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It has long been assumed that light activates chloroplastic gene expression via so-called thiol-mediated redox regulation. However, the mechanism giving rise to this regulation has remained elusive until now. Åsa Strand and her group at the Umeå Plant Science Centre have now identified the components involved in this redox regulatory mechanism. Their results are published in the journal Nature Communications.
The chloroplast is the place in the cell where photosynthesis occurs. When a seedling comes out of the soil, it gradually turns green, and during this greening process the photosynthetic machinery in the chloroplasts develops and becomes fully functional. The establishment of photosynthesis is a complicated process that involves the activation of gene expression in the chloroplast in response to light. Åsa Strand and her group identified a component that connects the light signal to the activation of gene expression in the chloroplast.
Proteins - Thioredoxins - Transfer - Electrons - Light
It was demonstrated that certain proteins, called thioredoxins, transfer electrons, primarily derived from light, to the protein PRIN2 (PLASTID REDOX INSENSITIVE2). PRIN2 becomes reduced and changes its structure from a dimer (i.e. two PRIN2 proteins are bound together) to a monomer (single proteins). The PRIN2 monomers then activate photosynthetic gene expression in the chloroplast. This type of regulation is called thiol-mediated redox-regulation because the functional chemical group mediating the transfer of electrons is the sulphur containing thiol group.
"We identified PRIN2 several years ago. We knew that it was sensitive to redox changes and...
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