Time-resolved comparative molecular evolution of oxygenic photosynthesis

“…2B and Fig. 3) as we have detailed in previous discussions (Cardona 2019, Oliver et al 2021, but see also (Gisriel et al 2021).…”

“…In other words, it must antedate the diversification events leading to the phylum-specific reaction centre proteins. Because the relationship between type I and II reaction centres is unambiguous, it can be concluded unequivocally that the evolutionary events leading to type I and II occurred, at the very least, near the root of the tree of life of Bacteria, but likely before that when other relationships are taken into consideration, as described next, but see also Oliver et al (2021). The large amount of sequence change (i.e.…”

“…The evidence can be seen in gene trees, which tend to match the species tree, as well as in synteny, and in supporting evidence such as GC% (Table S9). Different genes were suggested to have entered the cluster at different times, with the earliest being the chl f synthase 39,55 . In contrast, PSI genes were suggested to have emerged later, thereby requiring HGT to explain gene presence in early lineages 38 .…”

“…This, together with long and short motifs resulting from duplications, has been maintained across evolutionary time, some perhaps since the MRCA (2.2 -2.5 billion years ago) 5,6 . The high conservation within the chlF motifs, combined with the high level of expression of the gene within the cluster [48][49][50] , and with the fact that this is the oldest FaRLiP gene 39,55 , underscores the vital role of the chlf synthase in FaRLiP. However, the co-transcription of chlF and psa genes in early lineages (V, VI) also suggests that PSI genes may have played an important role in early FaRLiP evolution.…”

“…More speculatively, these results may also help answer the question posed as to why plants use chlorophyll with a peak absorbance in the red (680 nm), rather than just at other more energetic wavelengths (Kiang et al., 2007). The earliest photosynthetic organisms appear to have developed some 3.5 billion or more years ago (Oliver et al., 2021) under an anaerobic atmosphere containing organic hazes which absorbed strongly in the blue and ultraviolet end of the spectrum (Sagan & Chyba, 1997; Wolf & Toon, 2010). The origin of oxygenic photosynthesis utilising red light, in what therefore must have been a shallow sea, makes sense as these were the only range of wavelengths available.…”