Agrobacterium-mediated co-transformation of a pea β-1,3-glucanase and chitinase genes in potato (Solanum tuberosum L. c.v. Russet Burbank) using a single selectable marker

A pea chitinase and beta-1,3-glucanase genes in two independent plasmids (pChit and pGlu) multiplied in separate Agrobacterium tumefaciens (LBA4404) clones, were simultaneously introduced into internode explants of in vitro grown potato (Solanum tuberosum L. c.v. Russet Burbank). Both pChit and pGlu contained a neomycin phosphotransferase gene (NPT II) as the selectable marker to identify the transformants. The insertions of the transgenes were verified by the polymerase chain reaction (PCR). The transformation frequency of chitinase was 3.9% per internode and of beta-1,3-glucanase was 3.7% per internode. The cotransformation frequency of both genes was 1.6% per internode or 24% of total transformants. This frequency of co-transformation is much higher than the calculated 0.1% per internode expected using the product of the independent transformation frequencies. Northern blot analysis confirmed the expressions of both genes. The sizes of both mRNAs were approximately 1.4 kb indicating that the 1.1 kbp intron in the beta-1,3-glucanase gene was spliced out. The results indicated that the transgenic potato was able to express the intron-less chitinase and the intron-containing pea beta-1,3-glucanase genes to produce the corresponding mRNAs. This study demonstrated that it is possible to obtain an efficient co-transformation frequency in potatoes using the NPT II gene as the only selection marker. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.