MdMYB9 and MdMYB11 are Involved in the Regulation of the JA-Induced Biosynthesis of Anthocyanin and Proanthocyanidin in Apples

Abstract

Anthocyanin and proanthocyanidin (PA) are important secondary metabolites and beneficial to human health. Their biosynthesis is induced by jasmonate (JA) treatment and regulated by MYB transcription factors (TFs). However, which and how MYB TFs regulate this process is largely unknown in apple. In this study, MdMYB9 and MdMYB11 which were induced by methyl jasmonate (MeJA) were functionally characterized. Overexpression of MdMYB9 or MdMYB11 promoted not only anthocyanin but also PA accumulation in apple calluses, and the accumulation was further enhanced by MeJA. Subsequently, yeast two-hybrid, pull-down and bimolecular fluorescence complementation assays showed that both MYB proteins interact with MdbHLH3. Moreover, Jasmonate ZIM-domain (MdJAZ) proteins interact with MdbHLH3. Furthermore, chromatin immunoprecipitation-quantitative PCR and yeast one-hybrid assays demonstrated that both MdMYB9 and MdMYB11 bind to the promoters of ANS, ANR and LAR, whereas MdbHLH3 is recruited to the promoters of MdMYB9 and MdMYB11 and regulates their transcription. In addition, transient expression assays indicated that overexpression of MdJAZ2 inhibits the recruitment of MdbHLH3 to the promoters of MdMYB9 and MdMYB11. Our findings provide new insight into the mechanism of how MeJA regulates anthocyanin and PA accumulation in apple.

Purple foliage coloration in tea (Camellia sinensis L.) arises from activation of the R2R3-MYB transcription factor CsAN1

“…Arabidopsis AtMYB75, Arabidopsis AtMYB90 and its homologous gene MdMYB1 in apple are crucial regulators of light-induced anthocyanin biosynthesis, and their degradation requires the CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) ubiquitin-dependent pathway in the dark4142. Similarly, several recent reports have described jasmonate-mediated anthocyanin accumulation through upstream control of MBW complex activity3943. However, these studies do not fully explain the underlying mechanism of up-regulation and down-regulation of anthocyanin regulators in specific environmental conditions.…”

Anthocyanin Biosynthesis in Apple Fruit

“…JAs mediate responses to wounding, and their capacity to stimulate pigmentation may be related to this role (Creelman and Mullet, 1997). An et al (2015) reported that the expression of the MYB TF genes MdMYB9 and MdMYB11 increased significantly compared to that of MdMYB1 in 'Orin' apple calli in response to JA treatment and in 'Gala' leaves in response to wounding. Subsequent functional analyses demonstrated that these two MYB TFs bound to the promoter regions of some flavonoid biosynthetic genes and induced anthocyanin accumulation in calli in the presence of JA.…”

Identification of Candidate Anthocyanin-Related Genes by Transcriptomic Analysis of ‘Furongli’ Plum (Prunus salicina Lindl.) during Fruit Ripening Using RNA-Seq

“…These regulators form an MBW complex that binds to promoters and activates transcription of structural genes of the anthocyanin biosynthetic pathway (Rahim et al, 2014; Li et al, 2016). The role of MBW in anthocyanin biosynthesis has been elucidated in fruit trees such as grape (Kobayashi et al, 2002, 2004; Walker et al, 2007), Chinese bayberry (Niu et al, 2010; Liu et al, 2013a,b), mangosteen (Palapol et al, 2009), blood orange (Crifò et al, 2011; Butelli et al, 2012), kiwifruit (Fraser et al, 2013), litchi (Lai et al, 2014, 2016), sweet cherry (Shen et al, 2014), apple (Takos et al, 2006; Espley et al, 2007; Xie et al, 2012; Chagné et al, 2013; An et al, 2015), and peach (Rahim et al, 2014; Zhou et al, 2014; Tuan et al, 2015). …”