RESUMEN
In the present study an effort has been made to optimize the in vitro regeneration protocol for Agrobacterium-mediated transformation of Brassica juncea, because of its importance as oilseed crops. The highest callus induction frequency of 87% was observed on MS (Murashige and Skoog, 1962) medium supplemented with 4 µM 6-benzyladenine (BA) after four weeks of culture period. Subculturing of organogenic calli in MS media with a similar hormonal composition resulted in shoot organogenesis after six weeks of culture cultivation. The highest shoot induction frequency (92%) was recorded on MS medium containing 4 µM BA in combination with 1 µM of α-naphthalene acetic acid (NAA). Further, well-developed roots were formed in MS media augmented with 6 µM of Indole acetic acid (IAA) in combination with 1 µM Kinetin (Kn). Cotyledon explants were exploited in vitro for the successful transformation of B. juncea. A binary vector comprised of the Euonymus alatus diacylglycerol acetyltransferase (EaDAcT) gene under the transcriptional control of a glycinin promoter and with a basta selection marker was introduced into A. tumefaciens strain GV3101 via electroporation. EaDAcT gene is responsible for unusual triacylglycerol's production where the sn-3 position is esterified with acetate instead of the long-chain fatty acid found in the triacylglycerol's. The highest regeneration frequency (100%) of transgenic shoots was observed on MS medium supplemented with 4 µM BA plus 1 µM NAA in the presence of 25 mg l-1 basta and 160 mg l-1 timintin. The efficiency of stable transformation was found to be approximately 7% in the transgenic plants. Moreover, the transformed regenerated shoots were confirmed by PCR analysis using EaDAcT gene-specific primers.
