How do plants protect themselves from extreme heat? An international research team led by Yasin Dagdas at the GMI – Gregor Mendel Institute of the Austrian Academy of Sciences (OeAW) has decoded an important component of the plant protection system in greater detail. The team shows that a protein called CESAR plays a central role in specifically degrading damaged proteins that form aggregates in plant cells. The study has just been published in Developmental Cell.

How plants protect themselves

Plants are constantly under stress — heat, drought, and pests, for example. Under such conditions, many proteins inside the cells become damaged. If these defective proteins accumulate, they can become dangerous, disrupt essential processes, and severely harm the cell. To prevent this, plants have a highly precise “clean-up mechanism”: selective autophagy, a process in which cellular components are tagged and degraded. Special helper proteins — so-called SARs (selective autophagy receptors) — detect which parts of the cell are damaged or unnecessary and direct them for disposal.

Scientists already know many of these SARs in animals, but plants have their own versions — some similar to those in animals, others completely different. Many plant SARs have remained unknown until now, limiting our ability to modulate selective autophagy to improve plant stress tolerance.

Tracking down the helper proteins

“In our work, we wanted to identify new receptors — and understand which processes they are involved in,” explains Marintia Mayola Nava-García, one of the researchers on the team. “Especially with climate change and the heatwaves that are already happening and will increase in the future, we want to understand how plants use selective autophagy to stay in tune with their environment and adapt to it,” she says.

The team led by Yasin Dagdas has now developed a method to detect previously hidden plant SARs. Together with the Proteomics facility at the Vienna Biocenter, they examined five plant species — including green algae, moss, and flowering plants — to determine which proteins interact with ATG8, a key protein that facilitate which proteins are destined for degradation.

But, “to find only the truly relevant proteins, we had to narrow down the huge list of possible ATG8 interaction partners,” Nava-García explains. Using a new approach, the researchers were able to identify only those proteins that bind ATG8 in a functional way. Among them, they discovered a particularly important receptor: CESAR.

From basic research to climate-resilient agriculture

“CESAR emerged as one of the strongest interaction partners in four of the five tested species — that immediately suggested it might be important,” says Nava-García. CESAR helps remove proteins that become damaged during heat stress. Plants lacking CESAR are clearly more sensitive to high temperatures. The results suggest that CESAR is a central factor helping plants maintain protein homeostasis under stressful conditions.

In the long term, these findings could help develop crop plants that are more resilient to heat and other stress conditions — an urgent goal given increasing heatwaves and climate-related harvest losses. In addition to CESAR, the researchers identified many other potential SARs, significantly expanding the SAR repertoire in plants. This resource will support researchers in understanding and mitigating the adverse effects of climate change on plant resilience.”