CmMYB#7, an R3 MYB transcription factor, acts as a negative regulator of anthocyanin biosynthesis in chrysanthemum

Abstract

‘Jimba’, a well-known white flowered chrysanthemum cultivar, occasionally and spontaneously produces red colored petals under natural cultivation, but there is little information about the molecular regulatory mechanism underlying this process. We analysed the expression patterns of 91 MYB transcription factors in ‘Jimba’ and ‘Turning red Jimba’ and identified an R3 MYB, CmMYB#7, whose expression was significantly decreased in ‘Turning red Jimba’ compared with ‘Jimba’, and confirmed it is a passive repressor of anthocyanin biosynthesis. CmMYB#7 competed with CmMYB6, which together with CmbHLH2 is an essential component of the anthocyanin activation complex, for interaction with CmbHLH2 through the bHLH binding site in the R3 MYB domain. This reduced binding of the CmMYB6–CmbHLH2 complex and inhibited its ability to activate CmDFR and CmUFGT promoters. Moreover, using transient expression assays we demonstrated that changes in the expression of CmMYB#7 accounted for alterations in anthocyanin content. Taken together, our findings illustrate that CmMYB#7 is a negative regulator of anthocyanin biosynthesis in chrysanthemum.

MYB44 competitively inhibits the formation of the MYB340-bHLH2-NAC56 complex to regulate anthocyanin biosynthesis in purple-fleshed sweet potato

“…For example, AtMYB75, AtMYB113 and AtMYB114 in Arabidopsis [11]; MdMYB10 and MdMYB110a in apple [12,13]; PyMYB10 and PyMYB114 in pear [14,15]; LcMYB5 in litchi [16]; PaMYB10 in apricot [17]; and FaMYB10 in strawberry [18] have been reported to be involved in anthocyanin biosynthesis as activators. In addition to MYB activators, R3-MYB and some R2R3-MYB repressors, including the chrysanthemum CmMYB#7 (an R3-MYB), strawberry FaMYB1 and FaMYB44.1, peach PpMYB18 and potato StMYB44 (R2R3-MYBs) ones, have also been identified as participating in the flavonoid biosynthetic pathway [19][20][21][22].…”

Functional MYB transcription factor gene HtMYB2 is associated with anthocyanin biosynthesis in Helianthus tuberosus L.

“…GbMYB2 encodes a R2R3 MYB transcription factor and regulates anthocyanin biosynthesis in leaves of G. bicolor, another member of the Asteraceae [34]. CmMYB6 from C. morifoium, also a member of the Asteraceae, could induce an approximately 34-fold increase in transcription of CmDFR, with the help of MrbHLH [35]. Most importantly, the overexpression of exogenous HtMYB2 in tobacco activated the expression of the endogenous structural genes related to anthocyanin biosynthesis, and increased the anthocyanin concentration in the tobacco leaves.…”

Article Functional MYB transcription factor gene HtMYB2 is associated with anthocyanin biosynthesis in Helianthus tuberosus L.

“…GbMYB2 encodes a R2R3 MYB transcription factor and regulates anthocyanin biosynthesis in leaves of G. bicolor, another member of the Asteraceae [34]. CmMYB6 from C. morifoium, also a member of the Asteraceae, could induce an approximately 34-fold increase in transcription of CmDFR, with the help of MrbHLH [35]. Most importantly, the overexpression of exogenous HtMYB2 in tobacco activated the expression of the endogenous structural genes related to anthocyanin biosynthesis, and increased the anthocyanin concentration in the tobacco leaves.…”