Evolution of light-harvesting complex proteins from Chl c-containing algae

<p>Abstract</p> <p>Background</p> <p>Light harvesting complex (LHC) proteins function in photosynthesis by binding chlorophyll (Chl) and carotenoid molecules that absorb light and transfer the energy to the reaction center Chl of the photosystem. Most research has focused on LHCs of plants and chlorophytes that bind Chl <it>a </it>and <it>b </it>and extensive work on these proteins has uncovered a diversity of biochemical functions, expression patterns and amino acid sequences. We focus here on a less-studied family of LHCs that typically bind Chl <it>a </it>and <it>c</it>, and that are widely distributed in Chl <it>c</it>-containing and other algae. Previous phylogenetic analyses of these proteins suggested that individual algal lineages possess proteins from one or two subfamilies, and that most subfamilies are characteristic of a particular algal lineage, but genome-scale datasets had revealed that some species have multiple different forms of the gene. Such observations also suggested that there might have been an important influence of endosymbiosis in the evolution of LHCs.</p> <p>Results</p> <p>We reconstruct a phylogeny of LHCs from Chl <it>c</it>-containing algae and related lineages using data from recent sequencing projects to give ~10-fold larger taxon sampling than previous studies. The phylogeny indicates that individual taxa possess proteins from multiple LHC subfamilies and that several LHC subfamilies are found in distantly related algal lineages. This phylogenetic pattern implies functional differentiation of the gene families, a hypothesis that is consistent with data on gene expression, carotenoid binding and physical associations with other LHCs. In all probability LHCs have undergone a complex history of evolution of function, gene transfer, and lineage-specific diversification.</p> <p>Conclusion</p> <p>The analysis provides a strikingly different picture of LHC diversity than previous analyses of LHC evolution. Individual algal lineages possess proteins from multiple LHC subfamilies. Evolutionary relationships showed support for the hypothesized origin of Chl <it>c </it>plastids. This work also allows recent experimental findings about molecular function to be understood in a broader phylogenetic context.</p

Mollistephaninae and Frebolditinae, new subfamilies of Middle Jurassic stephanoceratid Ammonoidea

Two new Bajocian stephanoceratid subfamilies are distinguished based on morpho-structural criteria and phyletic patterns. At the Aalenian/Bajocian transition, Stephanoceratinae of the genus Albarracinites are the source of the earliest species of Mollistephanus and of the new Mollistephaninae lineage that includes three successive genera: Mollistephanus, Paramollistephanus gen. nov. and Phaulostephanus. The Mollistephaninae span across the Mediterranean-Caucasian Subrealm during the lower Bajocian, but Paramollistephanus is pandemic to both the Mediterranean-Caucasian and East Pacific subrealms during the Propinquans Zone. The Frebolditinae evolved from Paramollistephanus in the lower Bajocian, beginning with Freboldites and giving rise to diverse genera such as Parabigotites, Patrulia, Bajocia, Subcollina and Parastrenoceras that occur into the upper Bajocian of both the East Pacific and Mediterranean-Caucasian subrealms. Palaeobiogeographical and phylogenetic data of these two subfamilies support an active Bajocian Central-Atlantic Seaway, the so-called Hispanic Corridor, as a bidirectional, biodispersal route driven by changes of the relative sea level. Several bioevents of appearance, immigration and dispersal, associated with the range expansion of ammonoid taxa, were effective (Paramollistephanus in the latest Laeviuscula Zone, Subcollina in the latest Humphriesianum Zone, and Parastrenoceras in the earliest Niortense Zone). Based on life-history strategy, morpho-structural and functional criteria, the dimorphic Caumontisphinctes- Infraparkinsonia pair seems to be the origin of the Parkinsoniidae. The Mollistephaninae and Frebolditinae show small adult size, scarcity of fossils, and low stratigraphic persistence and constancy; however, they present some pandemic genera of the Tethys-Panthalassa Realm and display high resolution for time correlation between the western Tethyan and eastern Pacific marine basins of separate bioprovinces