title: Engineering of gibberellin levels in citrus by sense and antisense overexpression of a GA 20-oxidase gene modifies plant architecture.
abstract: Carrizo citrange (Citrus sinensisxPoncirus trifoliata) is a citrus hybrid widely used as a rootstock, whose genetic manipulation to improve different growth characteristics is of high agronomic interest. In this work, transgenic Carrizo citrange plants have been produced overexpressing sense and antisense CcGA20ox1 (a key enzyme of GA biosynthesis) under control of the 35S promoter to modify plant architecture. As expected, taller (sense) and shorter (antisense) phenotypes correlated with higher and lower levels, respectively, of active GA1 in growing shoots. In contrast, other phenotypic characteristics seemed to be specific to citrus, or different from those described for similar transgenics in other species. For instance, thorns, typical organs of citrus at juvenile stages, were much longer in sense and shorter in antisense plants, and xylem tissue was reduced in leaf and internode of sense plants. Antisense plants presented a bushy phenotype, suggesting a possible effect of GAs on auxin biosynthesis and/or transport. The main foliole of sense plants was longer, although total leaf area was reduced. Leaf thickness was smaller in sense and larger in antisense plants due to changes in the spongy parenchyma. Internode cell length was not altered in transgenic plants, indicating that, in citrus, GAs regulate cell division rather than cell elongation. Interestingly, the phenotypes described were not apparent when transgenic plants were grafted on non-transgenic rootstock. This suggests that roots contribute to the GA economy of aerial parts in citrus and opens the possibility of using the antisense plants as dwarfing rootstocks.
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Apdo. Oficial, Moncada 46113, Valencia, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Fagoaga
authors.forename: Francisco R
authors.initials: FR
authors.lastname: Tadeo
authors.forename: Domingo J
authors.initials: DJ
authors.lastname: Iglesias
authors.forename: Laura
authors.initials: L
authors.lastname: Huerta
authors.forename: Ignacio
authors.initials: I
authors.lastname: Lliso
authors.forename: Ana M
authors.initials: AM
authors.lastname: Vidal
authors.forename: Manuel
authors.initials: M
authors.lastname: Talon
authors.forename: Luís
authors.initials: L
authors.lastname: Navarro
authors.forename: José L
authors.initials: JL
authors.lastname: García-Martínez
authors.forename: Leandro
authors.initials: L
authors.lastname: Peña
mesh_terms: D002957:Citrus / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D016373:DNA, Antisense / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005818:Genetic Engineering; D005822:Genetic Vectors; D005875:Gibberellins / Q000235:genetics*; D006899:Mixed Function Oxygenases / Q000235:genetics*; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics; D030821:Plants, Genetically Modified / Q000502:physiology; D018749:RNA, Plant / Q000235:genetics; D015183:Restriction Mapping
chemical_list: D016373:DNA, Antisense; D018744:DNA, Plant; D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D018749:RNA, Plant; D006899:Mixed Function Oxygenases; C089210:gibberellin, 2-oxoglutarate-oxygen oxidoreductase (20-hydroxylating, oxidizing)