A study published in the journal Molecular Plant reports that a new
bioengineering approach for boosting photosynthesis in rice plants could
increase grain yield by up to 27%. Called GOC bypass, the approach enriches
plant cells with CO2 that would otherwise be lost through photorespiration.
The genetic engineered plants were greener and larger and showed increased
photosynthetic efficiency and productivity under field conditions, with
particular advantages in bright light.



The main genetic approach in increasing the yield potential of major crops
focuses on photosynthesis. One way to increase photosynthesis is to bypass
photorespiration, a light-dependent process in which oxygen is taken up and
CO2 is released. Several studies conducted in the past introduced
photorespiratory bypasses into plants, but most of the experiments were
carried out using Arabidopsis. In the new study, the research team developed
a strategy to essentially divert CO2 from photorespiration to
photosynthesis. They converted a molecule called glycolate, a product of
photorespiration, to CO2 using three rice enzymes: glycolate oxidase,
oxalate oxidase, and catalase. To deploy GOC bypass, which was named for the
three enzymes, the researchers introduced Genes encoding the enzymes into
rice chloroplasts.

The results showed that the photorespiratory rate was suppressed by 18%-31%
compared to normal, and the net photosynthetic rate increased by 15%-22%,
primarily due to higher concentrations of cellular CO2 used for
photosynthesis. Compared to plants that were not genetically engineered, the
GOC plants were consistently greener and larger, with an above-ground dry
weight that was 14%-35% higher. Moreover, starch grains grew in size by 100%
and increased in number per cell by 37%. In the spring seeding season, grain
yield improved by 7% to 27%.

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