A group of transgenic barley plants expressing the bar selectable
marker gene did not produce viable offspring.
Barley (Hordeum vulgare).
bar gene from Streptomyces hygroscopicus, which produces the
enzyme PAT. The PAT enzyme inactivates the herbicide phosphinothricin,
also known as glufosinate. bar gene expression was controlled by
the maize ubiquitin promoter.
Goal of This Study:
As part of an effort to map genes in barley, twenty transgenic Golden Promise
barley lines containing the bar gene in unique locations (GP-bar)
were crossed with Oregon Wolfe Barley Dominant (OWBD) stock.
Results of This Study:
Even though none of the transgenic Golden Promise lines exhibited
morphological abnormalities, only 4 of the 20 OWBD x GP-bar crosses
produced viable seed. Progeny from the other 4 crosses showed moderate
to severe reductions in growth rate, turned yellow, and eventually died
before setting seed.
Further crosses showed that GP-bar lines with low levels of the enzyme
PAT could produce viable offspring with OWBD lines.
Genetic mapping identified a single locus on the long arm of barley
chromosome 6 as responsible for the sensitivity of the OWBD population to
high levels of PAT expression.
The researchers comment that their results may serve to "remind us of the
complex and sometimes surprising aspects of higher plant genomes" (p. 386).
Bregitzer, P., L. D. Cooper, P. M. Hayes, P. G. Lemaux et al. (2007).
"Viability and bar Expression are Negatively Correlated in Oregon
Wolfe Barley Dominant Hybrids," Plant Biotechnology Journal vol. 5,
USDA Agricultural Research Service, Abderdeen, Idaho; Oregon State
University; University of California, Berkeley.
USDA Agricultural Research Service; National Science Foundation.
Not on the market as of 2009.
Copyright 2009 The Nature