Coordinated regulation of anthocyanin biosynthesis in Chinese  bayberry (Myrica rubra) fruit by a R2R3 MYB transcription  factor.
Chinese bayberry (Myrica rubra) is a fruit crop with cultivars producing fruit ranging from white (Shuijing, SJ) to red (Dongkui, DK) and dark red-purple (Biqi, BQ), as a result of different levels of anthocyanin accumulation. Genes encoding the anthocyanin biosynthesis enzymes chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase (F3H), flavonoid 3'-hydroxylase (F3'H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS) and UDPglucose: flavonoid 3-O-glucosyltransferase (UFGT), as well as MrMYB1, a R2R3 MYB transcription factor homologous to known activators of anthocyanin biosynthesis, were isolated from ripe fruit of BQ. Differences in mRNA abundance of MrF3H, MrF3'H, MrDFR1, MrANS and MrUFGT were highly correlated with differential accumulation of anthocyanins between cultivars, suggesting coordinated regulation by transcription factors. The transcript level of MrMYB1 was strongly associated with the anthocyanin content in ripe fruit of the three cultivars, as well as different anthocyanin containing tissues of BQ fruit. Fruit bagging strongly inhibited anthocyanin accumulation in fruit as well as the expression of all anthocyanin biosynthetic genes and MrMYB1. Overexpression of MrMYB1 stimulated both anthocyanin accumulation and activated an Arabidopsis-DFR promoter in tobacco (Nicotiana tabacum). MrMYB1d, an allele with a 1 bp deletion at nucleotide 30 of coding sequence, was observed in SJ and DK fruit, suggesting that a nonsense mutation of the MYB1 protein may be responsible for no or low expression of MYB1 in the white and red fruit. These results show that coordinated expression of multiple biosynthetic genes is involved in anthocyanin accumulation in Chinese bayberry fruit, and this is regulated by MrMYB1.
Niu
Shan-Shan
SS
Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Huajiachi Campus, 310029 Hangzhou, People's Republic of China.
Xu
Chang-Jie
CJ
Zhang
Wang-Shu
WS
Zhang
Bo
B
Li
Xian
X
Lin-Wang
Kui
K
Ferguson
Ian B
IB
Allan
Andrew C
AC
Chen
Kun-Song
KS
D000595:Amino Acid Sequence; D000872:Anthocyanins / Q000096:biosynthesis*; D018389:Codon, Nonsense / Q000235:genetics; D005638:Fruit / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D031641:Myrica / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D000872:Anthocyanins; D018389:Codon, Nonsense; D010940:Plant Proteins; D014157:Transcription Factors