The TRANSPORT INHIBITOR RESPONSE2 gene is required for auxin synthesis and diverse aspects of plant development.
The plant hormone auxin plays an essential role in plant development. However, only a few auxin biosynthetic genes have been isolated and characterized. Here, we show that the TRANSPORT INHIBITOR RESPONSE2 (TIR2) gene is required for many growth processes. Our studies indicate that the tir2 mutant is hypersensitive to 5-methyl-tryptophan, an inhibitor of tryptophan synthesis. Further, treatment with the proposed auxin biosynthetic intermediate indole-3-pyruvic acid (IPA) and indole-3-acetic acid rescues the tir2 short hypocotyl phenotype, suggesting that tir2 may be affected in the IPA auxin biosynthetic pathway. Molecular characterization revealed that TIR2 is identical to the TAA1 gene encoding a tryptophan aminotransferase. We show that TIR2 is regulated by temperature and is required for temperature-dependent hypocotyl elongation. Further, we find that expression of TIR2 is induced on the lower side of a gravitropically responding root. We propose that TIR2 contributes to a positive regulatory loop required for root gravitropism.
Yamada
Masashi
M
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Greenham
Katie
K
Prigge
Michael J
MJ
Jensen
Philip J
PJ
Estelle
Mark
M
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D006358:Hot Temperature; D007210:Indoleacetic Acids / Q000378:metabolism*; D009154:Mutation; D010797:Phthalimides / Q000494:pharmacology; D010802:Phylogeny; D036226:Seedlings / Q000166:cytology / Q000378:metabolism; D051279:Tryptophan Transaminase / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D010797:Phthalimides; C002687:alpha-naphthylphthalamic acid; D051279:Tryptophan Transaminase