Abstract |
Herbicides count almost a century of life and still the mode of action for many of them in not completely understood.
Acetyl CoA carboxylase has been used as target of herbicides for many years and the last fifteen years
has also become an insecticide target. ACCase catalyzes the first committed step of fatty acid biosynthesis and
two distinct forms of the enzyme are found in nature. The eukaryotic form which is found in the cytosol of plant,
insect and mammalian cells and the prokaryotic one which is found in bacteria. In most of the plants both forms
are present, the former in the cytosol and the latter in chloroplasts, except from grasses that express only the eukaryotic
form, on both cytoplasm and chloroplasts. Chloroplasts are responsible for the 80% of the total enzymatic
activity in leaves and as the inhibitors of ACCase block exclusively the eukaryotic form, this class of herbicides
shows great potency against grass ACCase activity. Single point mutations in chloroplastic ACCase have been associated
with herbicide resistance in many grass species. In a recent study, a single point mutation, the substitution
of an alanine residue with a valine residue, in a conserved region of the CT domain of ACCase, was found
in Bemicia tabaci. The mutation was associated with insecticide resistance and herbicide susceptibility. Plants
normally have a valine residue in the same position and a great question is born: “what are the tolerant levels to
pesticides in plants with the reverse mutation”, the substitution of the valine with an alanine.
Oryza sativa belongs to grass family and that provides it with all the specifications needed for this study. Moreover,
rice is one of the most economically important crops and the last years, herbicide resistant cultivated rice varieties
have been a breakthrough technology and has solved severe weedy rice infestation. Furthermore, rice has already
been distinguished as a monocot crop model system, consequently, robust inventions and new biotechnological
tools, like selection markers, are imperative. In this study Oryza sativa will be used for genetic modification in
order to express a mutated form (V2086A) of the chloroplastic ACCase in order to check the tolerant levels to pesticides
and the possible biotechnological applications.
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