Plants are under constant stress due to pathogens, heat, or other environmental factors. Proteins can become damaged as a result and cell function is thrown off balance. Researchers at Ruhr University Bochum working with Professor Şuayb Üstün have discovered how plant cells respond to this protein stress and selectively adjust their internal processes. The researchers show that cells under stress prioritize the breaking down of damaged proteins over energy production through photosynthesis. Their findings, published in Molecular Cell, could help make plants more robust.
Thousands of proteins have to be correctly produced, folded, and regulated in each cell. Under stress conditions, this balance (known as proteostasis) becomes unstable. Misfolded or damaged proteins accumulate and can harm the cell. In order to counteract this, cells use a sort of molecular recycling system called a proteasome to break down the defective proteins. However, it was previously unclear how cells adapt this activity to different stress situations within the cell.
A control center in the endoplasmic reticulum
The researchers demonstrated that two central regulators control this adjustment: transcription factors NAC53 and NAC78. These are found in the endoplasmic reticulum (ER), an important hub of protein production. "We discovered that these factors act like a control panel," explains Gautier Langin, first author of the study. "They integrate stress signals from different areas of the cell and decide how the cell will respond."
Under normal conditions, NAC53 and NAC78 are quickly broken down. When the cell is under stress, however, they are activated, migrate to the nucleus, and activate genes that strengthen the breakdown of proteins.
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