Sweet way to greater yield

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Blue dye, in this cross-section of a maize cob, highlights the rice gene that controls T6P in the kernels’ phloem.

THREE years ago, biotechnologists demonstrated in field trials that they could increase the productivity of maize by introducing a rice gene into the plant that regulated the accumulation of sucrose in kernels and led to more kernels per maize plant.

They knew that the rice gene affected the performance of a natural chemical in maize, trehalose 6-phosphate (T6P), which influences the distribution of sucrose in the plant. But they were keen to discover more intimate details of the relationships governing the increased productivity.

“Now we know far more about how this yield effect has been achieved,” says Matthew Paul, who led the Anglo-American team from Rothamsted Research and Syngenta, a biotechnology company that also funded the work. The team’s findings are published recently in Plant Physiology.

The transgenic maize depressed levels of T6P in the phloem, a major component of the plant’s transportation network, allowing more sucrose to move to developing kernels
and, serendipitously, increasing rates of photosynthesis, thereby producing even more sucrose for more kernels.

The team also chose to target the phloem within the plant’s reproductive structures. “These structures are particularly sensitive to drought – female kernels will abort,” says
Paul, a plant biochemist at Rothamsted. “Keeping sucrose flowing within the structures prevents this abortion.”