It was a zoological sensation when a living specimen of the coelacanth was first discovered in 1938, as this lineage of lobe-finned fish was thought to have gone extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features . Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain, and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues demonstrate the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution.

SARS-CoV-2, EBOV and emerging RNA viruses are amongst the most important global health threats; yet clinically approved antiviral drugs are available for only 10 of the more than 220 viruses known to infect humans.

Following the first description of living marine stromatolites along the South African east coast, new investigations along the south coast have revealed the occurrence of extensive fields of actively calcifying stromatolites. These stromatolites have been recorded at regular distances along a 200-km stretch of coastline, from Cape Recife in the east to the Storms River mouth in the west, with the highest density found between Schoenmakerskop and the Maitland River mouth. All active stromatolites are associated with freshwater seepage streams flowing from the dune cordon, which form rimstone dams and other accretions capable of retaining water in the supratidal platform. Resulting pools can reach a maximum depth of about 1 m and constitute a unique ecosystem in which freshwater and marine organisms alternate their dominance in response to vertical mixing and the balance between freshwater versus marine inflow. Although the factors controlling stromatolite growth are yet to be determined, nitrogen appears to be supplied mainly via the dune seeps. The epibenthic algal community within stromatolite pools is generally co-dominated by cyanobacteria and chlorophytes, with minimal diatom contribution.

Expression of the nitrogen catabolic genes in Saccharomyces cerevisiae, including those of the -y-aminobutyric acid (UGA) and allantoin (DAL) pathways, is regulated positively by the GLN3 protein and negatively by the DAL80 protein. The deduced sequences of the DALSO and GLN3 proteins contain a zinc finger motif homologous to those shown to bind GATA sequences. In addition, DAL80 protein has been directly shown to bind to a pair of GATA-containing sequences (URSGATA) in vitro, and a pair of GATA-containing sequences (UASNTR) is required for GLN3-dependent transcriptional activation in a heterologous expression vector. We demonstrate here that the GATA-containing sites upstream of UGA4 required for optimal GLN3-dependent transcriptional activation also mediate DAL80 protein binding in vitro and DAL80-responsive regulation in vivo.The expression of most genes whose products participate in nitrogen catabolism in Saccharomyces cerevisiae is controlled by two global transcriptional regulators, the GLN3 and DAL80 proteins (14,15). GLN3 is required for transcriptional activation mediated by UASNTR, the upstream activation sequence responsible for nitrogen catabolite repression (NCR)-sensitive transcription (14). Detailed genetic analysis has demonstrated that UASNTR consists of two dodecanucleotide elements with the sequence GATAA at their cores (3,19). There is also tentative evidence that GLN3 protein binds to UASNTR; i.e., antibody against GLN3 protein has been reported to coimmunoprecipitate a synthetic DNA fragment containing seven UASNTR-homologous sequences (14). The finding that deletion of DAL80 results in overexpression of most NCR-sensitive genes has led to the conclusion that DAL80 protein globally participates in transcriptional repression (4)(5)(6)8). Consistent with this role, DAL80 has been shown to be a DNA-binding protein that binds to the cis-acting element URSGATA in vitro (7). Optimally, URSGATA consists of a pair of elements, each containing a GATAA sequence at its core, separated by 15 or more nucleotides and oriented tail-to-tail or head-to-tail (7). The deduced amino acid sequences of the DAL80 and GLN3 proteins are also consistent with the suggestion that both proteins function through cis-acting sites which contain the sequence GATA at their cores, i.e., UASNTR-and URSGATAhomologous sequences (5,6,14). In particular, both proteins contain a zinc finger motif that is homologous to those contained in the metazoan GATA family of DNA-binding proteins as well as to the fungal ARE2 and NIT2 proteins (5, 6, 9, 12, 14). The three-dimensional structure of one such zinc finger-DNA complex has recently been determined by nuclear magnetic resonance spectral analysis (16).The above-described observations suggest that UASNTR and URSGATA sites upstream of NCR-sensitive, DAL80-regulated genes might overlap. If experimentally substantiated, this * Corresponding author. Phone: (901) 448-8462. suggestion would have significant implications for the types of mechanisms of action proposed for the URSGATA-an...

The Latrunculiidae are a family of cold water sponges known for their production of bioactive pyrroloiminoquinone alkaloids. Previously it was shown that the bacterial community associated with a Tsitsikamma sponge species comprises unusual bacterial taxa and is dominated by a novel Betaproteobacterium. Here, we have characterized the bacterial communities associated with six latrunculid species representing three genera (Tsitsikamma, Cyclacanthia, and Latrunculia) as well as a Mycale species, collected from Algoa Bay on the South African southeast coast. The bacterial communities of all seven sponge species were dominated by a single Betaproteobacterium operational taxonomic unit (OTU 0.03), while a second OTU 0.03 was dominant in the Mycale sp. The Betaproteobacteria OTUs from the different latrunculid sponges are closely related and their phylogenetic relationship follows that of their hosts. We propose that the latrunculid Betaproteobacteria OTUs are members of a specialized group of sponge symbionts that may have coevolved with their hosts. A single dominant Spirochaetae OTU 0.03 was present in the Tsitsikamma and Cyclacanthia sponge species, but absent from the Latrunculia and Mycale sponges. This study sheds new light on the interactions between latrunculid sponges and their bacterial communities and may point to the potential involvement of dominant symbionts in the biosynthesis of the bioactive secondary metabolites.