scholarly journals The evolution of early vertebrate photoreceptors

2009 ◽  
Vol 364 (1531) ◽  
pp. 2925-2940 ◽  
Author(s):  
Shaun P. Collin ◽  
Wayne L. Davies ◽  
Nathan S. Hart ◽  
David M. Hunt
Keyword(s):  
Common Ancestor ◽  
Sampling Strategy ◽  
Rods And Cones ◽  
Eye Evolution ◽  
Living Fossils ◽  
The Common ◽  
Early Vertebrates ◽  
Cartilaginous Fishes ◽  
Dim Light ◽  
Aquatic Landscape

Meeting the challenge of sampling an ancient aquatic landscape by the early vertebrates was crucial to their survival and would establish a retinal bauplan to be used by all subsequent vertebrate descendents. Image-forming eyes were under tremendous selection pressure and the ability to identify suitable prey and detect potential predators was thought to be one of the major drivers of speciation in the Early Cambrian. Based on the fossil record, we know that hagfishes, lampreys, holocephalans, elasmobranchs and lungfishes occupy critical stages in vertebrate evolution, having remained relatively unchanged over hundreds of millions of years. Now using extant representatives of these ‘living fossils’, we are able to piece together the evolution of vertebrate photoreception. While photoreception in hagfishes appears to be based on light detection and controlling circadian rhythms, rather than image formation, the photoreceptors of lampreys fall into five distinct classes and represent a critical stage in the dichotomy of rods and cones. At least four types of retinal cones sample the visual environment in lampreys mediating photopic (and potentially colour) vision, a sampling strategy retained by lungfishes, some modern teleosts, reptiles and birds. Trichromacy is retained in cartilaginous fishes (at least in batoids and holocephalans), where it is predicted that true scotopic (dim light) vision evolved in the common ancestor of all living gnathostomes. The capacity to discriminate colour and balance the tradeoff between resolution and sensitivity in the early vertebrates was an important driver of eye evolution, where many of the ocular features evolved were retained as vertebrates progressed on to land.

The Possible Common Origin of tRNA and 5S rRNA

1983 ◽  
Vol 38 (5-6) ◽  
pp. 501-504 ◽  
Author(s):  
Mária Ujhelyi
Keyword(s):  
Common Ancestor ◽  
Common Origin ◽  
5S Rrna ◽  
Mitochondrial Trna ◽  
Trna Molecule ◽  
The Common

Seryl tRNA (anticodon GCU) from mammalian mito­chondria shows in comparison to other mitochondrial tRNAs additional special features differing from the generalized tRNA model. When arranged in the tradi­tional cloverleaf form, eight bases fall within the TΨC loop, and the entire dihydrouridine loop is lacking. This seryl tRNA molecule is therefore shorter than other tRNAs. It was originally thought to represent a mito­chondrial analogon of 5 S rRNA and its precise classifica­tion is still disputed. The present studies suggest that this mitochondrial tRNA represents a fossil molecule which is related to the common ancestor of the present tRNA and 5 S rRNA molecules.

scholarly journals Role of the Digestive Gland in Ink Production in Four Species of Sea Hares: An Ultrastructural Comparison

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Jeffrey S. Prince ◽  
Paul Micah Johnson
Keyword(s):  
Digestive Gland ◽  
Common Ancestor ◽  
Aplysia Californica ◽  
Digestive Cell ◽  
Digestive Cells ◽  
Sea Hare ◽  
Red Algal ◽  
The Common ◽  
Algal Chloroplast

The ultrastructure of the digestive gland of several sea hare species that produce different colored ink (Aplysia californicaproduces purple ink,A. julianawhite ink,A. parvulaboth white and purple ink, whileDolabrifera dolabriferaproduces no ink at all) was compared to determine the digestive gland’s role in the diet-derived ink production process. Rhodoplast digestive cells and their digestive vacuoles, the site of digestion of red algal chloroplast (i.e., rhodoplast) inA. californica, were present and had a similar ultrastructure in all four species. Rhodoplast digestive cell vacuoles either contained a whole rhodoplast or fragments of one or were empty. These results suggest that the inability to produce colored ink in some sea hare species is not due to either an absence of appropriate digestive machinery, that is, rhodoplast digestive cells, or an apparent failure of rhodoplast digestive cells to function. These results also propose that the digestive gland structure described herein occurred early in sea hare evolution, at least in the common ancestor to the generaAplysiaandDolabrifera. Our data, however, do not support the hypothesis that the loss of purple inking is a synapomorphy of the white-ink-producing subgenusAplysia.

scholarly journals Sexual reproduction and genetic exchange in parasitic protists

