PT  - JOURNAL ARTICLE
AU  - Zeno Guardini
AU  - Rodrigo L. Gomez
AU  - Roberto Caferri
AU  - Johannes Stuttmann
AU  - Luca Dall’Osto
AU  - Roberto Bassi
TI  - Thylakoid grana stacking revealed by multiplex genome editing of LHCII encoding genes
AID  - 10.1101/2021.12.31.474624
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2021.12.31.474624
4099  - http://biorxiv.org/content/early/2022/01/01/2021.12.31.474624.short
4100  - http://biorxiv.org/content/early/2022/01/01/2021.12.31.474624.full
AB  - Land plant chloroplasts differ from algal ones for their thylakoid membranes being organized in grana: piles of vesicles paired by their stromal surface, forming domains including Photosystem (PS) II and its antenna while excluding PS I and ATPase to stroma membranes, connecting grana stacks. The molecular basis of grana stacking remain unclear. We obtained genotypes lacking the trimeric antenna complex (Lhcb1-2-3), the monomeric Lhcb4-5-6, or both. Full deletion caused loss of grana, while either monomers or trimers support 50% stacking. The expression of Lhcb5 alone restored stacking at 50%, while Lhcb2 alone produced huge grana which broke down upon light exposure. Cyclic electron transport was maintained in the lack of stacking, while excitation energy balance between photosystems and the repair efficiency of damaged Photosystem II were affected. We conclude that grana evolved for need of regulating energy balance between photosystems under terrestrial canopy involving rapid changes in photon spectral distribution.Competing Interest StatementThe authors have declared no competing interest.