Circadian rhythms are finely balanced, intrinsic biological clocks that regulate a wide range of physiological processes and enable all organisms to synchronize biological processes with the environment and the predictable 24-hour cycle of day and night. In plants and algae, for instance, circadian rhythms play a crucial role in the modulation of growth and development, flowering time, metabolism and nutrient uptake. These endogenous clocks are governed by complex molecular mechanisms, involving multiple and specialized photoreceptors, and transcriptional, post-transcriptional, translational and post-translational regulation. Recent advances in multi-omics and molecular biology approaches have allowed researchers to delve deeper into the role of circadian clocks in different plant species and (micro)algae, including non-model plant and algal species. Investigating how circadian rhythms function in photosynthetic organisms is fundamentally relevant and timely, for instance, to understand how they affect plant physiology and ecology, while also holding clear potential for agriculture and biotechnology. Novel insights into circadian clock regulation can indeed help in discovering new approaches for bioengineering the plant/algal circadian clocks e.g. to increase photosynthetic efficiency, resource utilization and crop yield, or enhance resilience to environmental stressors.

In support of the United Nations’ Sustainable Development Goal 2 (SDG 2: Zero Hunger) and 13 (SDG 13: Climate Action), BMC Plant Biology presents the collection Circadian rhythms in plants and algae. This Collection invites research on circadian rhythms and their mechanisms of regulation in photosynthetic organisms. Research on circadian clocks with implications for sustainable agriculture, crop/algal improvement, and potential biotechnological applications will also be considered. We invite submissions of research articles that explore, but are not limited to, the following topics:

• Mechanisms and regulation of circadian rhythms in plants and algae, including studies conducted on non-model plant and algal species
• Regulation of plant/algal circadian rhythms by photoreceptors (e.g. cryptochromes and phytochromes)
• Transcriptional, post-transcriptional, translational and post-translational regulation of circadian rhythms in plants and algae
• The role and impact of circadian rhythms on photosynthesis
• The role and impact of circadian rhythms on metabolism in plants and algae
• Circadian regulation of plant development, flowering, senescence and other photoperiodic processes
• Adaptation of circadian clocks to abiotic and biotic stress, and environmental changes, in plants and algae
• Epigenetic regulation of circadian rhythms in plants and algae
• Regulation of plant immunity and defense response by circadian rhythms
• Regulation of abiotic stress responses by circadian rhythms
• Evolution of circadian rhythms in photosynthetic organisms
• Biotechnological applications and bioengineering of circadian rhythms for crop and algal improvement (e.g. yield, metabolism, stress resilience)
• Integrative multi-omics approaches to study circadian rhythms in plants and algae, including field studies and large-scale time-series
• Modelling approaches to study circadian rhythms and predict gene expression profiles in complex field conditions

All manuscripts submitted to this journal, including those submitted to collections and special issues, are assessed in line with our editorial policies and the journal’s peer-review process. Reviewers and editors are required to declare competing interests and can be excluded from the peer review process if a competing interest exists.

Carbon metabolism is central to the growth, development and productivity of photosynthetic organisms. It involves dynamic regulation and interplay between a number of complex processes (e.g. photosynthesis, carbon use and storage, respiration, nutrient metabolism), response and adaptation to environmental cues and stress (e.g. light, CO₂ content, temperature), as well as the integration of fine-tuned enzymatic activity, post-translational modifications and signalling pathways.

Over the past decades, much research has been carried out to understand carbon fixation and utilization in model plants/crops, as well as other photosynthetic organisms. Advancing our understanding of the working principles and regulation of key enzymes like Rubisco, the Calvin–Benson–Bassham (CBB) cycle, C3, C4, and CAM metabolism, carbon concentrating mechanisms (CCMs), or how specific micro-compartments and organelles facilitate carbon concentration, has fundamental relevance. Moreover, the engineering of carbon metabolism has the potential to help addressing current global challenges linked to food security and climate change. For instance, novel insights into carbon metabolism regulation can inform breeding strategies to enhance crop yield and resilience by optimizing photosynthetic efficiency and carbon utilization, and lead to metabolic engineering of photosynthetic (micro)organisms with improved carbon fixation.

In support of the United Nations' Sustainable Development Goal 2 (SDG 2: Zero Hunger), BMC Plant Biology launches the Collection Plant carbon metabolism. This Collection invites research addressing the mechanisms and regulation of plant carbon metabolism, including research that explores new applications and approaches to modulate carbon metabolism and enhance the yield and stress resilience in crops and photosynthetic organisms (e.g. micro/macroalgae, cyanobacteria). We invite researchers and experts in the field to submit research articles that explore, but are not limited to, the following topics:

• C3, C4 and CAM metabolism in photosynthetic organisms: diversity, regulation and evolution
• Mechanisms and regulation of the Calvin-Benson-Bassham (CBB) cycle in photosynthetic organisms
• Synthesis, assembly, mechanisms and activity regulation of Rubisco
• Functions and diversity of carbon-concentrating mechanisms (CCMs) in photosynthetic organisms
• Functions, working principles and diversity of micro-compartments and organelles that facilitate carbon concentration in photosynthetic organisms (e.g. carboxysome, pyrenoid)
• Mechanisms and regulation of carbon allocation (e.g. starch and sucrose metabolism)
• Mechanisms and regulation of the central carbon metabolism, e.g. glycolysis, Oxidative Pentose Phosphate pathway, the Tricarboxylic Acid (TCA) cycle in photosynthetic organisms
• Metabolic engineering of carbon metabolism to enhance yield and stress resilience in photosynthetic organisms
• Synthetic biology approaches to enhance carbon fixation
• Impact of environmental stress on carbon metabolism
• Regulation of plant carbon assimilation metabolism by post-translational modifications
• Role of plant secondary metabolites in carbon metabolism regulation

All manuscripts submitted to this journal, including those submitted to collections and special issues, are assessed in line with our editorial policies and the journal’s peer-review process. Reviewers and editors are required to declare competing interests and can be excluded from the peer review process if a competing interest exists.