Transgene integration complexity and expression stability following biolistic or Agrobacterium-mediated transformation of sugarcane

Sugarcane (Saccharum spp. hybrids) accounts for 80% of the table sugar produced worldwide and is also a prime feedstock for biofuel production. However, very few studies are available for directly comparing Agrobacterium tumefaciens-mediated transfer of T-DNA (AMT) and biolistic transfer of minimal expression cassettes (BLT MC) regarding transgene complexity and expression stability. In this study, the transformation efficiency, transgene integration pattern, expression level, and expression stability were compared in the commercially important sugarcane cultivar CP88-1762. A total of 312 transgenic lines derived from AMT and 250 lines derived from BLT MC were identified by PCR from genomic DNA using nptII-specific primers. Lines were analyzed with both qPCR (TaqMan®) and NPTII ELISA to determine the nptII transgene copy number and expression level. The results of Southern blot analysis on selected lines were highly correlated to the qPCR results. There were no significant differences between the two transformation systems for transformation efficiency, frequency of single copy integration, or level and stability of transgene expression when carried out with the same expression cassette, tissue culture, and selection procedure in 12 independent experiments. These findings suggested that both BLT MC and AMT provide suitable platforms for generation of elite sugarcane events.