and has the highest level of homology with the MYB2 of kiwifruit. The results of qPCR analysis showed that the HymMYB2 is expressed in all tissues and organs of hydrangea, and it is expressed at higher levels in blue tissues and organs. A correlation analysis showed that the level of expression of the HmMYB2 significantly correlated with the total anthocyanin content in the sterile flowers of the blue H.macrophylla 'Forever Summer' at the P < 0.01 level, but there was no correlation between the total anthocyanin content in sterile flowers of red and white hydrangea cultivars. The expression of HymMYB2 in the sterile flowers of blue H.macrophylla 'Forever Summer' correlated with the expression of C3 ' 5 ' H (flavonoid 3 ',5 '-hydroxylase), DFR (flavanone 4-reductase) and ANS (anthocyanidin synthase) at the P < 0.01 level and the expression of F3H (naringenin 3-dioxygenase) and BZ1 (anthocyanidin 3-o-glucosyltransferase) at the P < 0.05 level. The transcription factor HymMYB2 may regulate blue flower color formation by affecting the levels of C3 ' 5 ' H, DFR and ANS. In this study, we discovered that the transcription factor HymMYB2 has a positive regulatory effect on the formation of blue hydrangea flowers. The results provide a basis for the formation and breeding of blue hydrangea flowers.