ANTHOCYANIN1 of petunia controls pigment synthesis, vacuolar pH, and seed coat development by genetically distinct mechanisms.
ANTHOCYANIN1 (AN1) of petunia is a transcription factor of the basic helix-loop-helix (bHLH) family that is required for the synthesis of anthocyanin pigments. Here, we show that AN1 controls additional aspects of cell differentiation: the acidification of vacuoles in petal cells, and the size and morphology of cells in the seed coat epidermis. We identified an1 alleles, formerly known as ph6, that sustain anthocyanin synthesis but not vacuolar acidification and seed coat morphogenesis. These alleles express truncated proteins lacking the C-terminal half of AN1, including the bHLH domain, at an approximately 30-fold higher level than wild-type AN1. An allelic series in which one, two, or three amino acids were inserted into the bHLH domain indicated that this domain is required for both anthocyanin synthesis and vacuolar acidification. These findings show that AN1 controls more aspects of epidermal cell differentiation than previously thought through partially separable domains.
Spelt
Cornelis
C
Department of Developmental Genetics, Institute for Molecular Biological Sciences, Vrije Universiteit, de Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
Quattrocchio
Francesca
F
Mol
Joseph
J
Koes
Ronald
R
D000483:Alleles; D000595:Amino Acid Sequence; D000872:Anthocyanins / Q000096:biosynthesis* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins; D048429:Cell Size / Q000235:genetics; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018547:Plant Stems / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000254:growth & development*; D017386:Sequence Homology, Amino Acid; D019657:Solanaceae / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors; D014617:Vacuoles / Q000502:physiology*
D000872:Anthocyanins; D051792:Basic Helix-Loop-Helix Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C419702:anthocyanin1 protein, Petunia x hybrida