Thousands of genes of potential green algal origin have been detected in diatoms, giving rise to the hypothesis that Stramenopiles have undergone a cryptic secondary endosymbiosis with a green alga before acquiring the red algal endosymbiont (Moustafa et al. 2009).
More specifically, cryptophytes have alloxanthin, most heterokonts and haptophytes have fucoxanthin, dinoflagellates with a plastid of red algal origin have peridinin (hereafter "peridinin-containing dinoflagellates"), while dinoflagellates with a plastid of haptophyte origin (hereafter "fucoxanthin-containing dinoflagellates") have a fucoxanthin derivative found in haptophytes [ 17, 25].
Other nuclear-encoded plastid-targeted protein genes, however, are clearly not of green algal origin, but have been derived from a number of different algal groups, including dinoflagellates, streptophytes, heterokonts, and red algae.
The zone of origin had been changed.
Several research groups, including ours, have shown that docosahexaenoic acid (DHA), a lipid of marine algal origin mainly provided by diet, has, experimentally, the ability to increase the efficacy of anti-cancer agents.
The presence of multiple genes of apparent red algal origin in genomes of chromalveolates has been reported (Li et al. 2006).
Chromalveolates were originally defined by their plastid of red algal origin that (when present) is believed to have arisen from a single secondary endosymbiosis [16].
The outermost membrane is connected to the endoplasmic reticulum (ER) in some secondary plastids of red algal origin, and the recent ER-enclosure model has proposed that the outer pair of membranes are derived from the host ER [ 8].
Diatoms and cryptophytes are very distantly related algal groups that share the characteristic of having secondary plastids of red algal origin (Bachvaroff et al. 2005; Burki et al. 2012).
The main novel finding is that postprandial 8-isoprostane F2α production is lower after consumption of a meal enriched with DHA (of algal origin), whereas an FO meal (EPA + DHA) has the opposite effect.
However, this hypothesis has been criticized, and it has been questioned how many genes of green algal origin can actually be detected in diatoms (Burki, Flegontov, et al. 2012; Deschamps and Moreira 2012; Woehle et al. 2011).
