Crops tricked to take up more phosphate

Australian researchers have overcome a critical hurdle in boosting plant performance with limited fertilisation.

If translated to crop plants, the findings could save Australian farmers $300 million per year and reduce run-off phosphorous in waterways by 20 per cent.

The results, published in American journal Plant Physiology, describe how manipulating gene networks to ‘trick’ plants into thinking phosphate is scarce, leads them to use this essential nutrient more efficiently, by up to 50 per cent.

The team of researchers at the ARC Centre for Excellence in Plant Energy Biology and the Centre for AgriBioscience at La Trobe University, have boosted plant performance under limited phosphate by targeting genes that regulate phosphate transport in plant roots, resulting in increased phosphate uptake while sidestepping negative effects on plant growth and yield.

The approach overcomes a hurdle encountered by previous attempts to increase plant phosphate uptake, where reduced growth and yield were observed as a result of plants not being able to process the extra phosphate.

The team is now collaborating with researchers at China’s Zhejiang University to apply their findings to rice plants. The discovery would be even more valuable in China where overuse of fertilisers is a huge environmental and economic issue. There is also great interest in the United States where the findings were published.

Phosphate, an essential nutrient for plant growth, is a limited and non-renewable resource, with high-grade phosphate reserves gradually being exhausted. According to the United Nations, global food production will need to double by 2050. Improving fertiliser use by crops, in particular phosphorus use, is essential for sustainable agriculture.

In the field, only a small percentage of the applied phosphate fertiliser is taken up by plants, with the rest remaining in the soil or being lost as fertiliser run-off and ending up in waterways. Increasing phosphate uptake by plants will result in less fertiliser wastage and, ultimately, a need to apply less of this limited resource for plant growth.

“Our approach is focused on altering phosphate uptake and transport by roots, to avoid negative impacts on shoot metabolism,” said senior researcher Dr Ricarda Jost.

“Our study showed that a reduction in plant vigour can be overcome by a targeted approach. By manipulating local gene networks, plants can be ‘tricked’ into thinking that phosphate is scarce which puts them into a heightened state of alert. As a result, they will launch a number of responses that lead to higher phosphate uptake by roots.”

The researchers took a data-mining approach to predict genes that respond to changes in phosphate supply in a root-cell specific manner. By targeting local regulators of phosphate transport in root cells, the researchers found they achieved a better overall outcome for plant performance.

The study’s first author, Joshua Linn, said: “We focused on genes in the cells of plant roots that are known to control nutrient flux.

“We were delighted that plants with reduced expression of these genes grew much better than the controls when they were exposed to lower phosphate levels.”

The plants took up more phosphate, but were also better equipped to metabolically convert that phosphate in order to promote growth.

Professor Jim Whelan, who led the study, said: “Crops that lacked these negative regulators would require fewer fertiliser applications due to more efficient nutrient acquisition, reducing fertiliser run-off and water pollution. A win-win for farmers’ budgets and the environment.”

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