MYB12 and MYB22 play essential roles in proanthocyanidin and flavonol synthesis in red‐fleshed apple (Malus sieversii f. niedzwetzkyana)

Abstract

Flavonoids are major polyphenol compounds in plant secondary metabolism. Wild red-fleshed apples (Malus sieversii f. niedzwetzkyana) are an excellent resource because of their much high flavonoid content than cultivated apples. In this work, R6R6, R6R1 and R1R1 genotypes were identified in an F segregating population of M. sieversii f. niedzwetzkyana. Significant differences in flavonoid composition and content were detected among the three genotypes by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry analysis. Furthermore, two putative flavonoid-related genes encoding R2R3-MYB transcription factors, designated MYB12 and MYB22, were cloned and characterized. The expression patterns of MYB12 and MYB22 directly correlated with those of leucoanthocyanidin reductase and flavonol synthase, respectively. Their roles in flavonoid biosynthesis were identified by overexpression in apple callus and ectopic expression in Arabidopsis. MYB12 expression in the Arabidopsis TT2 mutant complemented its proanthocyanidin-deficient phenotype. Likewise, MYB22 expression in an Arabidopsis triple mutant complemented its flavonol-deficient phenotype. MYB12 could interact with bHLH3 and bHLH33 and played an essential role in proanthocyanidin synthesis. MYB22 was found to activate flavonol pathways by combining directly with the flavonol synthase promoter. Our findings provide a valuable perspective on flavonoid synthesis and provide a basis for breeding elite functional apples with a high flavonoid content.

The B‐box zinc finger protein MdBBX20 integrates anthocyanin accumulation in response to ultraviolet radiation and low temperature

“…However, MdTTG1 (WD40 class) neither interacts with MdMYB1 nor binds to the promoters of MdDFR and MdUFGT but may interact with MdbHLH3 and MdbHLH33 to regulate anthocyanin synthesis (An, Tian, Chen, Wang, & Hao, ). MdbHLH33 interacts with MdMYB16, which inhibits anthocyanin biosynthesis via the C ‐terminal EAR repressor, to weaken its inhibitory effect (Wang et al, ).…”

Solar UV light regulates flavonoid metabolism in apple (Malus x domestica)

“…Transcriptional regulation of flavonol synthesis was investigated in Arabidopsis initially (AtMYB12) (Mehrtens, Kranz, Bednarek, & Weisshaar, ; Stracke et al, ), with flavonol MYB regulating factors subsequently found in grape (VvMYBF1) (Czemmel et al, ). Recently, MdMYB22, the transcription factor involved in apple flavonol synthesis, has been identified as a homologue of AtMYB12 (Wang et al, ). This study shows that expression patterns of MYB22 correlate with FLS expression during apple fruit development and suggests that MYB22 activates the flavonol pathway by combining directly with the FLS promoter.…”

“…This study shows that expression patterns of MYB22 correlate with FLS expression during apple fruit development and suggests that MYB22 activates the flavonol pathway by combining directly with the FLS promoter. With key players in the genetic control of flavonol and anthocyanin synthesis found, the impact of light exposure on apple flavonoid biosynthesis has begun to receive more attention (Feng, Li, Ma, & Cheng, ; Peng et al, ; Vimolmangkang et al, ; Wang et al, ), yet there is a lack of understanding regarding the role of UV light as a key driver of flavonoid regulation in apple.…”

Solanum lycopersicum microRNA1916 targets multiple target genes and negatively regulates the immune response in tomato

“…Previous studies have also shown that UGT can affect the accumulation of anthocyanins whereas MYB12 plays an essential role in proanthocyanidin synthesis (Cheng et al, ; Wang, Xu, et al, ). Indeed, the levels of anthocyanins in the STTM1916 and Anti‐miR1916 transgenic plants were significantly higher than the level found in the control plants (Figure ).…”