Factors influencing gene expression and T-DNA transfer in A. tumefaciens-mediated transformation of rice
1997
Aldemita, R.R. | Hodges, T.K. (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 A. 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 promoter of mannopine synthetase and a truncated cauliflower mosaic virus 35S 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 A 1.36 were transformed with the derivatives of the binary vector and transformed colonies were tested for infectivity on coleoptile 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 A+656. Possible reasons for the A. tumefaciens strains with the binary vector, the border sequences, and the Ti-plasmic present, important in resistance breeding and development of strategies for geographical deployment
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