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Chloroplast-associated molecular patterns as concept for fine-tuned operational retrograde signalling
Dilek Unal1,2, Pedro García-Caparrós1,3, Vijay Kumar1
1Biochemistry and Physiology of Plants, Bielefeld University, 33501 Bielefeld, Germany.
Summary
Chloroplasts communicate with the nucleus via retrograde signaling, using molecules like reactive oxygen species (ROS). This review proposes
Area of Science:
- Plant cell biology
- Molecular plant physiology
- Organelle communication
Background:
- Chloroplasts are vital organelles, comprising 25% of mesophyll cell volume and 60% of cell protein.
- Photosynthetic carbon assimilation is the primary metabolism in illuminated leaves, requiring precise regulation.
- Intensive bidirectional information transfer (anterograde and retrograde signaling) occurs between the nucleus and chloroplasts to optimize organelle function.
Purpose of the Study:
- To review redox- and reactive oxygen species (ROS)-related retrograde signaling pathways from chloroplasts.
- To propose a new conceptual framework for understanding chloroplast-extranuclear communication.
- To highlight the role of chloroplasts in regulating nuclear gene expression and cellular processes.
Main Methods:
- Literature review and synthesis of recent research on retrograde signaling.
- Analysis of metabolite transfer pathways involved in inter-organelle communication.
- Conceptual development of the 'chloroplast-associated molecular pattern' (CAMP) hypothesis.
Main Results:
- Multiple retrograde pathways identified, utilizing metabolites from lipids, carotenoids, carbon, sulfur, nitrogen metabolism, antioxidants, and hormone precursors.
- Reactive oxygen species (ROS) play a significant role in mediating chloroplast-to-nucleus signals.
- Chloroplast performance is linked to extrachloroplast processes, including nuclear gene transcription and translation.
Conclusions:
- Retrograde signaling is crucial for optimizing chloroplast function and resource allocation.
- The proposed 'chloroplast-associated molecular pattern' (CAMP) provides a novel framework for understanding how chloroplasts influence nuclear processes.
- Understanding these signaling pathways is essential for deciphering plant responses to environmental cues and metabolic status.
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