Mutation of a UDP-glucose-4-epimerase alters nematode susceptibility and ethylene responses in Arabidopsis roots

• Published in: The Plant journal : for cell and molecular biology Vol. 40; no. 5; pp. 712 - 724
• Main Authors: Wubben, M.J.E. II, Rodermel, S.R, Baum, T.J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.12.2004; Blackwell Science; Blackwell Publishing Ltd
• Subjects: Amino Acids, Cyclic - metabolism; Amino Acids, Cyclic - pharmacology; Animals; Arabidopsis; Arabidopsis - drug effects; Arabidopsis - parasitology; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; auxin; auxin transport protein EIR1; Biological and medical sciences; Botany; Culture Media; cyst nematodes; Down-Regulation; Enzymes; Ethylene; ethylene sensitivity; Ethylenes - metabolism; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Plant; gene-for-gene relationship; Glucose; Heterodera schachtii; host-parasite relationships; hypersensitive response; indole acetic acid; Indoleacetic Acids - pharmacology; isomerases; messenger RNA; molecular sequence data; Mutation; Nematoda - physiology; nematode; nucleotide sequences; Phenotype; phenotypic variation; physiological response; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - genetics; Plant Growth Regulators - physiology; plant response; Plant Roots - growth & development; Plant Roots - metabolism; Protozoa. Invertebrates; Records, symptoms, damages, economic importance, population surveys; root growth; roots; Sensitivity; Signal Transduction; transport proteins; UDP-glucose-4-epimerase; UDPglucose 4-Epimerase - genetics; UDPglucose 4-Epimerase - metabolism; Worms; Heteroderidae; Ethylene; Structure function relationship; Arabidopsis thaliana; Signal transduction; Pest; Isomerases; Gene; Cruciferae; Dicotyledones; UDPglucose 4-epimerase; Angiospermae; Nematoda; ethylene sensitivity; nematode; auxin; Enzyme; Sensitivity; Helmintha; Nemathelminthia; Spermatophyta; Mutation; Invertebrata; Experimental plant; Heterodera schachtii
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2004.02257.x

Summary In Arabidopsis, mutation of RHD1, a UDP‐glucose‐4‐epimerase, causes root‐specific phenotypes, including hypersusceptibility to the cyst nematode Heterodera schachtii, increased root hair elongation, decreased root length, and root epidermal bulging. Previous experiments suggested that increased ethylene sensitivity or production mediated the rhd1‐4 phenotypes. In the present study, double mutant analyses revealed that only rhd1‐4 hypersusceptibility to H. schachtii and increased root hair elongation were dependent upon the ethylene signaling genes EIN2 and EIN3 but not upon ethylene signaling mediated by the auxin efflux carrier EIR1. In contrast, the rhd1‐4 short root and root epidermal bulging phenotypes did not require EIN2, EIN3, or EIR1. A time‐course analysis of RHD1 transcript levels in wild‐type plants treated with the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid showed a root‐specific downregulation of RHD1 expression by ethylene. This observation was corroborated by our finding of increased RHD1 transcript levels in roots of the ethylene‐insensitive mutants etr1 and ein2. In addition to ethylene, auxin strongly influences H. schachtii susceptibility and root hair elongation. Therefore, we investigated the sensitivity of rhd1‐4 roots to indole‐3‐acetic acid (IAA). Equivalent IAA concentrations caused a greater reduction in rhd1‐4 root elongation compared with wild‐type roots. Finally, H. schachtii parasitism was found to strongly downregulate RHD1 expression in the root 3 days after inoculation. We conclude that RHD1 is a likely target of root‐specific negative regulation by ethylene and that loss of RHD1 function results in a heightened sensitivity of root tissues to both ethylene and auxin.