The Brassica juncea BjCdR15, an ortholog ofArabidopsis TGA3, is a regulator of cadmium uptake,transport and accumulation in shoots and confers cadmium tolerance in transgenic plants

摘要

A bZIP transcription factor from Brassica juncea (BjCdR15) was isolated by\udthe cDNA-amplified fragment length polymorphism technique after cadmium\udtreatment. Sequence analysis indicated high similarity between BjCdR15 and Arabidopsis\udTGA3. In Arabidopsis, TGA3 transcription is also induced by cadmium;\udhence, we investigated whether BjCdR15 is involved in cadmium tolerance and\udwhether it can functionally replace TGA3 protein in Arabidopsis tga3-2 mutant\udplants.\ud• BjCdR15 expression was detected mainly in the epidermis and vascular system\udof cadmium-treated plants, and increased in roots and leaves after cadmium treatment.\udThe overexpression of BjCdR15 in Arabidopsis and tobacco enhanced cadmium\udtolerance: overexpressing plants showed high cadmium accumulation in\udshoots. Conversely, Arabidopsis tga3-2 mutant plants showed high cadmium content\udin roots and inhibition of its transport to the shoot.\ud• We demonstrated that BjCdR15 can functionally replace TGA3: in 35S::\udBjCdR15-tga3-2 plants, the long-distance transport of cadmium from root to\udshoot was restored and these plants showed an increased cadmium content in\udshoots compared with all other assays. In addition, BjCdR15 ⁄ TGA3 regulated\udthe synthesis of phytochelatin synthase and the expression of several metal\udtransporters.\ud• The results indicate that BjCdR15 ⁄ TGA3 transcription factors play a crucial role\udin the regulation of cadmium uptake by roots and in its long-distance root to shoot\udtransport. BjCdR15 ⁄ TGA3 may thus be considered as useful candidates for potential\udbiotechnological applications in the phytoextraction of cadmium from polluted\udsoils.