Arabidopsis R2R3-MYB transcription factor AtMYB60 functions as a transcriptional repressor of anthocyanin biosynthesis in lettuce (Lactuca sativa).
The MYB transcription factors play important roles in the regulation of many secondary metabolites at the transcriptional level. We evaluated the possible roles of the Arabidopsis R2R3-MYB transcription factors in flavonoid biosynthesis because they are induced by UV-B irradiation but their associated phenotypes are largely unexplored. We isolated their genes by RACE-PCR, and performed transgenic approach and metabolite analyses in lettuce (Lactuca sativa). We found that one member of this protein family, AtMYB60, inhibits anthocyanin biosynthesis in the lettuce plant. Wild-type lettuce normally accumulates anthocyanin, predominantly cyanidin and traces of delphinidin, and develops a red pigmentation. However, the production and accumulation of anthocyanin pigments in AtMYB60-overexpressing lettuce was inhibited. Using RT-PCR analysis, we also identified the complete absence or reduction of dihydroflavonol 4-reductase (DFR) transcripts in AtMYB60- overexpressing lettuce (AtMYB60-117 and AtMYB60-112 lines). The correlation between the overexpression of AtMYB60 and the inhibition of anthocyanin accumulation suggests that the transcription factorAtMYB60 controls anthocyanin biosynthesis in the lettuce leaf. Clarification of the roles of the AtMYB60 transcription factor will facilitate further studies and provide genetic tools to better understand the regulation in plants of the genes controlled by the MYB-type transcription factors. Furthermore, the characterization of AtMYB60 has implications for the development of new varieties of lettuce and other commercially important plants with metabolic engineering approaches.
Park
Jong-Sug
JS
Molecular Physiology and Biochemistry Division, National Institute of Agricultural Biotechnology, Suwon 441-707, South Korea. jongsug@rda.go.kr
Kim
Jung-Bong
JB
Cho
Kang-Jin
KJ
Cheon
Choong-Ill
CI
Sung
Mi-Kyung
MK
Choung
Myoung-Gun
MG
Roh
Kyung-Hee
KH
D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000595:Amino Acid Sequence; D000872:Anthocyanins / Q000096:biosynthesis*; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018545:Lactuca / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D000872:Anthocyanins; D029681:Arabidopsis Proteins; C504083:MYB60 protein, Arabidopsis; D014157:Transcription Factors; D000429:Alcohol Oxidoreductases; C056570:dihydroflavanol 4-reductase