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June 13, 2008
Source:
CropBiotech Update
Nitrogen is a major limiting
factor in plant productivity. Crop plants, especially those
grown for grain yield, are usually supplied with inorganic
nitrogen fertilizers. The use of nitrogen fertilizer, however,
is generally inefficient. It is estimated that only about a
third of the fertilizer applied is actually absorbed by crops.
Unused fertilizer can leach into ground water or be washed away
into lakes, rivers and streams, where it depletes the bodies’
dissolved oxygen and induces phytoplankton bloom. Thus,
development of plants that can take-up and assimilate nitrogen
efficiently has been a long-term goal of agricultural
researchers.
Scientists from the University
of Alberta in Canada have developed nitrogen use efficient
(NUE) transgenic rice lines. The NUE rice harbors alaAT gene
(codes for the enzyme alanine aminotransferase) from barley
driven by a rice tissue-specific promoter. The transgenic plants
exhibited higher biomass and grain yield compared to its non-GM
counterparts. The GM lines also demonstrated significant changes
in key metabolites and total nitrogen content, indicating
increased nitrogen uptake efficiency.
Read the paper at
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1467-7652.2008.00351.x
Genetic engineering of improved nitrogen use
efficiency in rice by the tissue-specific expression
of alanine aminotransferase
Ashok K. Shrawat, Rebecka T. Carroll, Mary
DePauw, Gregory J. Taylor and Allen G. Good |
| SUMMARY
Nitrogen is
quantitatively the most essential nutrient for
plants and a major factor limiting crop
productivity. One of the critical steps limiting the
efficient use of nitrogen is the ability of plants
to acquire it from applied fertilizer. Therefore,
the development of crop plants that absorb and use
nitrogen more efficiently has been a long-term goal
of agricultural research. In an attempt to develop
nitrogen-efficient plants, rice (Oryza sativa L.)
was genetically engineered by introducing a barley
AlaAT (alanine aminotransferase) cDNA driven by a
rice tissue-specific promoter (OsAnt1). This
modification increased the biomass and grain yield
significantly in comparison with control plants when
plants were well supplied with nitrogen. Compared
with controls, transgenic rice plants also
demonstrated significant changes in key metabolites
and total nitrogen content, indicating increased
nitrogen uptake efficiency. The development of crop
plants that take up and assimilate nitrogen more
efficiently would not only improve the use of
nitrogen fertilizers, resulting in lower production
costs, but would also have significant environmental
benefits. These results are discussed in terms of
their relevance to the development of strategies to
engineer enhanced nitrogen use efficiency in crop
plants. |
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