Aje. Bettany et al., STABILITY OF TRANSGENE EXPRESSION DURING VEGETATIVE PROPAGATION OF PROTOPLAST-DERIVED TALL FESCUE (FESTUCA-ARUNDINACEA SCHREB.) PLANTS, Journal of Experimental Botany, 49(328), 1998, pp. 1797-1804
The expression of a beta-glucuronidase (GUS) transgene, under the cont
rol of the rice actin1 promoter and first intron, introduced via PEG-m
ediated transformation of protoplasts, has been followed through a num
ber of generations of vegetative propagation (tillering) in the forage
grass Festuca arundinacea. Gene expression was found to be particular
ly unstable during early generations of tillering, but more stable in
the fourth or fifth tiller generation. Loss of transgene expression wa
s not due to deletion of the transgene nor was it due to gross rearran
gements in the transgene as demonstrated by Southern blot analysis of
expressing and non-expressing tillers. Loss of transgene expression du
e to hypermethylation of the transgene promoter has been shown previou
sly, but in this case it was not possible to detect differences in the
methylation patterns of the coding and promoter regions of expressing
and non-expressing tillers. The implications for screening of transge
nic plants intended to be vegetatively propagated are discussed.