For almost 30 years, researchers have sought to identify a particular enzyme that is involved in regulating electron transport during photosynthesis. Plants have two photosystems, PSI and PSII that aid in photosynthesis
Linear electron transport requires the participation of both PSI and PSII. Electrons that follow the major route are passed via an acceptor called plastoquinone to the cytochrome b6f complex and from there back to PSI. The identity of the carrier that donates electrons to plastoquinone, and thus makes the process of cyclic electron flow possible, has long been a subject of controversy ,they has now succeeded in identifying the crucial missing link in the process.
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Bioinformatics Centre (DIC)
Photosynthesis: The Last Link in the Chain
Plants can switch between linear and cyclic modes of electron transport in order to maintain the appropriate balance between ATP and NADPH. An electron transporter called ferredoxin, which receives electrons directly from PSI, acts as the junction that connects the two. It was therefore proposed that a so-called ferredoxin-plastoquinone reductase (FQR) must exist, which ensures that electrons can be re-injected into the electron transport chain, and thus allows for cyclic electron transport, but despite intensive searches, no such enzyme had been found.
In 2008, a protein called PGRL1 was identified and it was able to interact with PSI and with other factors known to participate in cyclic electron transport. It turns out that the protein is the long-sought FQR that plays a central role in the regulation of cyclic electron flow. Pivotal regulators such as PGRL1 could be used to enhance the efficiency of photosynthesis and thus increase yields in crop plants grown under controlled conditions.
Courtesy: Bioinformatics Centre, KAU
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