How plants sense low oxygen levels to survive flooding

University of California, Riverside: As countries such as Pakistan, Bangladesh, Vietnam and parts of the United States and United Kingdom have fallen victim to catastrophic flooding in recent years, tolerance of crops to partial or complete submergence is a key target for global food security. Starved of oxygen, crops cannot survive a flood for long periods of time, leading to drastic reductions in yields for farmers.

Experts at the University of California, Riverside and The University of Nottingham now report they have discovered how plants sense low oxygen levels to survive flooding – a finding that could lead eventually to the production of high-yielding, flood-tolerant crops, benefiting farmers, markets and consumers everywhere.

Specifically, the researchers identified the molecular mechanism involved. This mechanism controls key plant proteins, causing them to be unstable when oxygen levels are normal. When roots or shoots are flooded and oxygen levels drop, these proteins become stable.

“When a plant cell is starved for oxygen, it cannot efficiently generate adenosine triphosphate or ATP, the high-energy molecule plants use for energy storage,” explained Julia Bailey-Serres, one of the key researchers participating in the study and a professor of genetics in the Department of Botany and Plant Sciences at UC Riverside. “Because the plant cannot generate enough energy to sustain normal growth, it tries a different approach: it taps into its energy reserves, resulting in more sugars breaking down, as opposed to when oxygen is available, in order to produce ATP. These subtle changes in metabolism are characteristic of low oxygen stress in plant and animal cells. It’s similar to the production of lactic acid in our bodies when we exercise. We produce lactic acid as a by-product because we are not producing energy aerobically.”

...“The mechanism controls key regulatory proteins called transcription factors that can turn other genes on and off,” explained Michael Holdsworth, a professor of crop science at the University of Nottingham who co-led the research project with Bailey-Serres. “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.”...

UC Riverside graduate student Seung Cho Lee (left) and his advisor Julia Bailey-Serres seen in the lab with a tray of Arabidopsis plants. Arabidopsis is a small flowering plant used widely by plant biologists as a model organism. Photo credit: UCR Strategic Communications