title: Tissue-specific expression of Populus C19 GA 2-oxidases differentially regulate above- and below-ground biomass growth through control of bioactive GA concentrations.
abstract: • Here, we studied the poplar C(19)  gibberellin 2-oxidase (GA2ox) gene subfamily. We show that a set of paralogous gene pairs differentially regulate shoot and root development. • PtGA2ox4 and its paralogous gene PtGA2ox5 are primarily expressed in aerial organs, and overexpression of PtGA2ox5 produced a strong dwarfing phenotype characteristic of GA deficiency. Suppression of PtGA2ox4 and PtGA2ox5 led to increased biomass growth, but had no effect on root development. By contrast, the PtGA2ox2 and PtGA2ox7 paralogous pair was predominantly expressed in roots, and when these two genes were RNAi-suppressed it led to a decrease of root biomass. • The morphological changes in the transgenic plants were underpinned by tissue-specific increases in bioactive GAs that corresponded to the predominant native expression of the targeted paralogous gene pair. Although RNAi suppression of both paralogous pairs led to changes in wood development, they were much greater in the transgenics with suppressed PtGA2ox4 and PtGA2ox5. The degree of gene suppression in independent events was strongly associated with phenotypes, demonstrating dose-dependent control of growth by GA2ox RNA concentrations. • The expression and transgenic modifications reported here show that shoot- and leaf-expressed PtGA2ox4 and PtGA2ox5 specifically restrain aerial shoot growth, while root-expressed PtGA2ox2 and PtGA2ox7 promote root development.
authors.affiliation: School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI 49931-1295, USA.
authors.forename: Jiqing
authors.initials: J
authors.lastname: Gou
authors.forename: Cathleen
authors.initials: C
authors.lastname: Ma
authors.forename: Mahita
authors.initials: M
authors.lastname: Kadmiel
authors.forename: Ying
authors.initials: Y
authors.lastname: Gai
authors.forename: Steven
authors.initials: S
authors.lastname: Strauss
authors.forename: Xiangning
authors.initials: X
authors.lastname: Jiang
authors.forename: Victor
authors.initials: V
authors.lastname: Busov
mesh_terms: D018533:Biomass; D015536:Down-Regulation / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D005875:Gibberellins / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D005810:Multigene Family / Q000235:genetics; D009928:Organ Specificity / Q000235:genetics*; D010641:Phenotype; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D032107:Populus / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development*; D034622:RNA Interference; D013489:Suppression, Genetic; D014934:Wood / Q000254:growth & development
chemical_list: D005875:Gibberellins; D007210:Indoleacetic Acids; D006899:Mixed Function Oxygenases; C121463:gibberellin 2-dioxygenase