A gene essential for hydrotropism in roots

Akie Kobayashi, Akiko Takahashi, Yoko Kakimoto, Yutaka Miyazawa, Nobuharu Fujii, Atsushi Higashitani, Hideyuki Takahashi

Research output: Contribution to journalArticlepeer-review

132 Citations (Scopus)


Roots display hydrotropism in response to moisture gradients, which is thought to be important for controlling their growth orientation, obtaining water, and establishing their stand in the terrestrial environment. However, the molecular mechanism underlying hydrotropism remains unknown. Here, we report that roots of the Arabidopsis mutant mizu-kussei1 (miz1), which are impaired in hydrotropism, show normal gravitropism and elongation growth. The roots of miz1 plants showed reduced phototropism and a modified wavy growth response. There were no distinct differences in morphological features and root structure between miz1 and wild-type plants. These results suggest that the pathway inducing hydrotropism is independent of the pathways used in other tropic responses. The phenotype results from a single recessive mutation in MIZ1, which encodes a protein containing a domain (the MIZ domain) that is highly conserved among terrestrial plants such as rice and moss. The MIZ domain was not found in known genomes of organisms such as green algae, red algae, cyanobacteria, or animals. We hypothesize that MIZ1 has evolved to play an important role in adaptation to terrestrial life because hydrotropism could contribute to drought avoidance in higher plants. In addition, a pMIZ1::GUS fusion gene was expressed strongly in columella cells of the root cap but not in the elongation zone, suggesting that MIZ1 functions in the early phase of the hydrotropic response.

Original languageEnglish
Pages (from-to)4724-4729
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number11
Publication statusPublished - 2007 Mar 13


  • Arabidopsis
  • Columella cells
  • Drought avoidance
  • Root tropism


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