title: Transgenic modification of gai or rgl1 causes dwarfing and alters gibberellins, root growth, and metabolite profiles in Populus.
abstract: In Arabidopsis and other plants, gibberellin (GA)-regulated responses are mediated by proteins including GAI, RGA and RGL1-3 that contain a functional DELLA domain. Through transgenic modification, we found that DELLA-less versions of GAI (gai) and RGL1 (rgl1) in a Populus tree have profound, dominant effects on phenotype, producing pleiotropic changes in morphology and metabolic profiles. Shoots were dwarfed, likely via constitutive repression of GA-induced elongation, whereas root growth was promoted two- to threefold in vitro. Applied GA(3 )inhibited adventitious root production in wild-type poplar, but gai/rgl1 poplars were unaffected by the inhibition. The concentrations of bioactive GA(1) and GA(4) in leaves of gai- and rgl1-expressing plants increased 12- to 64-fold, while the C(19) precursors of GA(1) (GA(53), GA(44) and GA(19)) decreased three- to ninefold, consistent with feedback regulation of GA 20-oxidase in the transgenic plants. The transgenic modifications elicited significant metabolic changes. In roots, metabolic profiling suggested increased respiration as a possible mechanism of the increased root growth. In leaves, we found metabolite changes suggesting reduced carbon flux through the lignin biosynthetic pathway and a shift towards allocation of secondary storage and defense metabolites, including various phenols, phenolic glucosides, and phenolic acid conjugates.
authors.affiliation: School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, 49931-1295, USA. vbusov@mtu.edu
authors.forename: Victor
authors.initials: V
authors.lastname: Busov
authors.forename: Richard
authors.initials: R
authors.lastname: Meilan
authors.forename: David W
authors.initials: DW
authors.lastname: Pearce
authors.forename: Stewart B
authors.initials: SB
authors.lastname: Rood
authors.forename: Caiping
authors.initials: C
authors.lastname: Ma
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Tschaplinski
authors.forename: Steven H
authors.initials: SH
authors.lastname: Strauss
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics*; D018533:Biomass; D015870:Gene Expression; D005875:Gibberellins / Q000378:metabolism* / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D018547:Plant Stems / Q000187:drug effects / Q000254:growth & development; D030821:Plants, Genetically Modified; D032107:Populus / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D046509:Tissue Culture Techniques
chemical_list: D029681:Arabidopsis Proteins; C109555:GAI protein, Arabidopsis; D005875:Gibberellins; C450824:RGL1 protein, Arabidopsis