title: Concerted transcription of auxin and carbohydrate homeostasis-related genes underlies improved adventitious rooting of microcuttings derived from far-red treated Eucalyptus globulus Labill mother plants.
abstract: Economically important plant species, such as Eucalyptus globulus, are often rooting recalcitrant. We have previously shown that far-red light enrichment applied to E. globulus donor-plants improved microcutting rooting competence and increased rooting zone/shoot carbohydrate ratio. To better understand this developmental response, the relative expression profiles of genes involved in auxin signaling (ARF6, ARF8, AGO1), biosynthesis (YUC3) and transport (AUX1, PIN1, PIN2); sucrose cleavage (SUS1, CWINV1), transport (SUC5), hexose phosphorylation (HXK1, FLN1) and starch biosynthesis (SS3) were quantified during adventitious rooting of E. globulus microcuttings derived from donor plants exposed to far-red or white light. Expression of auxin transport-related genes increased in the first days of root induction. Far-red enrichment of donor plants induced ARF6, ARF8 and AGO1 in microcuttings. The first two gene products could activate GH3 and other rooting related genes, whereas AGO1 deregulation of the repressor ARF17 may relief rooting inhibition. Increased sink strength at the basal stem with sucrose unloading in root tissue mediated by SUC and subsequent hydrolysis by SUS1 were also supported by gene expression profile. Fructose phosphorylation and starch biosynthesis could also contribute to proper carbon allocation at the site of rooting, as evidenced by increased expression of related genes. These data are in good agreement with increased contents of hexoses and starch at the cutting base severed from far-red exposed donor plants. To sum up, pathways integrating auxin and carbohydrate metabolism were activated in microcuttings derived from donor plants exposed to far red light enrichment, thereby improving rooting response in E. globulus.
authors.affiliation: Department of Botany, Federal University of Rio Grande do Sul, P.O. Box 15005, 91501-970 Porto Alegre, RS, Brazil.
authors.forename: Carolina Michels
authors.initials: CM
authors.lastname: Ruedell
authors.affiliation: Center for Biotechnology, Federal University of Rio Grande do Sul, P.O. Box 15005, 91501-970 Porto Alegre, RS, Brazil.
authors.forename: Márcia Rodrigues
authors.initials: MR
authors.lastname: de Almeida
authors.affiliation: Department of Botany, Federal University of Rio Grande do Sul, P.O. Box 15005, 91501-970 Porto Alegre, RS, Brazil; Center for Biotechnology, 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: D050260:Carbohydrate Metabolism; D005052:Eucalyptus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D006706:Homeostasis; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D018547:Plant Stems / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D015398:Signal Transduction
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins
keywords: Adventitious rooting; Auxin; Carbohydrates; Eucalyptus; Far-red light