Dark deactivation of chloroplast enzymes finally comes to light

Abstract

From the pioneering work that the Buchanan group started in the late 1960s, we know that the division of photosynthesis into light and dark reactions is inadequate because the activity of a number of chloroplast enzymes, many involved in the Calvin–Benson cycle, is strictly controlled by light; that is, they are activated in the light and deactivated in the dark. An exception is glucose-6-phosphate dehydrogenase, which is regulated in an opposite manner; that is, activation in the dark and deactivation in the light. It took a decade to biochemically dissect the newly identifed redox regulatory pathway responsible for this regulation. Known as the ferredoxin-thioredoxin system, the pathway is composed of three components: ferredoxin, ferredoxin-thioredoxin reductase (FTR), and thioredoxin (Trx) that relay the reducing power generated at photosystem 1 (PSI) to target regulatory enzymes (1, 2). Over the last four decades there have been a number of milestones in the field of redox regulation in plants. The first step was to identify ferredoxin, FTR, and Trx as key components of the regulatory system. We then observed that there were multiple Trxs with differential selectivities in plant eukaryotic cells, and although this seems of little significance now, in the genomic era it was the subject of intense debate at the time. A very important contribution was the elucidation of the 3D structures and catalytic mechanisms of FTRs and Trxs. A lot of effort has also been … [↵][1]1Email: j2p{at}univ-lorraine.fr. [1]: #xref-corresp-1-1