Identification of cadmium-regulated genes by cDNA-AFLP in the heavy metal accumulator Brassica juncea L.

In this study, cDNA-amplified fragment length polymorphism (cDNA-AFLP) analysis was employed to identify genes that exhibited a modulated expression following cadmium (Cd) treatment in Brassica juncea grown in hydroponic culture. Plants were treated for 6 h, 24 h, and 6 weeks with 10 mu M Cd(NO3)(2) and untreated 6-week-old plants were used as controls. Cd content was measured at these four time points. Long exposure to Cd affected root morphology: roots appeared thinner and sent out side roots. Seventy-three transcript-derived fragments were identified as Cd responsive. Fifty-two of them showed significant homology to genes with known or putative function, 10 transcript-derived fragments were homologous to uncharacterized genes, while 11 transcript-derived fragments did not show significant matches. The expression pattern of several of these genes was confirmed by northern blot analysis. Fifty-two genes of known or putative function were transcriptional factors, expression regulators, and stress responding and transport facilitation genes, as well as genes involved in cellular metabolism and organization and the photosynthetic process, suggesting that a multitude of processes are implicated in Cd stress response. The transcription of drought- and abscisic acid-responsive genes observed in this study also suggested that Cd imposes water stress and that abscisic acid may be involved in the Cd plant response.