Therefore, we attempted to elucidate the mechanism of high transformation frequency in CAG18439 as follows (Table 7 and Figs. 3 6).
These results suggest that unidentified mutation(s) in the CAG18439 chromosome other than Tn10 and lacI cause the high transformation frequency in CAG18439.
In high-frequency combinations, it was observed that CAG18439 caused high transformation frequency not only as the recipient cell but also as the donor cell (Tables 2 and 3).
If deletion of an ACS resulted in loss of the high transformation frequency of the ARS, the ACS was denoted as functional.
In the present investigation, we have been able to successfully introduce marker genes into bread wheat and durum wheat with a high transformation frequency.
The high transformation frequency, together with the precision and simplicity of T-DNA, make A. tumefaciens-mediated transformation a suitable genome mutagenesis approach in filamentous fungi, such as Trichoderma, Aspergillus, Beauveria and Metarhizium [ 22, 27, 32, 33].
These growth characteristics and the high transformation frequency of A. rhizogenes have made the production of 'composite plants' in vitro and ex vitro a tool to test gene functions for root biology [ 8- 10].
We could not accurately assess the BIR frequency of the pif1 -m2 mutant using the plasmid-based assay due to more efficient telomere healing at the telomere-seed sequence of the linear CFV leading to an artificially high transformation frequency (data not shown) (Schulz and Zakian 1994).
The high transformation frequency, together with the precision and simplicity of T-DNA integration, makes T-DNA a suitable element for genome mutagenesis approaches in white-rot fungi such as gene tagging, promoter entrapment and gene activation, which can also be exploited in different biotechnological applications [ 11, 14].
In general, higher transformation frequencies were observed in E. coli O157 H7 9×1022 to 1.25×104 transformants/µg) than in Salmonella (1.2×102 to 1.4×103 transformants/µg).
