Mitochondrial retrograde signaling: Integrating metabolic, environmental, and hormonal cues to shape plant...

Mitochondria are central regulators of energy production and cellular stress responses in plants. When mitochondrial function is impaired retrograde signaling pathways are triggered to adjust nuclear gene expression and restore cellular homeostasis. This process, known as mitochondrial retrograde regulation (MRR), integrates signals derived from reactive oxygen species, redox changes, and metabolic imbalances. In this review, we examine the major MRR pathways in plants, with emphasis on both transcriptional and post-transcriptional regulation. We explore how specific disruptions in the mitochondrial electron transport chain result in distinct nuclear responses and how these are influenced by developmental context and hormonal signaling. Recent studies have revealed interactions between mitochondria, chloroplasts, and the endoplasmic reticulum, highlighting the complexity of inter-organelle communication. Of particular interest is the coordination between mitochondrial and chloroplast signals through shared metabolic shuttles, raising questions about the autonomy of MRR in planta. We conclude by identifying current challenges, including the need to determine whether mitochondrial stress responses occur independently of chloroplast signaling or have become co-regulated over evolutionary time. Understanding these mechanisms will be essential for dissecting energy organelle coordination and developing strategies to improve stress resilience in plants.