In the unicellular red alga Rhodella violacea iron deficiency induces an accumulation of uncoupled LHC.

Iron plays a key role in the synthesis and functioning of the photosynthetic apparatus. Conditions of partial iron deficiency that lead to a relatively stable phenotype were established and the effects of starvation studied in the unicellular red alga, Rhodella violacea. Synthesis of the photosynthetic pigments were found to decrease, with phycobiliproteins being affected to a lesser extent than chlorophyll a. Biophysical, biochemical and immunological approaches were used to show that the PSI content is highly diminished and the PSII/PSI stoichiometry increased by a factor of 5 compared to standard conditions. Meanwhile light-harvesting complex (LHC) was still assembled in the thylakoid membranes at unchanged levels. The use of translation inhibitors for either nuclear- or plastid-encoded polypeptides revealed that uncoupled LHC may be responsible for the high wavelength-fluorescence contribution observed around 700-710 nm. There is no evidence for the synthesis of new chlorophyll-protein complexes.