title: The glutathione-deficient mutant pad2-1 accumulates lower amounts of glucosinolates and is more susceptible to the insect herbivore Spodoptera littoralis.
abstract: Summary Plants often respond to pathogen or insect attack by inducing the synthesis of toxic compounds such as phytoalexins and glucosinolates (GS). The Arabidopsis mutant pad2-1 has reduced levels of the phytoalexin camalexin and is known for its increased susceptibility to fungal and bacterial pathogens. We found that pad2-1 is also more susceptible to the generalist insect Spodoptera littoralis but not to the specialist Pieris brassicae. The PAD2 gene encodes a gamma-glutamylcysteine synthetase that is involved in glutathione (GSH) synthesis, and consequently the pad2-1 mutant contains about 20% of the GSH found in wild-type plants. Lower GSH levels of pad2-1 were correlated with reduced accumulation of the two major indole and aliphatic GSs of Arabidopsis, indolyl-3-methyl-GS and 4-methylsulfinylbutyl-GS, in response to insect feeding. This effect was specific to GSH, was not complemented by treatment of pad2-1 with the strong reducing agent dithiothreitol, and was not observed with the ascorbate-deficient mutant vtc1-1. In contrast to the jasmonate-insensitive mutant coi1-1, expression of insect-regulated and GS biosynthesis genes was not affected in pad2-1. Our data suggest a crucial role for GSH in GS biosynthesis and insect resistance.
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Klaus
authors.initials: K
authors.lastname: Schlaeppi
authors.forename: Natacha
authors.initials: N
authors.lastname: Bodenhausen
authors.forename: Antony
authors.initials: A
authors.lastname: Buchala
authors.forename: Felix
authors.initials: F
authors.lastname: Mauch
authors.forename: Philippe
authors.initials: P
authors.lastname: Reymond
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D005961:Glucosinolates / Q000096:biosynthesis*; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D018411:Spodoptera / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D005961:Glucosinolates; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione