title: FAMA is an essential component for the differentiation of two distinct cell types, myrosin cells and guard cells, in Arabidopsis.
abstract: Brassicales plants, including Arabidopsis thaliana, have an ingenious two-compartment defense system, which sequesters myrosinase from the substrate glucosinolate and produces a toxic compound when cells are damaged by herbivores. Myrosinase is stored in vacuoles of idioblast myrosin cells. The molecular mechanism that regulates myrosin cell development remains elusive. Here, we identify the basic helix-loop-helix transcription factor FAMA as an essential component for myrosin cell development along Arabidopsis leaf veins. FAMA is known as a regulator of stomatal development. We detected FAMA expression in myrosin cell precursors in leaf primordia in addition to stomatal lineage cells. FAMA deficiency caused defects in myrosin cell development and in the biosynthesis of myrosinases THIOGLUCOSIDE GLUCOHYDROLASE1 (TGG1) and TGG2. Conversely, ectopic FAMA expression conferred myrosin cell characteristics to hypocotyl and root cells, both of which normally lack myrosin cells. The FAMA interactors ICE1/SCREAM and its closest paralog SCREAM2/ICE2 were essential for myrosin cell development. DNA microarray analysis identified 32 candidate genes involved in myrosin cell development under the control of FAMA. This study provides a common regulatory pathway that determines two distinct cell types in leaves: epidermal guard cells and inner-tissue myrosin cells.
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shirakawa
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Haruko
authors.initials: H
authors.lastname: Ueda
authors.affiliation: Center for Ecological Research, Kyoto University, Otsu, Shiga 520-2113, Japan PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Atsushi J
authors.initials: AJ
authors.lastname: Nagano
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Tomoo
authors.initials: T
authors.lastname: Shimada
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kohchi
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan ihnishi@gr.bot.kyoto-u.ac.jp.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hara-Nishimura
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D018546:Hypocotyl / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D015151:Immunoblotting; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D054046:Plant Stomata / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D058526:Plant Vascular Bundle / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000201:enzymology
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D006026:Glycoside Hydrolases; D014157:Transcription Factors; C517481:FAMA protein, Arabidopsis; C510502:ICE1 protein, Arabidopsis; C538823:ICE2 protein, Arabidopsis; C511862:TGG1 protein, Arabidopsis; C511863:TGG2 protein, Arabidopsis; C022739:thioglucosidase