Fig. 1

Characterization of pale-green-14 (PG-14) mutant of Chlorella vulgaris. a PSII functional antenna size. Variable Chl fluorescence was induced with a green light (15 μmol photons m⁻² s⁻¹), on dark-adapted cells of WT and PG-14, in BG-11 medium supplemented with 50 μM DCMU. Data are expressed as mean ± SD, n = 10. The reciprocal of time corresponding to two-thirds of the fluorescence rise (T_2/3) was taken as a measure of the PSII functional antenna size (see Table 1). b Immunoblotting used for the quantification of photosynthetic subunits. Immunotitration was performed with antibodies directed against individual gene products: LHCII, the major light harvesting complex of PSII; the PSII core subunit PsbC (CP43); the PSI core subunit (PsaA). The amount of Chls loaded for each lane is shown. Values significantly different (Student’s t test, p < 0.05) with respect to the WT are marked with asterisks. c Light-saturation curves of photosynthesis. Measured cultures (panels a–c) were grown in minimal BG-11 medium at 100 μmol photons m⁻² s⁻¹, in shaken flasks (120 rpm) illuminated from the top, photoperiod of 16/8 h light/dark, 25 °C. d Growth curves of wild type and PG-14 mutant under autotrophic conditions. All experiments were performed in 1-L cylinders, illuminated with 1400 μmol photons m⁻² s⁻¹, 25 °C. Growths were performed in a semi-batch system fed with air/CO₂ mix; the CO₂ supply was modulated to keep the pH of the medium always below 7.1. Data are expressed as mean ± SD, n = 4