Fig. 5. Subcellular localization of FcR1 and phytoplankton phenotyping assays.

a,b, Localization of FcR1::eGFP fusion protein after expression in the pennate diatom P. tricornutum (a) and in the centric diatom T. pseudonana (b), including untransformed wild-type control strains (PtWT and TpWT, respectively). Shown are Normarski DIC, green fluorescence protein (GFP) and red chlorophyll autofluorescence (Alexa568). Representative micrographs of five independent experiments are shown. Scale bars, 5 µm. c, Growth of iron-limited F. cylindrus under green and red LEDs (n = 3). d, Growth of nutrient-replete F. cylindrus under green and red LEDs (n = 3). e, Spectral wavelength of green and red LEDs (n = 1). f, Growth of T. pseudonana rhodopsin knock-in gain-of-function (KI) mutant (TpFcR1, sky blue) and wild-type (TpWT, reddish purple) under iron limitation (150 nM) and constant white light (38 µmol photons m⁻² s⁻¹). Exponential growth phase to determine growth rates is highlighted as a grey-shaded box. g, Growth of T. pseudonana rhodopsin knock-in gain-of-function (KI) mutant (TpFcR1, sky blue) and wild type (TpWT, reddish purple) in nutrient-replete medium and constant white light (38 µmol photons m⁻² s⁻¹). Exponential growth phase to determine growth rates is highlighted as a grey-shaded box. h, Growth rates of T. pseudonana rhodopsin knock-in mutant (TpFcR1, sky blue) and T. pseudonana wild type (TpWT, reddish purple) under constant white light (38 µmol photons m⁻² s⁻¹) during iron-limited and nutrient-replete growth. i, Maximum cell abundance of T. pseudonana rhodopsin knock-in mutant (TpFcR1, sky blue) and T. pseudonana wild type (TpWT, reddish purple) under constant white light (38 µmol photons m⁻² s⁻¹) during nutrient-replete and iron-limited growth. Statistics are displayed as mean ± s.d. (n = 5) and the P values displayed were determined using two-sided Wilcoxon rank-sum test (h,i). (Credit for diatom illustrations of F. cylindrus (c,d) and T. pseudonana (f,g) to Charlotte Eckmann).

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