Reduction of polar auxin transport in tobacco by the tumorigenic Agrobacterium tumefaciens AK-6b gene

Yasutaka Kakiuchi, Ivan Gàlis, Shigeru Tamogami, Hiroetsu Wabiko

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


The plant-tumorigenic 6b (AK-6b) gene of Agrobacterium tumefaciens strain AKE10 induces morphological alterations to tobacco plants, Nicotiana tabacum. To investigate the molecular mechanisms underlying these processes, we generated transgenic tobacco harboring the AK-6b gene under the control of a dexamethazone-inducible promoter. Upon induction, transgenic tobacco seedlings exhibited distinct classes of aberrant morphologies, most notably adventitious outgrowths and stunted epicotyls. Histological analysis revealed massive proliferation and altered venation in the newly established outgrowths. Prominent vascular development suggested that auxin metabolism or signaling had been altered. Indeed, basipetal auxin transport in the hypocotyls of the transgenic seedlings was reduced by 50-80%, whereas intracellular auxin contents were only slightly reduced. Analysis of cell extracts by HPLC revealed a large accumulation of phenolic compounds, including the flavonoid kaempferol-3- rutinoside, in transgenic plants compared with wild-type seedlings. As some naturally occurring flavonoids have been shown to affect auxin transport, we suggest that the AK-6b gene expression impairs auxin transport via modulation of phenylpropanoid metabolism, and ultimately results in the observed morphological alterations.

Original languageEnglish
Pages (from-to)237-247
Number of pages11
Issue number2
Publication statusPublished - Jan 2006
Externally publishedYes


  • Agrobacterium
  • Auxin transport
  • Flavonoid
  • Morphological abnormality
  • Tobacco

ASJC Scopus subject areas

  • Genetics
  • Plant Science


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