title: Comparative transcriptional analysis provides new insights into the molecular basis of adventitious rooting recalcitrance in Eucalyptus.
abstract: Adventitious rooting (AR) is essential in clonal propagation. Eucalyptus globulus is relevant for the cellulose industry due to its low lignin content. However, several useful clones are recalcitrant to AR, often requiring exogenous auxin, adding cost to clonal garden operations. In contrast, E. grandis is an easy-to-root species widely used in clonal forestry. Aiming at contributing to the elucidation of recalcitrance causes in E. globulus, we conducted a comparative analysis with these two species differing in rooting competence, combining gene expression and anatomical techniques. Recalcitrance in E. globulus is reversed by exposure to exogenous indole-3-acetic acid (IAA), which promotes important gene expression modifications in both species. The endogenous content of IAA was significantly higher in E. grandis than in E. globulus. The cambium zone was identified as an active area during AR, concentrating the first cell divisions. Immunolocalization assay showed auxin accumulation in cambium cells, further indicating the importance of this region for rooting. We then performed a cambium zone-specific gene expression analysis during AR using laser microdissection. The results indicated that the auxin-related genes TOPLESS and IAA12/BODENLOS and the cytokinin-related gene ARR1may act as negative regulators of AR, possibly contributing to the hard-to-root phenotype of E. globulus.
authors.affiliation: Plant Physiology Laboratory, Center for Biotechnology and Department of Botany, Federal University of Rio Grande do Sul, P.O. Box 15005, 91501-970 Porto Alegre, RS, Brazil; Plant Gene Regulation and Bioinformatics Laboratory, Department of Plant Science, McGill University, Ste. Anne de Bellevue, QC H9X3V9, Canada.
authors.forename: Márcia Rodrigues
authors.initials: MR
authors.lastname: de Almeida
authors.affiliation: Plant Physiology Laboratory, Center for Biotechnology and Department of Botany, Federal University of Rio Grande do Sul, P.O. Box 15005, 91501-970 Porto Alegre, RS, Brazil.
authors.forename: Daniela
authors.initials: D
authors.lastname: de Bastiani
authors.affiliation: Plant Anatomy Laboratory, Department of Botany, Federal University of Rio Grande do Sul, 91501-970 Porto Alegre, RS, Brazil.
authors.forename: Marcos Letaif
authors.initials: ML
authors.lastname: Gaeta
authors.affiliation: Plant Anatomy Laboratory, Department of Botany, Federal University of Rio Grande do Sul, 91501-970 Porto Alegre, RS, Brazil.
authors.forename: Jorge Ernesto
authors.initials: JE
authors.lastname: de Araújo Mariath
authors.affiliation: Plant Physiology Laboratory, Center for Biotechnology and Department of Botany, Federal University of Rio Grande do Sul, P.O. Box 15005, 91501-970 Porto Alegre, RS, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: de Costa
authors.affiliation: Potato Research Centre, Agriculture and Agri-Food Canada, PO Box 20280, Fredericton, NB E3B 4Z7, Canada.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Retallick
authors.affiliation: Potato Research Centre, Agriculture and Agri-Food Canada, PO Box 20280, Fredericton, NB E3B 4Z7, Canada.
authors.forename: Lana
authors.initials: L
authors.lastname: Nolan
authors.affiliation: Potato Research Centre, Agriculture and Agri-Food Canada, PO Box 20280, Fredericton, NB E3B 4Z7, Canada.
authors.forename: Helen H
authors.initials: HH
authors.lastname: Tai
authors.affiliation: Plant Gene Regulation and Bioinformatics Laboratory, Department of Plant Science, McGill University, Ste. Anne de Bellevue, QC H9X3V9, Canada.
authors.forename: Martina V
authors.initials: MV
authors.lastname: Strömvik
authors.affiliation: Plant Physiology Laboratory, Center for Biotechnology and Department of Botany, Federal University of Rio Grande do Sul, P.O. Box 15005, 91501-970 Porto Alegre, RS, Brazil. Electronic address: fettneto@cbiot.ufrgs.br.
authors.forename: Arthur Germano
authors.initials: AG
authors.lastname: Fett-Neto
mesh_terms: D005052:Eucalyptus / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D061346:Laser Capture Microdissection; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; C030737:indoleacetic acid
keywords: Auxin; Gene expression; Laser capture microdissection; Rooting