Marker free approach for developing abiotic stress tolerant transgenic Brassica juncea (Indian mustard)

Use of selectable marker genes that confer resistance to transgenic plants on selection media is an extra burden on plant genome and also makes transgenic plants unacceptable to the consumer. The present study was taken to construct a novel vector for introducing, the glyoxalase I (gly I) gene under an inducible promoter to develop marker free salt tolerant Brassica juncea. The overexpression of the gly I gene has earlier been shown to impart salt and heavy metal stress tolerance in transgenic tobacco. The construct used in this investigation had the plant selectable marker gene npt II flanked by the loxP sites, together with the cre recombinase gene under the control of the beat-inducible (hsp) promoter. The gly I gene was cloned under a salt and drought inducible promoter (rd29A) so that it expressed only when the plant experienced stress. Using this novel construct, transgenic plants of Brassica juncea could be generated. The heat shock induction resulted in the excision of the intervening region between the two 34 bp loxP sites, which contained the npt H marker gene and the hsp-cre gene in the plants transformed with this vector. This strategy has been used to obtain marker free abiotic stress tolerant Brassica juncea, an economically useful oil yielding crop plant which could open the way for creating value added transgenic crops.