title: Heterologous expression and transcript analysis of gibberellin biosynthetic genes of grasses reveals novel functionality in the GA3ox family.
abstract: BACKGROUND
  The gibberellin (GA) pathway plays a central role in the regulation of plant development, with the 2-oxoglutarate-dependent dioxygenases (2-ODDs: GA20ox, GA3ox, GA2ox) that catalyse the later steps in the biosynthetic pathway of particularly importance in regulating bioactive GA levels. Although GA has important impacts on crop yield and quality, our understanding of the regulation of GA biosynthesis during wheat and barley development remains limited. In this study we identified or assembled genes encoding the GA 2-ODDs of wheat, barley and Brachypodium distachyon and characterised the wheat genes by heterologous expression and transcript analysis.
  
  
  RESULTS
  The wheat, barley and Brachypodium genomes each contain orthologous copies of the GA20ox, GA3ox and GA2ox genes identified in rice, with the exception of OsGA3ox1 and OsGA2ox5 which are absent in these species. Some additional paralogs of 2-ODD genes were identified: notably, a novel gene in the wheat B genome related to GA3ox2 was shown to encode a GA 1-oxidase, named as TaGA1ox-B1. This enzyme is likely to be responsible for the abundant 1β-hydroxylated GAs present in developing wheat grains. We also identified a related gene in barley, located in a syntenic position to TaGA1ox-B1, that encodes a GA 3,18-dihydroxylase which similarly accounts for the accumulation of unusual GAs in barley grains. Transcript analysis showed that some paralogs of the different classes of 2-ODD were expressed mainly in a single tissue or at specific developmental stages. In particular, TaGA20ox3, TaGA1ox1, TaGA3ox3 and TaGA2ox7 were predominantly expressed in developing grain. More detailed analysis of grain-specific gene expression showed that while the transcripts of biosynthetic genes were most abundant in the endosperm, genes encoding inactivation and signalling components were more highly expressed in the seed coat and pericarp.
  
  
  CONCLUSIONS
  The comprehensive expression and functional characterisation of the multigene families encoding the 2-ODD enzymes of the GA pathway in wheat and barley will provide the basis for a better understanding of GA-regulated development in these species. This analysis revealed the existence of a novel, endosperm-specific GA 1-oxidase in wheat and a related GA 3,18-dihydroxylase enzyme in barley that may play important roles during grain expansion and development.
authors.affiliation: Department of Plant Sciences, University of California, Davis, CA, 95616, USA. sppearce@ucdavis.edu.
authors.forename: Stephen
authors.initials: S
authors.lastname: Pearce
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. alison.huttly@rothamsted.ac.uk.
authors.forename: Alison K
authors.initials: AK
authors.lastname: Huttly
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. ian.prosser@gmx.com.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Prosser
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. liyidan@foxmail.com.|Biotechnology Research Centre, Jilin Academy of Agricultural Sciences, Changchun, 130033, China. liyidan@foxmail.com.
authors.forename: Yi-dan
authors.initials: YD
authors.lastname: Li
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. simon.vaughan@rothamsted.ac.uk.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Vaughan
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. bylynka14@hotmail.com.
authors.forename: Barbora
authors.initials: B
authors.lastname: Gallova
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. archana.patil@rothamsted.ac.uk.
authors.forename: Archana
authors.initials: A
authors.lastname: Patil
authors.affiliation: University of Bristol Transcriptomics Facility, School of Biological Sciences, Bristol, BS8 1UG, UK. jane.coghill@bristol.ac.uk.
authors.forename: Jane A
authors.initials: JA
authors.lastname: Coghill
authors.affiliation: Department of Plant Sciences, University of California, Davis, CA, 95616, USA. jdubcovsky@ucdavis.edu.|Howard Hughes Medical Institute, Chevy Chase, MD, 20815, USA. jdubcovsky@ucdavis.edu.
authors.forename: Jorge
authors.initials: J
authors.lastname: Dubcovsky
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. peter.hedden@rothamsted.ac.uk.
authors.forename: Peter
authors.initials: P
authors.lastname: Hedden
authors.affiliation: Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, AL5 2JQ, UK. andy.phillips@rothamsted.ac.uk.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Phillips
mesh_terms: D055162:Biocatalysis; D053898:Biosynthetic Pathways / Q000235:genetics*; D058431:Brachypodium / Q000201:enzymology / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005875:Gibberellins / Q000096:biosynthesis*; D001467:Hordeum / Q000201:enzymology / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000235:genetics*; D005810:Multigene Family; D012275:Oryza / Q000201:enzymology / Q000235:genetics; D010802:Phylogeny; D006109:Poaceae / Q000201:enzymology* / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017423:Sequence Analysis, RNA; D015398:Signal Transduction / Q000235:genetics; D014908:Triticum / Q000201:enzymology / Q000235:genetics
chemical_list: D005875:Gibberellins; D012333:RNA, Messenger; D006899:Mixed Function Oxygenases