Researchers from the University of Cambridge have discovered a new family of photosynthesis-controlling gene regulators which could impact crop development for sustainability and global food security.
The study by Natasha Yelina and Eftychios Frangedakis was published in Cell on 23 July 2024. It was led by Professor Julian Hibberd, head of the Molecular Physiology group at the Department of Plant Sciences.
The research has identified a family of transcription factors – DNA-binding proteins that turn genes on and off to control plant function – which were previously unknown to affect photosynthesis.
In plants, photosynthesis takes place in organelles known as chloroplasts. Until now, biologists knew that photosynthesis was controlled by members of the GOLDEN2-LIKE (GLK) family of transcription factors. This study shows that a new class of gene regulators, MYB (myeloblastosis)-related transcription factors, also play a role in controlling photosynthesis and chloroplast development.
These findings open-up significant opportunities to better understand critical processes taking place in chloroplasts. This includes nitrogen and sulphur assimilation, nucleotide – the building blocks of DNA – and hormone production, as well as the fundamentals of photosynthesis.
This discovery also provides an important new player that could allow engineering of these processes for more productive, sustainable and efficient crops of the future.
Background to the research
The link between photosynthesis and GLK transcription factors was first identified in maize from a forward genetic screen that searched for genetic mutations in plants with low chlorophyll. This led to research showing that GLK controlled chloroplast development in all land plants.
The Cambridge team observed, however, that plants with multiple genetic mutations that had lost the function of GLK are pale but not completely albino, which indicates they still contain some chlorophyll and chloroplasts. This led to the hypothesis that an as yet unknown family of transcription factors operates in parallel with GLK to activate chloroplast development and photosynthesis.
About the research
Since forward genetics had failed to identify components in this alternative pathway, the team concluded that remnant chloroplast development must be controlled by transcription factors encoded by a multi-gene family.
They used the liverwort Marchantia polymorpha to search for new regulators of photosynthesis because of its highly streamlined genome and few multigene families. This work, confirmed by testing in the model plant Arabidopsis thaliana, showed MYB-related transcription factors as controlling chloroplast development and photosynthesis.
Detailed testing included analysis of chlorophyll content and photosynthetic capacity, confocal scanning laser microscopy, electron microscopy, as well as global analysis of gene expression. This confirmed these MYB-related transcription factors as a new class of transcription factor for the control of chloroplast development and photosynthesis.
Next steps
Photosynthesis and chloroplasts respond to the external environment (light) and the cell (hormones). We do not know yet how the MYB-related genes respond to these cues, nor do we know how they interact with all other components helping to induce photosynthesis and build chloroplasts. This is an important area to study in the future.
Reference: Eftychios Frangedakis, Nataliya E. Yelina, Kumari Billakurthi, Lei Hua, Tina Schreier, Patrick J. Dickinson, Marta Tomaselli, Jim Haseloff, Julian M. Hibberd, MYB-related transcription factors control chloroplast biogenesis, Cell, 2024, ISSN 0092-8674, https://doi.org/10.1016/j.cell.2024.06.039.
Image: Left: Marchantia control and RR-MYB double mutant plants. Right: Arabidopsis wild type and RR-MYB double mutant plants, Bottom: confocal microscopy images showing the reduced chloroplast size in the mutants. Images taken from the 'MYB-related transcription factors control chloroplast biogenesis' paper, Cell, 2024.