Origin of the Thiazole Ring of Camalexin, a Phytoalexin from Arabidopsis thaliana

Abstract

The principal phytoalexin that accumulates i n Arabidopsis fbaliana after infection by fungi or bacteria is 3-thiazol-2'-yl-indole (camalexin). Many plant species produce antimicrobial compounds, known as phytoalexins, after pathogen infection. In general, members of a particular plant family will produce phytoalexins that belong to the same class of compounds (Bailey and Mansfield, 1982). Leguminous plants produce isoflavanoid and/ or pterocarpan phytoalexins, whereas solanaceous plants produce sesquiterpenoid phytoalexins. AI1 of the phytoalexins that have been characterized from the members of the Brassicaceae are indole derivatives that are substituted at the C-3 position with a sulfur-containing moiety (Hammerschmidt et al., 1993). Conn et al. (1988) reported that Cumelina sativa (false flax) accumulated two different phytoalexins after infection with Alternaria brassicae, a funga1 pathogen of rapeseed. The most abundant of the two phytoalexins was identified

Complex Genetics Control Natural Variation inArabidopsis thalianaResistance toBotrytis cinerea

“…This locus is transcriptionally responsive to jasmonate and wounding and is predicted to influence availability of cysteine (Leon et al 1998;Jones et al 2003;Devoto et al 2005). Cysteine availability has the potential to influence camalexin accumulation through both camalexin biosynthesis and glutathionemediated signaling (Zook and Hammerschmidt 1997;Parisy et al 2007). Biochemical testing will be required to determine whether the single amino acid substitution in Shahdara significantly alters activity or regulation of this gene product.…”

Camalexin is synthesized from indole-3-acetaldoxime, a key branching point between primary and secondary metabolism in Arabidopsis

“…Fluorinated and 14 C-labeled tryptophan was incorporated with low efficiency. Low tryptophan incorporation has been observed in a study using 3 H-labeled tryptophan and anthranilate (8,9) and led to the suggestion that tryptophan was not a direct, or was at best a poor, precursor of camalexin. Generally, interpretation of in vivo labeling experiments is complicated by difference in the ability of compounds to be taken up and transported to the site of the biosynthetic machinery that might be localized to different compartments even for the same pathway.…”

“…These findings make camalexin a good model compound for studying biosynthesis and regulation of cruciferous indole phytoalexins. In vivo feeding experiments where radiolabeled anthranilate and tryptophan were applied on leaves treated with AgNO 3 led to the suggestion that tryptophan was not a precursor in camalexin biosynthesis because tryptophan was much less efficiently incorporated into camalexin compared with anthranilate (8,9). The data were further supported by labeling studies performed in three tryptophan mutants (8), where reduced levels of camalexin accumulated in trp1-100 with an impaired anthranilate transferase but not in trp3-1 and trp2-1 mutants with mutations in the ␣ and ␤ subunits of tryptophan synthase, respectively.…”

The Multifunctional Enzyme CYP71B15 (PHYTOALEXIN DEFICIENT3) Converts Cysteine-Indole-3-Acetonitrile to Camalexin in the Indole-3-Acetonitrile Metabolic Network ofArabidopsis thaliana

“…I3CHO was also suggested as biosynthetic intermediate in camalexin biosynthesis (Zook and Hammerschmidt, 1997). ESP, epithiospecifier protein.…”

“…Cys was shown to be the biosynthetic precursor of the thiazole ring of camalexin (excluding the 29 position) (Zook and Hammerschmidt, 1997). However, it was unclear whether Cys itself or rather a Cys metabolite is reacting with the indolic partner.…”