Parasitology ◽  
2014 ◽  
Vol 142 (S1) ◽  
pp. S120-S127 ◽  
Author(s):  
GARETH D. WEEDALL ◽  
NEIL HALL
Keyword(s):  
Life Cycle ◽  
Genome Sequencing ◽  
Common Ancestor ◽  
Life Cycles ◽  
Animal Disease ◽  
Eukaryotic Evolution ◽  
Sequencing Technology ◽  
Parasite Reproduction ◽  
The Common ◽  
Higher Eukaryotes

SUMMARYA key part of the life cycle of an organism is reproduction. For a number of important protist parasites that cause human and animal disease, their sexuality has been a topic of debate for many years. Traditionally, protists were considered to be primitive relatives of the ‘higher’ eukaryotes, which may have diverged prior to the evolution of sex and to reproduce by binary fission. More recent views of eukaryotic evolution suggest that sex, and meiosis, evolved early, possibly in the common ancestor of all eukaryotes. However, detecting sex in these parasites is not straightforward. Recent advances, particularly in genome sequencing technology, have allowed new insights into parasite reproduction. Here, we review the evidence on reproduction in parasitic protists. We discuss protist reproduction in the light of parasitic life cycles and routes of transmission among hosts.

Diversity and Evolution of Mineralized Skeletal Tissues in Chondrichthyans

2021 ◽  
Vol 9 ◽  
Author(s):  
Fidji Berio ◽  
Morgane Broyon ◽  
Sébastien Enault ◽  
Nelly Pirot ◽  
Faviel A. López-Romero ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Phylogenetic Relationships ◽  
Current Knowledge ◽  
Neural Arch ◽  
Fossil Species ◽  
Fibrous Matrix ◽  
Cartilaginous Matrix ◽  
Mineralized Tissues ◽  
Early Vertebrates ◽  
Cartilaginous Fishes

The diversity of skeletal tissues in extant vertebrates includes mineralized and unmineralized structures made of bone, cartilage, or tissues of intermediate nature. This variability, together with the diverse nature of skeletal tissues in fossil species question the origin of skeletonization in early vertebrates. In particular, the study of skeletal tissues in cartilaginous fishes is currently mostly restrained to tessellated cartilage, a derived form of mineralized cartilage that evolved at the origin of this group. In this work, we describe the architectural and histological diversity of neural arch mineralization in cartilaginous fishes. The observed variations in the architecture include tessellated cartilage, with or without more massive sites of mineralization, and continuously mineralized neural arches devoid of tesserae. The histology of these various architectures always includes globular mineralization that takes place in the cartilaginous matrix. In many instances, the mineralized structures also include a fibrous component that seems to emerge from the perichondrium and they may display intermediate features, ranging from partly cartilaginous to mostly fibrous matrix, similar to fibrocartilage. Among these perichondrial mineralized tissues is also found, in few species, a lamellar arrangement of the mineralized extracellular matrix. The evolution of the mineralized tissues in cartilaginous fishes is discussed in light of current knowledge of their phylogenetic relationships.

Whole-genome analysis-based phylogeographic investigation of Streptococcus pneumoniae serotype 19A sequence type 320 isolates in Japan.

2021 ◽  
Author(s):  
Satoshi Nakano ◽  
Takao Fujisawa ◽  
Bin Chang ◽  
Yutaka Ito ◽  
Hideki Akeda ◽  
...  
Keyword(s):  
Common Ancestor ◽  
Sampling Bias ◽  
Health Concern ◽  
Recent Common Ancestor ◽  
Whole Genome ◽  
Whole Genome Analysis ◽  
Identification Rate ◽  
Most Recent Common Ancestor ◽  
The Common ◽  
The U.S

After the introduction of the seven-valent pneumococcal conjugate vaccine, the global spread of multidrug resistant serotype 19A-ST320 strains became a public health concern. In Japan, the main genotype of serotype 19A was ST3111, and the identification rate of ST320 was low. Although the isolates were sporadically detected in both adults and children, their origin remains unknown. Thus, by combining pneumococcal isolates collected in three nationwide pneumococcal surveillance studies conducted in Japan between 2008 and 2020, we analyzed 56 serotype 19A-ST320 isolates along with 931 global isolates, using whole-genome sequencing to uncover the transmission route of the globally distributed clone in Japan. The clone was frequently detected in Okinawa Prefecture, where the U.S. returned to Japan in 1972. Phylogenetic analysis demonstrated that the isolates from Japan were genetically related to those from the U.S.; therefore, the common ancestor may have originated in the U.S. In addition, Bayesian analysis suggested that the time to the most recent common ancestor of the isolates form Japan and the U.S. was approximately the 1990s to 2000, suggesting the possibility that the common ancestor could have already spread in the U.S. before the Taiwan 19F-14 isolate was first identified in a Taiwanese hospital in 1997. The phylogeographical analysis supported the transmission of the clone from the U.S. to Japan, but the analysis could be influenced by sampling bias. These results suggested the possibility that the serotype 19A-ST320 clone had already spread in the U.S. before being imported into Japan.

