MdCOP1 Ubiquitin E3 Ligases Interact with MdMYB1 to Regulate Light-Induced Anthocyanin Biosynthesis and Red Fruit Coloration in Apple    

Abstract

MdMYB1 is a crucial regulator of light-induced anthocyanin biosynthesis and fruit coloration in apple (Malus domestica). In this study, it was found that MdMYB1 protein accumulated in the light but degraded via a ubiquitin-dependent pathway in the dark. Subsequently, the MdCOP1-1 and MdCOP1-2 genes were isolated from apple fruit peel and were functionally characterized in the Arabidopsis (Arabidopsis thaliana) cop1-4 mutant. Yeast (Saccharomyces cerevisiae) two-hybrid, bimolecular fluorescence complementation, and coimmunoprecipitation assays showed that MdMYB1 interacts with the MdCOP1 proteins. Furthermore, in vitro and in vivo experiments indicated that MdCOP1s are necessary for the ubiquitination and degradation of MdMYB1 protein in the dark and are therefore involved in the light-controlled stability of the MdMYB1 protein. Finally, a viral vectorbased transformation approach demonstrated that MdCOP1s negatively regulate the peel coloration of apple fruits by modulating the degradation of the MdMYB1 protein. Our findings provide new insight into the mechanism by which light controls anthocyanin accumulation and red fruit coloration in apple and even other plant species.

Unraveling the Mechanism Underlying the Glycosylation and Methylation of Anthocyanins in Peach

“…Anthocyanin accumulation has a great impact on fruit quality, and many genes involved in the regulation of anthocyanin biosynthesis have been identified in fruit species such as grape (Kobayashi et al, 2004), apple (Malus domestica; Takos et al, 2006;Espley et al, 2007;Li et al, 2012), and pear (Pyrus communis ;Feng et al, 2010). However, few studies have been reported on characterization of the UFGT and AOMT gene families in fruit trees.…”

Transcriptome Analysis Identities Key Candidate Genes Mediating Purple Ovary Coloration in Asiatic Hybrid Lilies

“…Anthocyanin accumulation is enhanced by ultraviolet-B light in apple [23][24][25] and red Chinese sand pear (P. pyrifolia) [26]. Blue light induces anthocyanin accumulation and expression of associated genes in apple fruits [27], strawberry (Fragaria × ananassa) fruits [28] and Chinese bayberry fruits [29].…”

Proteolytic degradation of the flavonoid regulators, TRANSPARENT TESTA8 and TRANSPARENT TESTA GLABRA1, inArabidopsisis mediated by the ubiquitin/26Sproteasome system

“…However, recent studies on the regulation of flavonoid biosynthesis pathways suggest that posttranscriptional and posttranslational mechanisms also play significant roles in the regulation of metabolic pathways. [6][7][8][9][10] The UPS has been demonstrated to regulate the activities of key regulatory proteins, including GL3, EGL3, PAP1 and PAP2, in the Arabidopsis flavonoid pathway. 9, 10 Here we show that two additional TFs, TT8 and TTG1, in the pathway are also targeted for proteasomal degradation, suggesting that the activities of most, if not all, TFs in the ternary complex that regulate the flavonoid pathway in Arabidopsis are regulated by UPS.…”

“…The R2R3MYBs, PAP1 and PAP2in Arabidopsis, and MdMYB1 in apple, are degraded in the dark by the UPS suggesting that the lightmediated anthocyanin accumulation in Arabidopsis and apple skin is due, at least in part, to the stabilization of these factors in light. 7,9 We have recently shown that the bHLH factors, GL3…”

“…4,5 Recent studies suggest that, in addition to transcriptional control, the anthocyanin pathway is also regulated by posttranscriptional and posttranslational control mechanisms. [6][7][8][9][10] To maintain cellular homeostasis, cells control the transcriptional machinery either through the expression of negative regulators, small RNAs, or by selectively degrading the proteins involved in metabolic pathways. In Arabidopsis, the single repeat MYBs, CAPRICE (CPC) and MYBL2, act as negative regulators of the anthocyanin biosynthesis pathway.…”