title: Microarray analysis revealed upregulation of nitrate reductase in juvenile cuttings of Eucalyptus grandis, which correlated with increased nitric oxide production and adventitious root formation.
abstract: The loss of rooting capability following the transition from the juvenile to the mature phase is a known phenomenon in woody plant development. Eucalyptus grandis was used here as a model system to study the differences in gene expression between juvenile and mature cuttings. RNA was prepared from the base of the two types of cuttings before root induction and hybridized to a DNA microarray of E. grandis. In juvenile cuttings, 363 transcripts were specifically upregulated, enriched in enzymes of oxidation/reduction processes. In mature cuttings, 245 transcripts were specifically upregulated, enriched in transcription factors involved in the regulation of secondary metabolites. A gene encoding for nitrate reductase (NIA), which is involved in nitric oxide (NO) production, was among the genes that were upregulated in juvenile cuttings. Concomitantly, a transient burst of NO was observed upon excision, which was higher in juvenile cuttings than in mature ones. Treatment with an NO donor improved rooting of both juvenile and mature cuttings. A single NIA gene was found in the newly released E. grandis genome sequence, the cDNA of which was isolated, overexpressed in Arabidopsis plants and shown to increase NO production in intact plants. Therefore, higher levels of NIA in E. grandis juvenile cuttings might lead to increased ability to produce NO and to form adventitious roots. Arabidopsis transgenic plants constantly expressing EgNIA did not exhibit a significantly higher lateral or adventitious root formation, suggesting that spatial and temporal rather than a constitutive increase in NO is favorable for root differentiation.
authors.affiliation: The Institute of Plant Sciences, Volcani Center, PO Box 6, Bet-Dagan 50250, Israel.
authors.forename: Mohamad
authors.initials: M
authors.lastname: Abu-Abied
authors.forename: David
authors.initials: D
authors.lastname: Szwerdszarf
authors.forename: Inna
authors.initials: I
authors.lastname: Mordehaev
authors.forename: Aviv
authors.initials: A
authors.lastname: Levy
authors.forename: Oksana Rogovoy
authors.initials: OR
authors.lastname: Stelmakh
authors.forename: Eduard
authors.initials: E
authors.lastname: Belausov
authors.forename: Yossi
authors.initials: Y
authors.lastname: Yaniv
authors.forename: Shai
authors.initials: S
authors.lastname: Uliel
authors.forename: Mark
authors.initials: M
authors.lastname: Katzenellenbogen
authors.forename: Joseph
authors.initials: J
authors.lastname: Riov
authors.forename: Ron
authors.initials: R
authors.lastname: Ophir
authors.forename: Einat
authors.initials: E
authors.lastname: Sadot
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D005052:Eucalyptus / Q000201:enzymology* / Q000254:growth & development; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D008969:Molecular Sequence Data; D050901:Nitrate Reductase / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D018517:Plant Roots / Q000254:growth & development*; D015854:Up-Regulation
chemical_list: D007210:Indoleacetic Acids; D009569:Nitric Oxide; C030737:indoleacetic acid; D050901:Nitrate Reductase