The short-rooted vitamin B6-deficient mutant pdx1 has impaired local auxin biosynthesis

Hao Chen, Liming Xiong*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

15 Citations (Scopus)


The phytohormone auxin regulates many aspects of plant growth and development. Auxin often acts distantly from the site of its biosynthesis and this long-distance-transported auxin is well known to play a critical role in eliciting physiological responses including regulating root development. Auxin can be produced in roots, yet the function of locally synthesized auxin in root growth is unclear. The major auxin in plants, indole 3-acetic acid (IAA), is mainly synthesized through tryptophan (Trp)-dependent pathways that require pyridoxal phosphate (an active form of vitamin B6)-dependent enzymes. We previously reported that the Arabidopsis vitamin B6 biosynthesis mutant pdx1 has stunted root growth although the underlying cause is unknown. Here we showed that the pdx1 root is deficient in auxin biosynthesis. By reciprocal grafting of pdx1 and the wild type, we demonstrated that the stunted root growth in pdx1 is caused by a locally generated signal(s) in roots. To test whether auxin might be one such signal, the auxin responsive DR5::GUS reporter was introduced into the mutant. The DR5::GUS activity in pdx1 root tips was greatly reduced compared with that in the wild type although the auxin response was unaltered. pdx1 also suppresses the root hair growth defects in the auxin overproduction mutant yucca. These data indicate that pdx1 is impaired in Trp-dependent auxin biosynthesis, which may contribute to the short-root phenotype of pdx1. We suggest that locally synthesized auxin may play a critical role in postembryonic root growth.

Original languageEnglish
Pages (from-to)1303-1310
Number of pages8
Issue number6
Publication statusPublished - May 2009

Scopus Subject Areas

  • Genetics
  • Plant Science

User-Defined Keywords

  • Auxin biosynthesis
  • Root growth
  • Stress
  • Tryptophan
  • Vitamin B6


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