Enzyme research may lead to flood resistance

Scientists discover that manipulating plant cysteine oxidases may help enhance crops’ flood-resistance capabilities

The recent discovery of the molecular structure of plant enzymes that control a plant’s response to lower oxygen levels could to lead to ways to manipulate the enzyme function and produce flood-resistant crops.

The research was conducted at the University of Sydney in Australia and the University of Oxford in the United Kingdom.

Crops such as wheat, barley and rice are able to survive temporary periods of flooding by activating energy pathways that do not rely on air when floodwater creates low oxygen conditions. These energy responses are controlled by oxygen-sensing enzymes called plant cysteine oxidases (PCOs), which use oxygen to regulate the stability of proteins that control gene activity.

The study focused on the structures of two PCOs from arabidopsis, a popular plant used in laboratory experiments.

“The plant cysteine oxidases — the enzymes studied in our work — provide a direct link between oxygen availability and the molecular mechanisms underpinning flood responses in plants,” said Mark White with the School of Chemistry at the University of Sydney. “This suggests that their manipulation might provide an effective and sensitive intervention point to improve crop flood tolerance.”

Certain enzymes in plants are oxygen sensing and certain plant species may be better equipped than others with this feature.

The PCOs and their associated proteins are only present in higher plants, including many important crop species such as wheat, barley and soybeans, said White.

He said that the PCOs regulate the stability of proteins responsible for upregulating genes linked to low oxygen responses like those associated with anaerobic metabolism. This results in reducing the plant’s oxygen consumption until the supply of air is increased.

The proteins regulate genes (turn them on and off) to make sure they are expressed in the right cell at the right time in the right amount. The PCOs regulate those proteins responsible for genes linked to low oxygen.

Manipulating the PCOs to enhance crop flood-resistance capabilities might be approached in two ways.

“There are two possible approaches which could be adopted; genetic and chemical,” said White. “Genetics will allow subtle, well-defined changes in the composition of the PCO sequence to be introduced to a crop following successful initial experiments with the isolated enzyme. Here, the change will be inherent.

“Chemical would involve designing small molecules that can interact with the PCOs and change their activity. In this scenario, the compound could be sprayed on a crop, much like a pesticide, to prime it for a flood event, increasing its chance of recovery after water submergence.

“Both can be assisted by our work, but the former is probably more accessible in the near future and will probably be more sustainable long term. Many more experiments are needed before either approach can be verified as a viable strategy.”

The research was published recently in the journal Proceedings of the National Academy of Sciences.

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