The HAT2 gene, a member of the HD-Zip gene family, isolated as an auxin inducible gene by DNA microarray screening, affects auxin response in Arabidopsis.
The plant hormone, auxin, regulates many aspects of growth and development. Despite its importance, the molecular mechanisms underlying the action of auxin are largely unknown. To gain a more comprehensive understanding of the primary responses to auxin, we analyzed the expression of genes in Arabidopsis seedlings treated with indole-3-acetic acid (IAA) for 15 min. We identified a single gene that is downregulated early, and 29 genes that are upregulated early. Several types of typical transcription factors are identified as early upregulated genes, suggesting that auxin signals are mediated by a master set of diverse transcriptional regulators. Of the genes that responded to auxin, the expression of the homeobox gene, HAT2, was induced rapidly. Furthermore, we show that the expression of HAT2 is induced by auxin, but not by other phytohormones. To analyze the function of HAT2 in the plant's response to auxin, we generated 35S::HAT2 transgenic plants. These produced long hypocotyls, epinastic cotyledons, long petioles, and small leaves, which are characteristic of the phenotypes of the auxin-overproducing mutants, superroot1 (sur1) and superroot2 (sur2). On the other hand, 35S::HAT2 plants showed reduced lateral root elongation, and reduced auxin sensitivity compared to wild-type plants. Together with the results of RNA blotting and biochemical analyses, these findings suggest that HAT2 plays opposite roles in the shoot and root tissues in regulating auxin-mediated morphogenesis.
Sawa
Shinichiro
S
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Tokyo 113-0033, Japan. sawa@biol.s.u-tokyo.ac.jp
Ohgishi
Maki
M
Goda
Hideki
H
Higuchi
Kanako
K
Shimada
Yukihisa
Y
Yoshida
Shigeo
S
Koshiba
Tomokazu
T
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018398:Homeodomain Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D007210:Indoleacetic Acids / Q000494:pharmacology*; D016350:Leucine Zippers / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009280:Naphthaleneacetic Acids / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D010641:Phenotype; D010937:Plant Growth Regulators / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014158:Transcription, Genetic / Q000235:genetics
D029681:Arabidopsis Proteins; C473621:HAT2 protein, Arabidopsis; D018398:Homeodomain Proteins; D007210:Indoleacetic Acids; D009280:Naphthaleneacetic Acids; D010937:Plant Growth Regulators; C030737:indoleacetic acid