title: Analysis of vascular development in the hydra sterol biosynthetic mutants of Arabidopsis.
abstract: BACKGROUND
  The control of vascular tissue development in plants is influenced by diverse hormonal signals, but their interactions during this process are not well understood. Wild-type sterol profiles are essential for growth, tissue patterning and signalling processes in plant development, and are required for regulated vascular patterning.
  
  
  RESULTS
  Here we investigate the roles of sterols in vascular tissue development, through an analysis of the Arabidopsis mutants hydra1 and fackel/hydra2, which are defective in the enzymes sterol isomerase and sterol C-14 reductase respectively. We show that defective vascular patterning in the shoot is associated with ectopic cell divisions. Expression of the auxin-regulated AtHB8 homeobox gene is disrupted in mutant embryos and seedlings, associated with variably incomplete vascular strand formation and duplication of the longitudinal axis. Misexpression of the auxin reporter proIAA2ratioGUS and mislocalization of PIN proteins occurs in the mutants. Introduction of the ethylene-insensitive ein2 mutation partially rescues defective cell division, localization of PIN proteins, and vascular strand development.
  
  
  CONCLUSIONS
  The results support a model in which sterols are required for correct auxin and ethylene crosstalk to regulate PIN localization, auxin distribution and AtHB8 expression, necessary for correct vascular development.
authors.affiliation: The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, Durham University, Durham, United Kingdom.
authors.forename: Margaret
authors.initials: M
authors.lastname: Pullen
authors.forename: Nick
authors.initials: N
authors.lastname: Clark
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Zarinkamar
authors.forename: Jennifer
authors.initials: J
authors.lastname: Topping
authors.forename: Keith
authors.initials: K
authors.lastname: Lindsey
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics; D001692:Biological Transport; D002455:Cell Division; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D013261:Sterols / Q000096:biosynthesis*
chemical_list: D029681:Arabidopsis Proteins; D005030:Ethylenes; D007210:Indoleacetic Acids; D013261:Sterols; C036216:ethylene
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