Researchers at the Karlsruhe Institute of Technology (KIT) have found out how plant cells respond to stress. If their energy supply is disrupted by heat, drought, or saline soils, chloroplasts – the cells’ powerhouses – send an intracellular distress signal by forming tiny, finger-like projections. This signal specifically activates protection programs, which help to limit damage. The results of the study clearly show for the first time what the function of these previously mysterious structures is, and present an approach for making crops more resilient to climate stress.


Each plant cell contains chloroplasts, which work like little solar power stations. The tiny structures are the green energy centers of the plant cells. Absorbing the sunlight and extracting carbon dioxide from the air, they produce sugar – the energy source every plant needs for growth and survival. Without these “solar power stations,” plants would not be able to produce energy and thus could not serve as a food resource for other living beings. Another effect would be that less oxygen would be released into the atmosphere.


Protection against Heat, Drought, or Salt

If plants are under stress, for example caused by a lack of water or by high temperatures, such as those Germany and Central Europe are currently experiencing, or due to saline soils, this delicate energy system gets out of balance. Aggressive substances develop that can affect and damage important parts of the cell. To survive, the plant needs to respond quickly and activate protective measures.


In this stress situation, chloroplasts react by forming the “fingers” that were recently investigated. The researchers revealed that these structures send a signal to the central control of the cell. “Particular genes are enabled or disabled, which triggers protection programs that support the damaged areas,” said Professor Peter Nick from KIT’s Botanical Institute.


Function of a Long-overlooked Structure Deciphered

The structures were described more than 130 years ago by Gottlieb Haberlandt, a plant physiologist who taught in Berlin, but fell into oblivion, and were only rediscovered in the 1990s by US researchers. “Back then, researchers thought that these ‘stromules’ connected various solar power stations in the cell. Our results now show that their most important function is not the exchange of substances, but the forwarding of intracellular information,” explained Nick.


Approach for More Climate-resistant Crops

This discovery is particularly relevant in view of the climate crisis that puts the plants more and more often under stress. “We show that this alarm mechanism can be influenced in a targeted way. We have identified molecular factors that speed up the formation of the ‘fingers’ and make them more efficient,” said Nick. In the long run, new opportunities for farming will arise that focus on identifying wild plant varieties that can handle stress particularly well. “Maybe these properties can be transferred to crops in the future to better protect them against heat, drought, or saline soils,” said Nick.


Original publication

Toranj Rahpeyma, Javier García Varo, Fabio Mühlberg, Peter Nick: Fingers for Signaling? A Possible Role of Stromules in Intracellular Communication. Plant Physiology, 2026. DOI: 10.1093/plphys/kiag373


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