title: Overexpression of gibberellin 20-oxidase1 from Pinus densiflora results in enhanced wood formation with gelatinous fiber development in a transgenic hybrid poplar.
abstract: Gibberellins (GAs) are important regulators of plant shoot biomass growth, and GA 20-oxidase (GA20ox) is one of the major regulatory enzymes in the GA biosynthetic pathway. Previously, we showed that the expression levels of a putative GA20ox1 (i.e., PdGA20ox1) in stem tissue of 3-month-old seedlings of 12 families of Pinus densiflora were positively correlated with stem diameter growth across those same families growing in an even-aged 32-year-old pine forest (Park EJ, Lee WY, Kurepin LV, Zhang R, Janzen L, Pharis RP (2015) Plant hormone-assisted early family selection in Pinus densiflora via a retrospective approach. Tree Physiol 35:86-94). To further investigate the molecular function of this gene in the stem wood growth of forest trees, we produced transgenic poplar lines expressing PdGA20ox1 under the control of the 35S promoter (designated as 35S::PdGA20ox1). By age 3 months, most of the 35S::PdGA20ox1 poplar trees were showing an exceptional enhancement of stem wood growth, i.e., up to fourfold increases in stem dry weight, compared with the nontransformed control poplar plants. Significant increases in endogenous GA1, its immediate precursor (GA20) and its catabolite (GA8) in elongating internode tissue accompanied the increased stem growth in the transgenic lines. Additionally, the development of gelatinous fibers occurred in vertically grown stems of the 35S::PdGA20ox1 poplars. An analysis of the cell wall monosaccharide composition of the 35S::PdGA20ox1 poplars showed significant increases in xylose and glucose contents, indicating a qualitative increase in secondary wall depositions. Microarray analyses led us to find a total of 276 probe sets that were upregulated (using threefold as a threshold) in the stem tissues of 35S::PdGA20ox1 poplars relative to the controls. 'Cell organization or biogenesis'- and 'cell wall'-related genes were overrepresented, including many of genes that are involved in cell wall modification. Several transcriptional regulators, which positively regulate cell elongation through GA signaling, were also upregulated. In contrast, genes involved in defense signaling were appreciably downregulated in the 35S::PdGA20ox1 stem tissues, suggesting a growth versus defense trade-off. Taken together, our results suggest that PdGA20ox1 functions to promote stem growth and wood formation in poplar, probably by activating GA signaling while coincidentally depressing defense signaling.
authors.affiliation: Division of Forest Biotechnology, Korea Forest Research Institute, Suwon 441-847, Republic of Korea jhko@khu.ac.kr pahkej@forest.go.kr.
authors.forename: Eung-Jun
authors.initials: EJ
authors.lastname: Park
authors.affiliation: Division of Forest Biotechnology, Korea Forest Research Institute, Suwon 441-847, Republic of Korea.
authors.forename: Hyun-Tae
authors.initials: HT
authors.lastname: Kim
authors.affiliation: Division of Forest Biotechnology, Korea Forest Research Institute, Suwon 441-847, Republic of Korea.
authors.forename: Young-Im
authors.initials: YI
authors.lastname: Choi
authors.affiliation: Department of Plant and Environmental New Resources, Kyung Hee University, Yongin 446-701, Republic of Korea.
authors.forename: Chanhui
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Plant and Environmental New Resources, Kyung Hee University, Yongin 446-701, Republic of Korea.
authors.forename: Van Phap
authors.initials: VP
authors.lastname: Nguyen
authors.affiliation: Department of Plant and Environmental New Resources, Kyung Hee University, Yongin 446-701, Republic of Korea.
authors.forename: Hyung-Woo
authors.initials: HW
authors.lastname: Jeon
authors.affiliation: Division of Forest Biotechnology, Korea Forest Research Institute, Suwon 441-847, Republic of Korea Department of Plant and Environmental New Resources, Kyung Hee University, Yongin 446-701, Republic of Korea.
authors.forename: Jin-Seong
authors.initials: JS
authors.lastname: Cho
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Funada
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB, Canada T2N 1N4.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Pharis
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB, Canada T2N 1N4 Present address: Department of Biology, Western University, London, ON, Canada N6A 5B7.
authors.forename: Leonid V
authors.initials: LV
authors.lastname: Kurepin
authors.affiliation: Department of Plant and Environmental New Resources, Kyung Hee University, Yongin 446-701, Republic of Korea jhko@khu.ac.kr pahkej@forest.go.kr.
authors.forename: Jae-Heung
authors.initials: JH
authors.lastname: Ko
mesh_terms: D000040:Abscisic Acid / Q000096:biosynthesis; D018533:Biomass; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D005875:Gibberellins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D028223:Pinus / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D040081:Protein Array Analysis; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014934:Wood / Q000254:growth & development*
chemical_list: D005875:Gibberellins; D007210:Indoleacetic Acids; D018749:RNA, Plant; C030737:indoleacetic acid; D000040:Abscisic Acid; D006899:Mixed Function Oxygenases; C121463:gibberellin 2-dioxygenase
keywords: PdGA20ox1; gibberellins; growth versus defense trade-off; transgenic poplar