U. NOTTINGHAM (UK) — Discovery of the mechanism by which plants sense low oxygen levels could eventually lead to the production of high-yielding, flood-tolerant crops.
The mechanism, reported in the journal Nature, controls key proteins in plants that cause them to be unstable when oxygen levels are normal. When roots or shoots are flooded and oxygen levels drop, the proteins stabilize.
“We have identified the mechanism through which reduced oxygen levels are sensed. The mechanism controls key regulatory proteins called transcription factors that can turn other genes on and off,” says Michael Holdsworth, professor of crop science at the University of Nottingham.
“It is the unusual structure of these proteins that destines them for destruction under normal oxygen levels, but when oxygen levels decline, they become stable.
“Their stability results in changes in gene expression and metabolism that enhance survival in the low oxygen conditions brought on by flooding. When the plants return to normal oxygen levels, the proteins are again degraded, providing a feedback control mechanism.”
Holdsworth and colleague Julia Bailey-Serres, professor of genetics at the University of California, Riverside, expect that the findings will make it possible over the next decade to manipulate the protein turnover mechanism in a wide range of crops prone to damage by flooding.
As Pakistan, Bangladesh, Vietnam, Australia, the UK, and US have all faced catastrophic flooding in recent years, tolerance of crops to partial or complete submergence is a key target for global food security. Because they are starved for oxygen, crops are unable to survive a flood for long periods of time, leading to drastic reductions in yields for farmers.
“At this time, we do not know for sure the level of conservation across plants of the turnover mechanism in response to flooding. We have quite a bit of assurance from our preliminary studies, however, that there is cross-species conservation,” says Bailey-Serres.
“Our experiments on Arabidopsis show that manipulation of the pathway affects low oxygen stress tolerance. There is no reason why these results cannot be extrapolated to other plants and crops. Still, we have many research questions to answer on the turnover mechanism. What we plan to do next is to nail down this mechanism more clearly.”
Holdsworth had the first hint of the discovery while investigating the regulation of gene expression during seed germination. He connected the mechanism of degradation of key regulatory proteins with changes in the expression of genes associated with low oxygen stress that Bailey-Serres has studied extensively.
“The puzzle pieces fell quickly into place when the expertise of the two teams was combined,” Holdsworth says.
The work was funded by the UK Biotechnology and Biological Sciences Research Council, Malaysian government through MARA, the US Department of Agriculture National Institute of Food and Agriculture, and the National Science Foundation.
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