Genetic mutation could improve cash crop growth

A team of IU biologists led by professor David Kehoe has discovered a new protein function that might help regulate the physical and genetic expression of genes in agriculturally important crops.

The protein, called translation initiation factor 3, or IF3, could potentially allow biologists to modify physical traits of cash crops to improve plant growth and development.

It might now be possible to manipulate the expression patterns of different IF3 family members to allow them to photosynthesize light more efficiently.

The gene that encodes IF3, infC, is usually so essential to the cell that mutating it is deadly, Kehoe said.

However, this group has found a form of IF3 in a cyanobacterium that helps the plant to more efficiently absorb light for photosynthesis, Kehoe said.

This is because the protein is able to control the cyanobacterium’s genes that cause its different responses to color changes in surrounding light environment.

This process is known as chromatic acclimation.

Through chromatic acclimation, these photosynthesis genes produce red-pigmented proteins called phycoerythrin when the cells are grown in green light.

This allows them to absorb light better to drive photosynthesis.

This discovery was made unexpectedly as part of a research effort to search for mutants that incorrectly control phycoerythrin, Kehoe said.

While he and his team were looking at Fremyella diplosiphon, a cyanobacterium ideal for the study of light color responsiveness, they found two different infC genes.

One of these controlled photosynthesis gene expression and one did not.

Multiple infC genes in a single organism had never been discovered before, Kehoe said.

“The two most exciting things are discovering an IF3 protein that can have a regulatory role in plants ... and that commercially important crop species are also likely to use IF3 gene families to regulate gene expression,” Kehoe said.

Kehoe and his team named the genes IF3 alpha and IF3 beta.

However, only IF3 alpha was also able to regulate photosynthetic gene expression in addition to its original function of protein synthesis.

Surprisingly, either of these could be mutated independently without killing the cells, Kehoe said.
This means proteins in the IF3 family were encoded with some overlapping functions as well.

The biologists also found that multiple IF3 families exist in a variety of different plant species, said Kehoe, the most important of which may be agriculturally important crops.

He said this result is not surprising since plants evolved from cyanobacteria.

“The most important thing for us right now is that we need to figure out how IF3 is working to regulate gene expression,” Kehoe said.

He said the researchers then need to confirm the gene expression is occurring regularly in plants before using that information to modify plants.

“If you don’t know how something works, you can’t modify it,” Kehoe said. “That’s what the whole process of discovery is about.”

— Tori Lawhorn