Photosynthetic “missing link” to malaria pathogen found
I recently wrote about how the endosymbiotically-derived apicoplast in P. falciparum fits very well with evolution, and is nonsensical as “design”. What I did not realize when I was writing that post, even though I had read the News and Views version in Nature when the research results were published (it was not very important to me at the time), was that a related organism has recently been found which still uses for photosynthesis a chloroplast which descended from the ancestral chloroplast from which P. falciparum’s apicoplast had also been derived. This is even further evidence which is explained by, and predicted in aspects via, evolution–and never once has such an intricate and step-wise production of a nested hierarchy of “machines” been seen as a design strategy in actions effected by any observable designer.
One of the predictions of evolution is that in nearly all adaptive radiations there will be a variety of adaptations of an organ, organelle, or system which is undergoing selective pressure. Of course there is no guarantee that any of the variations will survive or fossilize, nor that if one variant survives or fossilizes, another variant will. However, not infrequently are variations of a particular evolving system or entity found, thereby confirming the pattern expected of non-teleological evolution. The discovery of the the photosynthetic Chromera velia apparently is one such find which is so closely related to the apicomplexans (and shares a red-alga-derived photosynthetic plastid with some of the more distantly related Dinoflagellates), such as P. falciparum, that it seems unlikely that their respective plastids would not have a common origin.
Indeed, how would anyone even think through the shared plastid features of C. velia and P. falciparum except via evolutionary theory? Why would P. falciparum even have a plastid derived from a cyanobacterium, when the two only share a relatively few pathways at present? Would not a real designer just transfer the design of the pathways (or come up with a new pathway expressly designed for P. falciparum, if the designer is God), either with or without a single or double membrane (it appears P. falciparum has three membranes in its plastid, apparently down from four after its secondary symbiotic origin (double membrane from the cyanobacterium plus a double membrane from the red alga))?
Anyway, those are issues to think about when reading the following excerpts of the article:
[Abstract] Many parasitic Apicomplexa, such as Plasmodium falciparum, contain an unpigmented chloroplast remnant termed the apicoplast, which is a target for malaria treatment. However, no close relative of apicomplexans with with a functional photosynthetic plastid has yet been described. Here we describe a newly cultured organism that has ultrastructural features typical for alveolates, is phylogenetically related to apicomplexans, and contains a photosynthetic plastid. The plastid is surrounded by four membranes, is pigmented by chlorophyll α, and uses the codon UGA to encode tryptophan in the psbA gene. this genetic feature has been found only in coccidian apicoplasts and various mitochondria. The UGA-Trp codon and phylogenies of plastid and nuclear RNA genes indicate that the organism is the closest known photosynthetic relative to apicomplexan parasites and that its plastid shares an origins with the apicoplasts. The discovery of this organism provides a powerful model with which to study the evolution of parasitism in Apicomplexa. p. 959 Moore, et al. “A photosynthetic alveolate closely related to apicomplexan parasites” Nature 21 Feb. 2008 451:959-963
And here is the concluding paragraph:
Phylogenetic analyses support the description of Chromera velia as an alveolate, possessing a photosynthetic plastid that lies in the same secondary endosymbiotic lineage as apicoplasts. The ultrastructure and photosynthetic pigment profile of C. velia are consistent with a chromalveolate-affiliated ancestry. Figure 3 presents a model of the evolutionary history of C. velia, apicomplexans and dinoflagellates based on the phylogeny of the nuclear and plastid lineages and the retention or loss of plastid characteristics. Chromera velia represents the closest known photosynthetic relative of apicomplexan parasites. Ibid. p. 962
Well, there it is, more evidence that a series of historical accidents lie behind the “irreducibly complex” phenomena of malaria pathogens, along with adaptation of these hereditary and event-produced accidents. Perhaps Behe would be a whole lot more convincing with respect to his design claims if he could elucidate some features of any organism which differed substantially from accident and adaptation, rather than trying to claim, based on nothing but ignorance, that what appears to be the result of accident plus selection must be ruled by some super-intelligent being, but without rationally intelligent responses to needs ever having been made.
This is part of a series of posts that I am combining into one long post, which may be found at The Edge of Evolution