A secondary effect of transformation in Rhizobium leguminosarum transgenic for Bacillus thuringiensis subspecies tenebrionisδ-endotoxin (cryIIIA) genes

The release of genetically engineered micro‐organisms and viruses into the environment

“…For example, transformation has induced a change in a transgenic rhizobium, that is unrelated to the intended function. The Bacillus thuringiensis toxin transgene that was inserted to confer pest resistance of nodulated pea roots (Giddings et al, 1997) resulted in consistently greater than expected nodule occupancy in competition experiments with the non-engineered parent strain indicating that the engineered strain is better able to compete for nodule sites than the parent strain, a feature which has remained stable over 3 yr of experiments.…”

“…These could cause pleiotropic effects, or the transgene itself might cause pleiotropy in the absence of mutation (Giddings et al, 1997). The insertion of non-coding regulatory DNA could alter the timing and level of expression of native genes, perhaps turning expression of some genes on or off entirely (Tiedje et al, 1989).…”

“…Olesinski et al, 1995 ;Giddings et al, 1997). In bacterial mutants selected for novel phenotypes pleiotropy is common and is usually maladaptive, leading to reduced fitness .…”

“…Secondary effects of transformation can be caused by the random insertion of transgenes into the genome (Giddings et al, 1997) through insertion mutation or the inserted gene promoter altering the expression of native genes (Colwell et al, 1987 ;Tiedje et al, 1989). These could cause pleiotropic effects, or the transgene itself might cause pleiotropy in the absence of mutation (Giddings et al, 1997). The insertion of non-coding regulatory DNA could alter the timing and level of expression of native genes, perhaps turning expression of some genes on or off entirely (Tiedje et al, 1989).…”

“…Although the importance of pleiotropy is often considered to be negligible, recent evidence indicates that this is not always the case (e.g. Olesinski et al, 1995 ;Giddings et al, 1997). In bacterial mutants selected for novel phenotypes pleiotropy is common and is usually maladaptive, leading to reduced fitness .…”