title: GNOM-mediated vesicular trafficking plays an essential role in hydrotropism of Arabidopsis roots.
abstract: Roots respond not only to gravity but also to moisture gradient by displaying gravitropism and hydrotropism, respectively, to control their growth orientation, which helps plants obtain water and become established in the terrestrial environment. As gravitropism often interferes with hydrotropism, however, the mechanisms of how roots display hydrotropism and differentiate it from gravitropism are not understood. We previously reported MIZU-KUSSEI1 (MIZ1) as a gene required for hydrotropism but not for gravitropism, although the function of its protein was not known. Here, we found that a mutation of GNOM encoding guanine-nucleotide exchange factor for ADP-ribosylation factor-type G proteins was responsible for the ahydrotropism of Arabidopsis (Arabidopsis thaliana), miz2. Unlike other gnom alleles, miz2 showed no apparent morphological defects or reduced gravitropism. Instead, brefeldin A (BFA) treatment inhibited both hydrotropism and gravitropism in Arabidopsis roots. In addition, a BFA-resistant GNOM variant, GNM696L, showed normal hydrotropic response in the presence of BFA. Furthermore, a weak gnom allele, gnomB/E, showed defect in hydrotropic response. These results indicate that GNOM-mediated vesicular trafficking plays an essential role in hydrotropism of seedling roots.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Miyazawa
authors.forename: Akiko
authors.initials: A
authors.lastname: Takahashi
authors.forename: Akie
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kaneyasu
authors.forename: Nobuharu
authors.initials: N
authors.lastname: Fujii
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D014644:Genetic Variation; D018522:Gravitropism / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D018517:Plant Roots / Q000254:growth & development / Q000502:physiology*; D036226:Seedlings / Q000502:physiology*; D016415:Sequence Alignment; D018523:Tropism / Q000502:physiology; D014867:Water / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C088087:GNOM protein, Arabidopsis; D020662:Guanine Nucleotide Exchange Factors; C519512:mizu-kussei1 protein, Arabidopsis; D014867:Water