The light-harvesting proteins (LHC) in plastids of different lineages including algae and land plants represent a superfamily of chlorophyll-binding proteins that seem to be phylogenetically related although some of the LHC proteins bind different carotenoids. LHCs can be divided into chlorophyll a/b-binding proteins found in green algae, euglenoids and higher plants and into chlorophyll a/c-binding proteins of various algal taxa. LHC-proteins from diatoms are named fucoxanthin-chlorophyll-a,c-binding-proteins (FCP). In contrast to chlorophyll-a/b-binding proteins there is no information so far about the way FCPs integrate into thylakoid membranes. The diatom FCP-preproteins have a bipartite presequence which is necessary to enable transport into the four-membrane bound diatom plastids, but similar to chlorophyll-a/b-binding proteins there is apparently no presequence present for targeting to the thylakoid membrane. By establishing an in vitro import assay for diatom thylakoids we demonstrated that thylakoid integration of diatom FCP depends on the presence of stromal factors and GTP. This indicates that a pathway involving signal recognition particles (SRP) is involved in membrane integration just as shown for LHCs in higher plants. We also demonstrate integration of diatom FCP into thylakoids of higher plants and vice versa SRP-dependent targeting of LHCs from pea and Arabidopsis into diatom thylakoids. The similar SRP-dependent modes of thylakoid integration of land plant LHCs and FCPs support recent analyses indicating a common origin of chlorophyll a/b- and a/c-binding proteins.