scholarly journals Comparing the folding landscapes of evolutionarily divergent procaspase-3

2022 ◽  
Author(s):  
Liqi Yao ◽  
Clay Clark
Keyword(s):  
Conformational Change ◽  
Common Ancestor ◽  
Folding Pathway ◽  
Free Energies ◽  
Folding Intermediates ◽  
Effector Caspases ◽  
The Common ◽  
Ph Dependent ◽  
Species Specific ◽  
Dimeric Intermediate

All caspases evolved from a common ancestor and subsequently developed into two general classes, inflammatory or apoptotic caspases. The caspase-hemoglobinase fold has been conserved throughout nearly one billion years of evolution and is utilized for both the monomeric and dimeric subfamilies of apoptotic caspases, called initiator and effector caspases, respectively. We compared the folding and assembly of procaspase-3b from zebrafish to that of human effector procaspases in order to examine the conservation of the folding landscape. Urea-induced equilibrium folding/unfolding of procaspase-3b showed a minimum three-state folding pathway, where the native dimer isomerizes to a partially folded dimeric intermediate, which then unfolds. A partially folded monomeric intermediate observed in the folding landscape of human procaspase-3 is not well-populated in zebrafish procaspase-3b. By comparing effector caspases from different species, we show that the effector procaspase dimer undergoes a pH-dependent conformational change, and that the conformational species in the folding landscape exhibit similar free energies. Together, the data show that the landscape for the caspase-hemoglobinase fold is conserved, yet it provides flexibility for species-specific stabilization or destabilization of folding intermediates resulting in changes in stability. The common pH-dependent conformational change in the native dimer, which yields an enzymatically inactive species, may provide an additional, albeit reversible, mechanism for controlling caspase activity in the cell.

scholarly journals Loss of plastid developmental genes coincides with a reversion to monoplastidy in hornworts

2022 ◽  
Author(s):  
Alexander Istvan MacLeod ◽  
Parth K Raval ◽  
Simon Stockhorst ◽  
Michael Knopp ◽  
Eftychios Frangedakis ◽  
...  
Keyword(s):  
Common Ancestor ◽  
Nuclear Division ◽  
Developmental Pathways ◽  
Ancestral State ◽  
Plastid Division ◽  
Plastid Development ◽  
State Reconstruction ◽  
Transcriptomic Data ◽  
The Common ◽  
Almost All

The first plastid evolved from an endosymbiotic cyanobacterium in the common ancestor of the Archaeplastida. The transformative steps from cyanobacterium to organelle included the transfer of control over developmental processes; a necessity for the host to orchestrate, for example, the fission of the organelle. The plastids of almost all embryophytes divide independent from nuclear division, leading to cells housing multiple plastids. Hornworts, however, are monoplastidic (or near-monoplastidic) and their photosynthetic organelles are a curious exception among embryophytes for reasons such as the occasional presence of pyrenoids. Here we screened genomic and transcriptomic data of eleven hornworts for components of plastid developmental pathways. We find intriguing differences among hornworts and specifically highlight that pathway components involved in regulating plastid development and biogenesis were differentially lost in this group of bryophytes. In combination with ancestral state reconstruction, our data suggest that hornworts have reverted back to a monoplastidic phenotype due to the combined loss of two plastid division-associated genes: ARC3 and FtsZ2.

scholarly journals Introgression from Gorilla caused the Human-Chimpanzee split

2018 ◽  
Author(s):  
Johan Nygren
Keyword(s):  
Common Ancestor ◽  
Nuclear Genome ◽  
Genome Project ◽  
Lineage Sorting ◽  
Chromosome 5 ◽  
Speciation Model ◽  
Introgression Event ◽  
The Common

ABSTRACT: The Gorilla Genome Project (Scally, 2012) showed that 30% of the gorilla genome introgressed into the ancestor of humans and chimpanzees, and that the two species diverged through lineage sorting with 15% ending up in Pan and another 15% in Homo. That introgression is the Pan-Homo split, hybridization, which led to speciation as the new hybrid lineages became reproductively isolated from one another. The NUMT on chromosome 5 (“ps5”) (Popadin, 2017) fits perfectly with the introgression speciation model, it was formed from mtDNA that had diverged from the common ancestor of Pan-Homo for 1.8 Myr at the time of insertion into the nuclear genome, and originated in the Gorilla lineage. The ps5 pseudogene was transferred to Pan and Homo during the introgression event that led to the Pan-Homo split, 6 million years ago.

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