Fig. 3.

saga1 mutant cells have multiple pyrenoids and often lack thylakoid tubules. (A) Representative TEMs of wild-type, saga1, and saga1;SAGA1-Venus cells grown at low CO₂, illustrating the frequent observation of multiple pyrenoids in saga1. (Scale bar, 500 nm.) (B) Representative immunogold staining images of wild type and saga1 pyrenoids using an anti-Rubisco antibody. (Scale bar, 500 nm.) (C) The fraction of cells containing visible pyrenoids in wild-type, saga1, and saga1;SAGA1-Venus cells grown at low CO₂ (n = 30 fields of view; Mann–Whitney U test). (D) The fraction of pyrenoid-containing cells that contain more than 1 pyrenoid in wild-type, saga1, and saga1;SAGA1-Venus cells grown at low CO₂ (n = 30 fields of view; Mann–Whitney U test). (E) Pyrenoid matrix cross-sectional area in wild-type, saga1, and saga1;SAGA1-Venus cells grown at low CO₂ (n = 20 pyrenoids). (F) Representative summed z-stacks of wild-type and saga1 cells constitutively expressing RBCS1-mCherry (green) grown in low CO₂. Magenta is chlorophyll autofluorescence. (Scale bar, 1 μm.) (G) Quantification of the number of RBCS1-mCherry puncta per cell (wild type: 1.2 ± 0.7 puncta per cell; saga1: 9.6 ± 4.1; n = 35 cells, Mann–Whitney U test). (H) Quantification of the fraction of pyrenoids with visible thylakoid tubules (n = 30 fields of view; Mann–Whitney U test). (I) The number of thylakoid tubules per pyrenoid in wild-type, saga1, and saga1;SAGA1-Venus cells grown at low CO₂ (n = 20 pyrenoids, Mann–Whitney U test). Error bars: SEM; n.s., not significant; P ≥ 0.05; *P < 0.05; **P < 0.001.