Using an antisense approach, Deng et al [23] have transformed Lemont rice
(indica×japonica) with the OsGST III subunit from rice in an antisense orientation.
Transgenic lines were sensitive to pretilachlor. GST activity utilizing cinnamic acid, 1-chloro-
2,4-dinitrobenzene (CDNB), and pretilachlor as substrates was reduced in transformed rice,
suggesting that the OsGST III gene plays an important role in the detoxification of the
herbicide pretilachlor and the metabolism of phenolic compounds.
Tobacco transgenic plants over-expressing a cotton GST gene, which had been shown to
have both GST and GPX (Glutathione Peroxidase) activities, developed enhanced tolerance to
methyl viologen (0.03 mmol/L) [24]. Unfortunately, no other herbicide has been tested,
while, at the same time, the authors did not mention the number of transgenic copies in their
lines, thus it is not possible to determine if the tolerance is the result of a “gene dosage”
effect.
The maize GST I isoenzyme (belonging to the theta class), shows significant catalytic
activity for the chloroacetanilide herbicide alachlor and appears to be involved in its
detoxification. The gene encoding GST I was introduced into tobacco plants. The transgenic
plants showed substantially higher tolerance to alachlor compared to non-transgenic plants in terms of root, leaf and vigorous development when grown on MS medium supplemented with
alachlor [8]. Thus, if GSTs are involved in the detoxification of herbicides, they could be of
great use in the development of a phytoremediation system for the degradation of herbicide
pollutants in agricultural fields. Tobacco plants which are susceptible to fomesafen were
transformed with a soya GST gene from the U class and with a dual construct (hGSH and
GST). Plants carrying the dual construct were significantly more tolerant to fomesafen
compared to wild-type tobacco plants, while plants carrying only hGSH did not exhibit higher
protection compared to the wild-type, suggesting that protection requires not only the GST
gene but also hGSH in order to become resistant. In contrast, wild-type tobacco was highly
susceptible to the herbicide fomesafen [25].