Photosynthetic organisms constantly perceive changes in nutrient availability, and the ratio of carbon (C) and nitrogen (N) plays a crucial signaling role in their metabolism, growth, and development. Under environmental stress, the delicate equilibrium in the C/N balance is disrupted, leading to an increase in reactive oxygen species (ROS) and reactive nitrogen species (RNS), which in turn affects energy homeostasis. The redox status also controls N metabolism, making accurate sensing and signaling of the C/N ratio and reactive molecule levels essential for cellular homeostasis and survival. Despite the identification of central hubs like TOR and SnRK1 kinases and the HY5 transcription factor, significant gaps remain in understanding the complex network of interconnected regulations that ensure global equilibrium. Further research is needed to resolve the intricate relationship between C and N metabolism and redox homeostasis in photosynthetic organisms.

This research topic aims to gain insight into the importance of C and N metabolism and balance sensing during stress responses in photosynthetic organisms and its transduction to key integrators that maintain energy homeostasis. Addressing the role of subcellular locations and tissue- and organ-specific expression of C/N sensors and transducers under stress is crucial. Additionally, the topic seeks to clarify contradictory data in the literature and explore the roles of retrograde signaling. Understanding these molecular mechanisms and their dynamic regulation will improve biomass yield and stress resistance through new technologies like CRISPR-Cas9.

To gather further insights into the complex interplay between C/N balance, ROS status, and energy homeostasis under abiotic stress, we welcome articles addressing, but not limited to, the following themes:
- Sugar and nitrogen sensing under environmental stress
- Rapid readjustment of gene expression and metabolism in stressful conditions
- Adjustment of C/N balance in the plant stress response
- Role of ROS and RNS and cellular redox state under unfavorable conditions
- The interplay between metabolism and selective organelle autophagy under stress
- Importance of subcellular localization, tissue-organ, and developmental stage-specific expression of C/N sensors/transducers, key transporters, and transcription factors
- Role of key kinases TOR and SnRK in regulating cellular homeostasis and growth under unfavorable conditions
- Importance of PII protein under environmental stress
- Description of new proteins or mechanisms involved in C/N homeostasis and energy management
- New technologies of genome editing to improve nitrogen use efficiency (NUE), such as CRISPR-Cas9

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C/N Balance and Redox Homeostasis in Photosynthetic Organisms Under Stress