The role of BST4 in the pyrenoid of Chlamydomonas reinhardtii.

TY - UNPB

T1 - The role of BST4 in the pyrenoid of Chlamydomonas reinhardtii.

AU - Adler, Liat

AU - Lau, Chun Sing

AU - Shaikh, Kashif M

AU - van Maldegem, Kim A

AU - Payne-Dwyer, Alex L

AU - Lefoulon, Cecile

AU - Girr, Philipp

AU - Atkinson, Nicky

AU - Barrett, James

AU - Emrich-Mills, Tom Z

AU - Dukic, Emilija

AU - Blatt, Michael R

AU - Leake, Mark C

AU - Peltier, Gilles

AU - Spetea, Cornelia

AU - Burlacot, Adrien

AU - McCormick, Alistair J

AU - Mackinder, Luke C M

AU - Walker, Charlotte E

PY - 2023/11/17

Y1 - 2023/11/17

N2 - In many eukaryotic algae, CO 2 fixation by Rubisco is enhanced by a CO 2-concentrating mechanism, which utilizes a Rubisco-rich organelle called the pyrenoid. The pyrenoid is traversed by a network of thylakoid-membranes called pyrenoid tubules, proposed to deliver CO 2. In the model alga Chlamydomonas reinhardtii ( Chlamydomonas), the pyrenoid tubules have been proposed to be tethered to the Rubisco matrix by a bestrophin-like transmembrane protein, BST4. Here, we show that BST4 forms a complex that localizes to the pyrenoid tubules. A Chlamydomonas mutant impaired in the accumulation of BST4 ( bst4 ) formed normal pyrenoid tubules and heterologous expression of BST4 in Arabidopsis thaliana did not lead to the incorporation of thylakoids into a reconstituted Rubisco condensate. Chlamydomonas bst4 mutant did not show impaired growth at air level CO 2. By quantifying the non-photochemical quenching ( NPQ) of chlorophyll fluorescence, we show that bst4 displays a transiently lower thylakoid lumenal pH during dark to light transition compared to control strains. When acclimated to high light, bst4 had sustained higher NPQ and elevated levels of light-induced H 2O 2 production. We conclude that BST4 is not a tethering protein, but rather is an ion channel involved in lumenal pH regulation possibly by mediating bicarbonate transport across the pyrenoid tubules.

AB - In many eukaryotic algae, CO 2 fixation by Rubisco is enhanced by a CO 2-concentrating mechanism, which utilizes a Rubisco-rich organelle called the pyrenoid. The pyrenoid is traversed by a network of thylakoid-membranes called pyrenoid tubules, proposed to deliver CO 2. In the model alga Chlamydomonas reinhardtii ( Chlamydomonas), the pyrenoid tubules have been proposed to be tethered to the Rubisco matrix by a bestrophin-like transmembrane protein, BST4. Here, we show that BST4 forms a complex that localizes to the pyrenoid tubules. A Chlamydomonas mutant impaired in the accumulation of BST4 ( bst4 ) formed normal pyrenoid tubules and heterologous expression of BST4 in Arabidopsis thaliana did not lead to the incorporation of thylakoids into a reconstituted Rubisco condensate. Chlamydomonas bst4 mutant did not show impaired growth at air level CO 2. By quantifying the non-photochemical quenching ( NPQ) of chlorophyll fluorescence, we show that bst4 displays a transiently lower thylakoid lumenal pH during dark to light transition compared to control strains. When acclimated to high light, bst4 had sustained higher NPQ and elevated levels of light-induced H 2O 2 production. We conclude that BST4 is not a tethering protein, but rather is an ion channel involved in lumenal pH regulation possibly by mediating bicarbonate transport across the pyrenoid tubules.

U2 - 10.1101/2023.06.15.545204

DO - 10.1101/2023.06.15.545204

M3 - Preprint

C2 - 38014171

T3 - bioRxiv : the preprint server for biology

BT - The role of BST4 in the pyrenoid of Chlamydomonas reinhardtii.

PB - bioRxiv, at Cold Spring Harbor Laboratory

ER -