title: Elevated auxin and reduced cytokinin contents in rootstocks improve their performance and grafting success.
abstract: Plant grafting is an important technique for horticultural and silvicultural production. However, many rootstock plants suffer from undesirable lateral bud outgrowth, low grafting success rates or poor rooting. Here, we used a root-predominant gene promoter (SbUGT) to drive the expression of a tryptophan-2-monooxygenase gene (iaaM) from Agrobacterium tumefaciens to increase auxin levels in tobacco. The transgenic plants, when used as a rootstock, displayed inhibited lateral bud outgrowth, enhanced grafting success rate and improved root initiation. However, root elongation and biomass of SbUGT::iaaM transgenic plants were reduced compared to those of wild-type plants. In contrast, when we used this same promoter to drive CKX (a cytokinin degradation gene) expression, the transgenic tobacco plants displayed enhanced root elongation and biomass. We then made crosses between the SbUGT::CKX and SbUGT::iaaM transgenic plants. We observed that overexpression of the CKX gene neutralized the negative effects of auxin overproduction on root elongation. Also, the simultaneous expression of both the iaaM and CKX genes in rootstock did not disrupt normal growth and developmental patterns in wild-type scions. Our results demonstrate that expression of both the iaaM and CKX genes predominantly in roots of rootstock inhibits lateral bud release from rootstock, improves grafting success rates and enhances root initiation and biomass.
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, USA.
authors.forename: Chu
authors.initials: C
authors.lastname: Fang
authors.affiliation: Department of Crop Science, Michigan State University, East Lansing, MI, USA.
authors.forename: Sanalkumar
authors.initials: S
authors.lastname: Krishnan
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, USA.
authors.forename: Junmei
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA.
authors.forename: Angus S
authors.initials: AS
authors.lastname: Murphy
authors.affiliation: Department of Crop Science, Michigan State University, East Lansing, MI, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Merewitz
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, USA.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Katin-Grazzini
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: McAvoy
authors.affiliation: College of Horticulture, Hunan Agricultural University, Changsha, Hunan, China.
authors.forename: Ziniu
authors.initials: Z
authors.lastname: Deng
authors.affiliation: Plant Pathology Department, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA.
authors.forename: Janice
authors.initials: J
authors.lastname: Zale
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, USA.|College of Horticulture, Hunan Agricultural University, Changsha, Hunan, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D003583:Cytokinins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics*; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D014026:Nicotiana / Q000235:genetics* / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D003583:Cytokinins; D007210:Indoleacetic Acids; D010940:Plant Proteins; C081170:iaaM protein, Agrobacterium; D010088:Oxidoreductases; C019984:cytokinin oxidase
keywords: auxin; cytokinins; grafting success rate; lateral buds release; root growth and development; rootstock