5-(4-chlorophenyl)-4h-1-2-4-triazole-3-thiol and indoleacetic-acid

The plant hormone indole-3-acetic acid (IAA) is one of the main signals playing a role in the communication between host and endophytes. Endophytes can synthesize IAA de novo to influence the IAA homeostasis in plants. Although much is known about IAA biosynthesis in microorganisms, there is still less known about the pathway by which IAA is synthesized in fungal endophytes. The aim of this study is to examine a possible IAA biosynthesis pathway in

Topics: Arabidopsis; Arabidopsis Proteins; Ascomycota; Benzimidazoles; Culture Media, Conditioned; Endophytes; Genome, Fungal; Glycolates; Host Adaptation; Host Specificity; Indoleacetic Acids; Indoles; Metabolic Networks and Pathways; Phthalimides; Plant Roots; Triazoles; Tryptophan

Despite the existence of considerable research on somatic embryogenesis (SE), the molecular mechanism that regulates the biosynthesis of auxins during the SE induction process remains unknown. Indole-3-acetic acid (IAA) is an auxin that is synthesized in plants through five pathways. The biosynthetic pathway most frequently used in this synthesis is the conversion of tryptophan to indol-3-pyruvic acid (IPA) by tryptophan aminotransferase of

Topics: Biosynthetic Pathways; Coffea; Enzyme Inhibitors; Gene Expression Profiling; Genes, Plant; Indoleacetic Acids; Mixed Function Oxygenases; Multigene Family; Plant Growth Regulators; Plant Proteins; Plant Somatic Embryogenesis Techniques; Triazoles

Gravitropism refers to the growth or movement of plants that is influenced by gravity. Roots exhibit positive gravitropism, and the root cap is thought to be the gravity-sensing site. In some plants, the root cap requires light irradiation for positive gravitropic responses. However, the mechanisms regulating this phenomenon are unknown. We herein report that maize roots exposed to white light continuously for ≥1-2h show increased indole-3-acetic acid (IAA) levels in the root tips, especially in the transition zone (1-3mm from the tip). Treatment with IAA biosynthesis inhibitors yucasin and l-kynurenine prevented any increases in IAA content and root curvature under light conditions. Analyses of the incorporation of a stable isotope label from tryptophan into IAA revealed that some of the IAA in roots was synthesized in the root apex. Furthermore, Zmvt2 and Zmyuc gene transcripts were detected in the root apex. One of the Zmyuc genes (ZM2G141383) was up-regulated by light irradiation in the 0-1mm tip region. Our findings suggest that IAA accumulation in the transition zone is due to light-induced activation of Zmyuc gene expression in the 0-1mm root apex region. Light-induced changes in IAA levels and distributions mediate the maize root gravitropic U-turn.

Topics: Gene Expression Regulation, Plant; Gravitropism; Indoleacetic Acids; Kynurenine; Light; Meristem; Metabolic Networks and Pathways; Plant Growth Regulators; Plant Root Cap; Triazoles; Zea mays

Indole-3-acetic acid (IAA), an auxin plant hormone, is biosynthesized from tryptophan. The indole-3-pyruvic acid (IPyA) pathway, involving the tryptophan aminotransferase TAA1 and YUCCA (YUC) enzymes, was recently found to be a major IAA biosynthetic pathway in Arabidopsis. TAA1 catalyzes the conversion of tryptophan to IPyA, and YUC produces IAA from IPyA. Using a chemical biology approach with maize coleoptiles, we identified 5-(4-chlorophenyl)-4H-1,2,4-triazole-3-thiol (yucasin) as a potent inhibitor of IAA biosynthesis in YUC-expressing coleoptile tips. Enzymatic analysis of recombinant AtYUC1-His suggested that yucasin strongly inhibited YUC1-His activity against the substrate IPyA in a competitive manner. Phenotypic analysis of Arabidopsis YUC1 over-expression lines (35S::YUC1) demonstrated that yucasin acts in IAA biosynthesis catalyzed by YUC. In addition, 35S::YUC1 seedlings showed resistance to yucasin in terms of root growth. A loss-of-function mutant of TAA1, sav3-2, was hypersensitive to yucasin in terms of root growth and hypocotyl elongation of etiolated seedlings. Yucasin combined with the TAA1 inhibitor l-kynurenine acted additively in Arabidopsis seedlings, producing a phenotype similar to yucasin-treated sav3-2 seedlings, indicating the importance of IAA biosynthesis via the IPyA pathway in root growth and leaf vascular development. The present study showed that yucasin is a potent inhibitor of YUC enzymes that offers an effective tool for analyzing the contribution of IAA biosynthesis via the IPyA pathway to plant development and physiological processes.

Topics: Arabidopsis; Arabidopsis Proteins; Biosynthetic Pathways; Cotyledon; Dose-Response Relationship, Drug; Gene Expression Regulation, Plant; Indoleacetic Acids; Indoles; Mutation; Oxygenases; Phenotype; Plant Growth Regulators; Plant Leaves; Plant Roots; Plant Shoots; Plants, Genetically Modified; Recombinant Fusion Proteins; Seedlings; Small Molecule Libraries; Triazoles; Tryptophan Transaminase; Zea mays