Nitrogen fertilizer helps increase crop yields, but excessive use causes
environmental pollution. Large amounts of nitrogen can also delay flowering
in rice. A recent study identified a rice nitrate transporter (NRT) that can
help increase grain yield and accelerate flowering if overexpressed.
In the rice plant, different NRTs move nitrogen from the soil into the roots
and move nitrogen compounds throughout the plant. Some NRTs sense nitrogen
levels and trigger responses. A study showed that rice OsNRT1.1A can affect
both nitrogen use and flowering time and mutant lines lacking this
transporter showed decreased use of nitrate and ammonium.
To improve yield and flowering time, the researchers created rice lines that
produced extra OsNRT1.1A. The OsNRT1.1A-overexpressing plants grew taller,
were greener, and produced more biomass, compared with regular rice grown on
the same amount of nitrogen. These plants also pulled more nitrate and
ammonium out of the medium in hydroponics experiments. In multi-year field
trials, the OsNRT1.1A-overexpressing plants showed improved yields of more
than 30% (and up to 60%) in fields with high and low levels of nitrogen
fertilization. These plants also flowered one to two weeks earlier than the
control rice plants.