title: Cuticular lipid composition, surface structure, and gene expression in Arabidopsis stem epidermis.
abstract: All vascular plants are protected from the environment by a cuticle, a lipophilic layer synthesized by epidermal cells and composed of a cutin polymer matrix and waxes. The mechanism by which epidermal cells accumulate and assemble cuticle components in rapidly expanding organs is largely unknown. We have begun to address this question by analyzing the lipid compositional variance, the surface micromorphology, and the transcriptome of epidermal cells in elongating Arabidopsis (Arabidopsis thaliana) stems. The rate of cell elongation is maximal near the apical meristem and decreases steeply toward the middle of the stem, where it is 10 times slower. During and after this elongation, the cuticular wax load and composition remain remarkably constant (32 microg/cm2), indicating that the biosynthetic flux into waxes is closely matched to surface area expansion. By contrast, the load of polyester monomers per unit surface area decreases more than 2-fold from the upper (8 microg/cm2) to the lower (3 microg/cm2) portion of the stem, although the compositional variance is minor. To aid identification of proteins involved in the biosynthesis of waxes and cutin, we have isolated epidermal peels from Arabidopsis stems and determined transcript profiles in both rapidly expanding and nonexpanding cells. This transcriptome analysis was validated by the correct classification of known epidermis-specific genes. The 15% transcripts preferentially expressed in the epidermis were enriched in genes encoding proteins predicted to be membrane associated and involved in lipid metabolism. An analysis of the lipid-related subset is presented.
authors.affiliation: Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Mi Chung
authors.initials: MC
authors.lastname: Suh
authors.forename: A Lacey
authors.initials: AL
authors.lastname: Samuels
authors.forename: Reinhard
authors.initials: R
authors.lastname: Jetter
authors.forename: Ljerka
authors.initials: L
authors.lastname: Kunst
authors.forename: Mike
authors.initials: M
authors.lastname: Pollard
authors.forename: John
authors.initials: J
authors.lastname: Ohlrogge
authors.forename: Fred
authors.initials: F
authors.lastname: Beisson
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D017343:Genes, Plant; D050356:Lipid Metabolism; D008563:Membrane Lipids / Q000096:biosynthesis / Q000235:genetics; D008855:Microscopy, Electron, Scanning; D020411:Oligonucleotide Array Sequence Analysis; D018547:Plant Stems / Q000254:growth & development / Q000378:metabolism; D011091:Polyesters / Q000378:metabolism; D015854:Up-Regulation; D014885:Waxes / Q000378:metabolism
chemical_list: D008563:Membrane Lipids; D011091:Polyesters; D014885:Waxes; C000521:cutin