The Transformation Of Tabacco MnSOD Gene Into Baoding Alfalfa

Bio-engineering technologies are now routinly used for the genetic improvement of Medicao sativa L. However, most breeding lines of alfalfa are not easily amenable to genetic transformation and therefore can not benefit from the biotechnologies that have been developed for genetic manipulations. This paper describes a strategy that has developed to transfer the cDNA of tobacco MnSOD gene into the commercially important breeding line - Baoding alfalfa via Agrobacterium infection. Transgenic alfalfa plants have been generated that overproduce a Nicotiana plumbaginifolia L. manganese superoxide dismutase (MnSOD).The results domenstrated that baoding alfalfa is an important breeding line which easily amenable to genetic transformation. To target this mitochondrial enzyme into chloroplast, the cDNA sequence of MnSOD was fused to a chloroplast transit peptide from a pea Rubisco small subunit gene,whereas expression of the chimeric gene was driven by the CaMV 35S promoter. Putative transgenic plants were screened by NPTII -specific and MnSOD-specific PCR amplification and southern blotting, 84% of the transgenic plants gave positive results.The results of MnSOD activities demonstrated that tobacco MnSOD gene contributed to more than 50% of the total MnSOD activity in some transgenic alfalfa.