DcMYB1 acts as a transcriptional activator of the carrot phenylalanine ammonia-lyase gene (DcPAL1) in response to elicitor treatment, UV-B irradiation and the dilution effect.
Expression of a carrot phenylalanine ammonia-lyase (PAL) gene (DcPAL1) in suspension-cultured carrot cells is induced by treatment with a fungal elicitor, ultraviolet B (UV-B) irradiation, and by transferring and diluting cells with fresh medium (the dilution effect). Box-L-like sequences are known as important cis-elements of genes for enzymes involved in the phenylpropanoid biosynthetic pathway. Six sequences, box-L0 to box-L5, exist in the DcPAL1 gene promoter region. In this study, we isolated cDNA encoding the R2R3 type of MYB transcription factor, DcMYB1, using yeast one-hybrid screening with box-L1 or box-L5 as target elements. DcMYB1 bound to boxes-L0, L1, L3/4, and L5 sequences (ACC(A/T)(A/T)CC) in vitro, and in yeast cells and carrot protoplasts. Transient expression of DcMYB1 could up-regulate DcPAL1 promoter activity in carrot protoplasts. Results of the transient expression experiment for the deletion-mutated promoters of boxes-L0, L1, L3, and L5 suggest that these box-L-like sequences were required for the complete activation of the DcPAL1 promoter by DcMYB1. Expression of DcMYB1 transcripts was induced 0.5 h after elicitor treatment or UV-B irradiation, and 2 h after the dilution effect. Induction of DcPAL1 expression occurred 1 h after DcMYB1 expression in all stress treatments, and repression of DcMYB1 expression by RNA interference caused cessation of the up-regulation of DcPAL1 expression in the elicitor treatment or with UV-B irradiation. These results suggest that DcMYB1 is the main regulatory factor acting on box-L sequences in the DcPAL1 gene that respond to environmental cues.
Maeda
Kazuhiro
K
Department of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, 184-8588 Koganei, Tokyo, Japan.
Kimura
Soichi
S
Demura
Taku
T
Takeda
Junko
J
Ozeki
Yoshihiro
Y
D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018552:Daucus carota / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000528:radiation effects; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant / Q000187:drug effects* / Q000528:radiation effects*; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D014466:Ultraviolet Rays
D018076:DNA, Complementary; D018744:DNA, Plant; D004268:DNA-Binding Proteins; D010937:Plant Growth Regulators; D015534:Trans-Activators; D010650:Phenylalanine Ammonia-Lyase