Biology subjects

Martin, W. F.

Publications and source records attributed to Martin, W. F..

3 recordsLinked to original sources

bioRxiv2018

Enlarged and highly repetitive plastome of Lagarostrobos and plastid phylogenomics of Podocarpaceae

Podocarpaceae is the largest family in cupressophytes (conifers II), but their plastid genomes (plastomes) are poorly studied, with plastome data currently existing for only four of the 19 Podocarpaceous genera. In this study, we assembled the plastomes from representatives of eight additional genera, including Afrocarpus, Dacrydium, Lagarostrobos, Lepidothamnus, Microstrobos, Phyllocladus, Prumnopitys, and Saxegothaea. We found that Lagarostrobos, a monotypic genus native to Tasmania, has the largest plastome among any cupressophytes studied to date (151,496 bp). Plastome enlargement in Lagarostrobos coincides with increased intergenic spacers, repeats, and duplicated genes. Among Podocarpaceae, Lagarostrobos has the most rearranged plastome, but its substitution rates are modest. Plastid phylogenomic analyses clarify the positions of previously conflicting Podocarpaceous genera. Tree topologies firmly support the division of Podocarpaceae into two sister clades: (1) the Prumnopityoid clade and (2) the clade containing Podocarpoid, Dacrydioid, Microstrobos, and Saxegothaea. The Phyllocladus is nested within the Podocarpaceae, thus familial status of the monotypic Phyllocladaceae is not supported.

evolutionary biology↗

bioRxiv2018

Lipids are the preferred substrate of the protist Naegleria gruberi, relative of a human brain pathogen

Naegleria gruberi is a free-living non-pathogenic amoeboflagellate and relative of Naegleria fowleri, a deadly pathogen causing primary amoebic meningoencephalitis (PAM). A genomic analysis of N. gruberi exists, but physiological evidence for its core energy metabolism or in vivo growth substrates is lacking. Here we show that N. gruberi trophozoites need oxygen for normal functioning and growth and that they furthermore shun both glucose and amino acids as growth substrates. Trophozoite growth depends mainly upon lipid oxidation via a mitochondrial branched respiratory chain, both ends of which require oxygen as final electron acceptor. Growing N. gruberi trophozoites thus have a strictly aerobic energy metabolism with a marked substrate preference for the oxidation of fatty acids. Analyses of N. fowleri genome data and comparison with those of N. gruberi indicate that N. fowleri has the same type of metabolism. Specialization to oxygen-dependent lipid breakdown represents a hitherto unprecedented metabolic strategy in protists.

biochemistry↗

bioRxiv2018

Count does not recover major events of gene flux in real biological data

In prokaryotes, known mechanisms of lateral gene transfer (transformation, transduction, conjugation and gene transfer agents) generate new combinations of genes among chromosomes during evolution. In eukaryotes, whose host lineage is descended from archaea, lateral gene transfer from organelles to the nucleus occurs at endosymbiotic events. Recent genome analyses studying gene distributions have uncovered evidence for sporadic, discontinuous events of gene transfer from bacteria to archaea during evolution. Other studies have used traditional birth-and-death phylogenetic models to investigate prokaryote genome evolution to claim that gene transfer to archaea was continuous during evolution, rather than involving occasional periodic mass gene influx events. Here we test the ability of Count, a birth-and-death based program, to recover known events of mass acquisition and differential loss using plastid genomes and eukaryotic protein families that were acquired from plastids. Count showed a strong bias towards reconstructed histories having gene acquisitions distributed uniformly across the tree. Sometimes as many as nine different acquisitions by plastid DNA were inferred for the same protein family. That is, Count recovered gradual and continuous lateral gene transfer among lineages, even when massive gains followed by gradual differential loss is the true evolutionary process that generated the gene distribution data.

evolutionary biology↗