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Abstract

UV-B irradiation changes specifically the secondary metabolite profile in broccoli sprouts – induced signalling overlaps with the plant response to biotic stressors.

Only a few environmental factors have such a pronounced effect on plant growth and development as ultraviolet light (UV). Concerns have arisen due to increased UV-B radiation reaching the earth surface as a result of stratospheric ozone depletion. Ecologically relevant low to moderate UV-B doses (0.3 – 1 kJ m-2 d-1) were applied to sprouts of the important vegetable crop B. oleracea var. italica (broccoli) and eco-physiological responses such as accumulation of non-volatile secondary metabolites were related to transcriptional responses with Agilent One-Color Gene Expression Microarray analysis using the 2 x 204 k format Brassica microarray. UV-B radiation effects have been usually linked to increases in phenolic compounds. As expected, the flavonoids kaempferol and quercetin accumulated in broccoli sprouts (aerial part of seedlings) 24 hours after UV-B treatment. A new finding is the specific UV-B-mediated induction of glucosinolates (GS), especially of 4-methylsulfinylbutyl GS and 4-methoxy-indol-3-ylmethyl GS, while carotenoids and chlorophyll levels remained unaffected. Accumulation of defensive GS metabolites was accompanied by increased expression of genes associated with salicylate and jasmonic acid signaling defense pathways and up-regulation of genes responsive to fungal and bacterial pathogens. Concomitantly, plant pre-exposure to moderate UV-B doses had negative effects on the performance of the caterpillar Pieris brassicae (L.) and on the population growth of the aphid Myzus persicae (Sulzer). Moreover, insect-specific induction of GS in broccoli sprouts was affected by UV-B pretreatment.



Mewis, I.; Schreiner, M.; Nguyen, C.N.; Krumbein, A.; Ulrichs, C.; Lohse, M.; Zrenner, R. 2012. UV-B irradiation changes specifically the secondary metabolite profile in broccoli sprouts – Induced signalling overlaps with the plant response to biotic stressors. Plant and Cell Physiology 53 (9), 1546-1560.