Factors influencing gene expression and T-DNA transfer in Agrobacterium tumefaciens-mediated transformation of rice
1996
Aldemita, R.R. (Philippine Rice Research Inst., Maligaya, Munoz, Nueva Ecija 3119 (Philippines))
Rice has been routinely transformed using the direct-DNA uptake methods. Recent developments in rice genetic transformation using Agro-bacterium tumefaciens as a natural vector necessitate the investigation of factors that will promote optimum gene expression and T-DNA transfer in the recalcitrant indica rice varieties. Activities of three different promoters were investigated for transient expression using gusA after particle bombardment of suspension cells. Actin and ubiquitin promoters were found to induce higher GUS activity compared to the chimeric promoters of mannopine synthethase and a truncated cauliflower mosaic virus 35 S in the positive check. A binary vector pCGN1558 was modified to contain these promoters in front of the gusA-intron. A. tumefaciens strain EHA101 and A136 were transformed with the derivatives of the binary vector and tranformed colonies were tested for infectivity on coleptile bases of IR54 and IR72 seedlings. GUS activity of the infected coleoptile bases showed that the A. tumefaciens colonies were comparable to but not better than the positive control At656. Possible reasons for the obtained results were explained with emphasis on the importance of the compatibility of the A. tumefaciens strains with the binary vector, the border sequences, and the Ti-plasmid present
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