Variation of glucosinolate hydrolysis products in natural populations of Arabidopsis thaliana from Norway

During summer 2003, seeds from Arabidopsis thaliana growing wild in Norway were harvested from natural populations. A unique combination of temperature, photoperiod and light quality in Norway, not present anywhere else where populations of Arabidopsis occur, should lead to natural selection for specific alleles and genetic regulations of essential processes like vernalization, photomorphogenesis, flowering and seed production. Assuming that habitat and natural conditions such as long days (> 20 h day light during vegetation period) or altitude above 400 masl might also favour the development of distinct chemotypes, the glucosinolate (GLS) hydrolysis products of leaves of non-flowering, seed-grown individuals of in all 37 populations were analysed: 13 populations from Nordland county in North-Norway (latitude N 65-68, 3-110 masl), 11 from Oppland in Mid-Norway (latitude N 61, 400-850 masl), 1 from South-Trøndelag county (latitude N 63, 100 masl), 5 from Sogn- and Fjordane county (latitude N 61-62, 2-20 masl), 4 from Hedmark (latitude N 60, 100 masl), and 3 from Telemark county (latitude N 59, 400-500 masl). Despite the variability of environmental conditions of the corresponding habitats, high homogeneity could be observed when screening the plant collection for GLS hydrolysis products. Depending on epithiospecifier-protein (ESP) activity, most populations could be assigned to the epithionitrile-, alkenylisothiocyanate-type, or mixed types of both (Lambrix et al., 2001), based on the abundance of allyl and 3-butenyl GLS. Hydrolysis products from aliphatic and indolic GLS were present in all populations, whereas aromatic structures were restricted to only 5 accessions. In general, lower amounts of isothiocyanate products (ITC) were detected in plants derived from Nordland (1/3 reduction), compared to populations growing at high altitude (Oppland and Telemark), while simultaneously, nitrile levels were not affected that much. Methylthioalkyls (ITC and NIT products of 3-methylthiopropyl GLS, 6-methylthiohexyl GLS (only NIT), 7-methylthioheptyl GLS, and 8-methylthiooctyl GLS) and methylsulphinyls (NIT of 3-methylsulphinyl GLS) were present throughout all populations except for 6-methylthiohexyl ITC, which was mainly found in accessions from Oppland (high altitude). Distinct 3-butenyl GLS-rich accessions were accompanied by aromatic GLS structures, detected on the basis of hydrolysis products from 2-phenylethyl GLS (both ITC and NIT).