RESUMEN
Glaucophytes are the least studied of the three major Archaeplastida (Plantae sensu lato) lineages. It has been largely recognized that comprehensive investigations of glaucophyte genetic and species diversity will shed light on the early evolution of photosynthetic eukaryotes. Here we used molecular phylogenetics and genetic distance estimations of diverse molecular markers to explore strain and species diversity within the glaucophyte genera Cyanophora and Glaucocystis. Single gene and concatenated maximum likelihood analyses of markers from three different genetic compartments consistently recovered similar intrageneric genetic groups. Distance analyses of plastid (psbA and rbcL) and mitochondrial (cob and cox1) genes, and the nuclear internal transcribed spacer (ITS) region, revealed substantial genetic divergence between some Cyanophora paradoxa and Glaucocystis nostochinearum strains. The genetic distances estimated between some glaucophyte strains currently considered the same species are similar or greater than divergence values calculated between different species in other unicellular algae, such as certain green algae and diatoms. The analyzed molecular markers are prospective candidates for future studies of species diversity in glaucophytes. Overall, our results unveil previously unrecognized cryptic diversity within Cyanophora and Glaucocystis species.
Asunto(s)
Cyanophora/genética , Variación Genética/genética , Genoma/genética , Glaucophyta/genética , Filogenia , Núcleo Celular/genética , Chlorophyta/genética , Cyanophora/citología , Código de Barras del ADN Taxonómico , Diatomeas/genética , Marcadores Genéticos/genética , Genómica , Glaucophyta/citología , Corea (Geográfico) , Mitocondrias/genética , América del Norte , Plastidios/genética , Análisis de Secuencia de ADNRESUMEN
Chloroplasts have evolved from a cyanobacterial endosymbiont and their continuity has been maintained by chloroplast division, which is performed by the constriction of a ring-like division complex at the division site. It is believed that the synchronization of the endosymbiotic and host cell division events was a critical step in establishing a permanent endosymbiotic relationship, such as is commonly seen in existing algae. In the majority of algal species, chloroplasts divide once per specific period of the host cell division cycle. In order to understand both the regulation of the timing of chloroplast division in algal cells and how the system evolved, we examined the expression of chloroplast division genes and proteins in the cell cycle of algae containing chloroplasts of cyanobacterial primary endosymbiotic origin (glaucophyte, red, green, and streptophyte algae). The results show that the nucleus-encoded chloroplast division genes and proteins of both cyanobacterial and eukaryotic host origin are expressed specifically during the S phase, except for FtsZ in one graucophyte alga. In this glaucophyte alga, FtsZ is persistently expressed throughout the cell cycle, whereas the expression of the nucleus-encoded MinD and MinE as well as FtsZ ring formation are regulated by the phases of the cell cycle. In contrast to the nucleus-encoded division genes, it has been shown that the expression of chloroplast-encoded division genes is not regulated by the host cell cycle. The endosymbiotic gene transfer of minE and minD from the chloroplast to the nuclear genome occurred independently on multiple occasions in distinct lineages, whereas the expression of nucleus-encoded MIND and MINE is regulated by the cell cycle in all lineages examined in this study. These results suggest that the timing of chloroplast division in algal cell cycle is restricted by the cell cycle-regulated expression of some but not all of the chloroplast division genes. In addition, it is suggested that the regulation of each division-related gene was established shortly after the endosymbiotic gene transfer, and this event occurred multiple times independently in distinct genes and in distinct lineages.