The first photopigment that existed on Earth

A recent study, based on advanced computational modeling, has explored how it could be the first solar radiation-capturing pigment, simpler than those currently in existence, and which would be the common ancestor of the current photopigments involved in photosynthesis.

The research has been led by the Center for Astrobiology (CAB), dependent on the Higher Council for Scientific Research (CSIC) and the National Institute for Aerospace Technology (INTA), all these institutions in Spain.

Delving into the evolutionary retrospective of this type of compound, the authors of the study have reached the conclusion that the first photopigments of which there is evidence are too complex and evolved and that on the primitive Earth there must have been a “zero” photopigment, at that they have baptized as Phot0, prior to these and of which there has been no fossil record.

Its synthesis had to take place in hostile conditions with volcanic activity, high temperatures and the presence of zinc, a heavy metal that acted as a catalyst. The interaction of water vapor with volcanic contents on the early Earth would have allowed the formation of this common primitive pigment.

As stated by Felipe Gómez, CAB researcher and head of the group that has carried out this work, “From the scientific community it has been assumed that photosynthesis appeared on the primitive Earth shortly after the origin of life. Now, knowing that this photopigment could appear in an environment like the one we describe in this study, we wonder if the emergence of photosynthesis could be coeval with the very origin of life”. Thus, the question of whether the origin of life could have been photosynthetic could be amenable to further study.

The study has been a cover article in the academic journal PCCP, where it has been published. Here we see the image of said cover, which illustrates what was investigated in the study and the findings that have been made. (Image: PCCP)

Photosynthesis is a fundamental chemical process for the existence of life as we know it, since it transforms inorganic matter into organic matter using sunlight. Until now, it was thought that the complex biomolecules that allowed photosynthesis to take place on the early Earth were synthesized through complex and evolved metabolic pathways.

In the words of Juan García de la Concepción, CAB researcher and co-author of this study, “Our work casts doubt on this hypothesis and proposes a simpler process of geochemical origin, which links to the possibility that photosynthesis may occur in the hostile environments of certain exoplanets.

To dispel this doubt, the team has analyzed stellar radiation data on rocky exoplanets similar to Earth, finding that the Phot0 hypothesis fits with the typical geochemical conditions of these environments.

The theoretical results obtained by the team show that geochemical conditions may exist that allow the abiotic formation (that is, that does not imply the presence of life) of a primordial pigment that could become sufficiently abundant in the early stages of rocky exoplanets. livable.

Therefore, instead of biochemical transformations occurring on a very young planet, the pigment would appear before life thanks to purely chemical pathways, and perhaps suppose a first step for the very origin of life. (Source: CAB / CSIC / INTA)