title: Synthesis of very-long-chain fatty acids in the epidermis controls plant organ growth by restricting cell proliferation.
abstract: Plant organ growth is controlled by inter-cell-layer communication, which thus determines the overall size of the organism. The epidermal layer interfaces with the environment and participates in both driving and restricting growth via inter-cell-layer communication. However, it remains unknown whether the epidermis can send signals to internal tissue to limit cell proliferation in determinate growth. Very-long-chain fatty acids (VLCFAs) are synthesized in the epidermis and used in the formation of cuticular wax. Here we found that VLCFA synthesis in the epidermis is essential for proper development of Arabidopsis thaliana. Wild-type plants treated with a VLCFA synthesis inhibitor and pasticcino mutants with defects in VLCFA synthesis exhibited overproliferation of cells in the vasculature or in the rib zone of shoot apices. The decrease of VLCFA content increased the expression of IPT3, a key determinant of cytokinin biosynthesis in the vasculature, and, indeed, elevated cytokinin levels. These phenotypes were suppressed in ipt3;5;7 triple mutants, and also by vasculature-specific expression of cytokinin oxidase, which degrades active forms of cytokinin. Our results imply that VLCFA synthesis in the epidermis is required to suppress cytokinin biosynthesis in the vasculature, thus fine-tuning cell division activity in internal tissue, and therefore that shoot growth is controlled by the interaction between the surface (epidermis) and the axis (vasculature) of the plant body.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nobusawa
authors.forename: Yoko
authors.initials: Y
authors.lastname: Okushima
authors.forename: Noriko
authors.initials: N
authors.lastname: Nagata
authors.forename: Mikiko
authors.initials: M
authors.lastname: Kojima
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sakakibara
authors.forename: Masaaki
authors.initials: M
authors.lastname: Umeda
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D003583:Cytokinins / Q000096:biosynthesis; D005227:Fatty Acids / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D009154:Mutation; D009928:Organ Specificity; D010088:Oxidoreductases / Q000378:metabolism; D019441:Plant Epidermis / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000096:biosynthesis; D018520:Plant Shoots / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D058526:Plant Vascular Bundle / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D013450:Sulfones / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014230:Triazoles / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D005227:Fatty Acids; C477363:PEPINO protein, Arabidopsis; D010937:Plant Growth Regulators; D034741:RNA, Small Interfering; D013450:Sulfones; D014157:Transcription Factors; D014230:Triazoles; C444649:cafenstrole; D010088:Oxidoreductases; C019984:cytokinin oxidase; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase; C518664:CDKB2;1 protein, Arabidopsis; D018844:Cyclin-Dependent Kinases