Title: Properties of cyanobacterial UV-absorbing pigments suggest their evolution was driven by optimizing photon dissipation rather than photoprotection,
Abstract: An ancient repertoire of UV absorbing pigments which survive today in the
phylogenetically oldest extant photosynthetic organisms the cyanobacteria point
to a direction in evolutionary adaptation of the pigments and their associated
biota from largely UVC absorbing pigments in the Archean to pigments covering
ever more of the longer wavelength UV and visible in the Phanerozoic.Such a
scenario implies selection of photon dissipation rather than photoprotection
over the evolutionary history of life.This is consistent with the thermodynamic
dissipation theory of the origin and evolution of life which suggests that the
most important hallmark of biological evolution has been the covering of Earths
surface with organic pigment molecules and water to absorb and dissipate ever
more completely the prevailing surface solar spectrum.In this article we
compare a set of photophysical photochemical biosynthetic and other germane
properties of the two dominant classes of cyanobacterial UV absorbing pigments
the mycosporine like amino acids MAAs and scytonemins.Pigment wavelengths of
maximum absorption correspond with the time dependence of the prevailing Earth
surface solar spectrum and we proffer this as evidence for the selection of
photon dissipation rather than photoprotection over the history of life on
Earth.