Arabidopsis TRANSPARENT TESTA GLABRA2 is directly regulated by R2R3 MYB transcription factors and is involved in regulation of GLABRA2 transcription in epidermal differentiation.
Arabidopsis thaliana TRANSPARENT TESTA GLABRA2 (TTG2) encodes a WRKY transcription factor and is expressed in young leaves, trichomes, seed coats, and root hairless cells. An examination of several trichome and root hair mutants indicates that MYB and bHLH genes regulate TTG2 expression. Two MYB binding sites in the TTG2 5' regulatory region act as cis regulatory elements and as direct targets of R2R3 MYB transcription factors such as WEREWOLF, GLABRA1, and TRANSPARENT TESTA2. Mutations in TTG2 cause phenotypic defects in trichome development and seed color pigmentation. Transgenic plants expressing a chimeric repressor version of the TTG2 protein (TTG2:SRDX) showed defects in trichome formation, anthocyanin accumulation, seed color pigmentation, and differentiation of root hairless cells. GLABRA2 (GL2) expression was markedly reduced in roots of ProTTG2:TTG2:SRDX transgenic plants, suggesting that TTG2 is involved in the regulation of GL2 expression, although GL2 expression in the ttg2 mutant was similar to that in the wild type. Our analysis suggests a new step in a regulatory cascade of epidermal differentiation, in which complexes containing R2R3 MYB and bHLH transcription factors regulate the expression of TTG2, which then regulates GL2 expression with complexes containing R2R3 MYB and bHLH in the differentiation of trichomes and root hairless cells.
Ishida
Tetsuya
T
Plant Science Center, RIKEN, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
Hattori
Sayoko
S
Sano
Ryosuke
R
Inoue
Kayoko
K
Shirano
Yumiko
Y
Hayashi
Hiroaki
H
Shibata
Daisuke
D
Sato
Shusei
S
Kato
Tomohiko
T
Tabata
Satoshi
S
Okada
Kiyotaka
K
Wada
Takuji
T
D017360:Arabidopsis / Q000166:cytology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames / Q000235:genetics; D010641:Phenotype; D019441:Plant Epidermis / Q000166:cytology* / Q000648:ultrastructure; D018517:Plant Roots / Q000166:cytology / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; C482738:BOTRYTIS SUSCEPTIBLE1 protein, Arabidopsis; C089991:GL2 protein, Arabidopsis; D018398:Homeodomain Proteins; D012097:Repressor Proteins; C525050:TTG2 protein, Arabidopsis; D014157:Transcription Factors