Biochemical Genetics of Plant Secondary Metabolites in Arabidopsis thaliana

Abstract

Mutants of Arabidopsis thaliana with a glucosinolate content different from wild type were isolated by screening a mutagenized population of plants. Six mutants were detected out of a population of 1200 screened. One of these mutants, TUI, was analyzed in detail. Leaf and seed tissues of line TUl lack or have reduced amounts of many of the aliphatic glucosinolates found in the wild type due to a recessive allele, gsml, of a single nuclear gene, GSM1. The seed phenotype is inherited as a maternal effect suggesting that the embryo is dependent on the maternal tissue for its glucosinolates. Experiments involving feeding of "4C-labeled intermediates suggested that the gsml allele results in a metabolic block which decreases the availability of several amino acid substrates required for glucosinolate biosynthesis: 2-amino-6-methylthiohexanoic acid, 2-amino-7-methylthioheptanoic acid, and 2-amino-8-methylthiooctanoic acid. The mutation does not result in any obvious changes in morphology or growth rate. A pathway for the biosynthesis of glucosinolates in A. thaliana is proposed.Glucosinolates are anionic thioglucosides (Fig. 1) synthesized by many species of the order Capparales including all the Brassicaceae (for reviews see refs. 6 and 26). The primary biological function of glucosinolates is unknown, although a role in plant defense against bacterial and fungal pathogens and insect predators has been suggested (reviewed by Fenwick et al. [6]).The presence of glucosinolates in crop species has several important consequences. First, dietary problems in livestock can result when fodder with high levels of glucosinolates are consumed. Thus, glucosinolates severely restrict the amount of glucosinolate-containing meal that can be used in animal feed supplements (24). Second, the distinctive flavor associated with Brassicaceae species which serve as vegetable and

Genetics of aliphatic glucosinolates. I. Side chain elongation in Brassica napus and Arabidopsis thaliana

“…The similar results obtained with the single-marker and hydroxypropyl glucosinolates while Columbia con-tamed methylsuiphinylbutyl glucosinolate and trace levels of methylsulphinylpropyl glucosinolate (Fig. 8) and other homologues with longer side chain lengths, as reported previously (Haughn et al, 1991). Within the F2 and RI populations, four discrete classes of glucosinolate phenotypes were observed (Fig.…”

“…Aliphatic glucosinolate profiles vary between wildtype accessions of A. thaliana and in leaves comprise alkenyl, methylthioalkyl, methylsuphinylalkenyl and hydroxyalkyl homologues of propyl and butyl glucosinolates, with trace levels of other homologues with longer side chain lengths (Hogge et al, 1988;Haughn et a!., 1991). By analogy with studies in Brassica, a model can be developed that explains the variation in aliphatic glucosinolates on the basis of variation in…”

Mathematical modelling of aliphatic glucosinolate chain length distribution in Arabidopsis thaliana leaves

“…MAM1 mutants also show an interesting glucosinolate profile: whereas C 4 glucosinolates are dominant in wild-type plants, in MAM1 missense or knockout mutants C 3 glucosinolates are more abundant (Haughn et al 1991;Kroymann et al 2001;Textor et al 2007). The glucosinolate profile of a plant line in which the MAM1 gene is disrupted by a T-DNA insertion (gsm1-3) was examined by Textor et al (2007).…”

Functional Analysis of the Tandem-Duplicated P450 Genes SPS/BUS/CYP79F1 and CYP79F2 in Glucosinolate Biosynthesis and Plant Development by Ds Transposition-Generated Double Mutants

“…Detection was performed at 229 nm and 260 nm using a photodiode array. Desulphoglucosinolates were quantified based on response factors (Buchner, 1987;Haughn et al, 1991) and an internal p-hydroxybenzylglucosinolate (Bioraf, Akirkeby, Denmark) standard as previously described (Petersen et al, 2001(Petersen et al, , 2002. The standard was added at the beginning of the extraction procedure.…”