A full-length 956 by gene coding for a defensin (BjD) with an open reading frame of 243 by capable of coding for a peptide of 81 amino acids was cloned from mustard (Brassica juncea). Iso-electric point and the molecular mass of the deduced BjD protein were predicted to be 8.7 and 8.61 kD, respectively. This gene is expressed only in leaves of the mustard plant and its expression is upregulated by various abiotic stress inducers, methyl viologen and hydrogen peroxide. This gene is also upregulated by salicylic acid, abscisic acid, ethephon and wounding. The partially characterized upstream regulatory region of the gene possessed a number of conserved elements that were shown earlier to be important in stress induced upregulation of various genes. These observations indicate that this gene has potential in inducing biotic and abiotic stress tolerance.