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294 results for “photoreceptors”

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dryad28/100

Data from: Shifts in selective pressures on snake phototransduction genes associated with photoreceptor transmutation and dim-light ancestry

The visual systems of snakes are heavily modified relative to other squamates, a condition often thought to reflect their fossorial origins. Further modifications are seen in caenophidian snakes, where evolutionary transitions between rod and cone photoreceptors, termed photoreceptor transmutations, have occurred in many lineages. Little previous work, however, has focused on the molecular evolutionary underpinnings of these morphological changes. To address this, we sequenced seven snake eye transcriptomes and utilized new whole genome and targeted capture sequencing data. We used this data to analyze gene loss and shifts in selection pressures in phototransduction genes that may be associated with snake evolutionary origins and photoreceptor transmutation. We identified the surprising loss of rhodopsin kinase (GRK1), despite a low degree of gene loss overall and a lack of relaxed selection early during snake evolution. These results provide some of the first evolutionary genomic corroboration for a dim-light ancestor that lacks strong fossorial adaptations. Our results also indicate that snakes with photoreceptor transmutation experienced significantly different selection pressures from other reptiles. Significant positive selection was found primarily in cone-specific genes, but not rod-specific genes, contrary to our expectations. These results reveal potential molecular adaptations associated with photoreceptor transmutation, and also highlight unappreciated functional differences between rod- and cone-specific phototransduction proteins. This intriguing example of snake visual system evolution illustrates how the underlying molecular components of a complex system can be reshaped in response to changing selection pressures.

opencc-zeroDec 2017View details →

dryad28/100

Data from: Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns

Ferns are well known for their shade-dwelling habits. Their ability to thrive under low-light conditions has been linked to the evolution of a novel chimeric photoreceptor—neochrome—that fuses red-sensing phytochrome and blue-sensing phototropin modules into a single gene, thereby optimizing phototropic responses. Despite being implicated in facilitating the diversification of modern ferns, the origin of neochrome has remained a mystery. We present evidence for neochrome in hornworts (a bryophyte lineage) and demonstrate that ferns acquired neochrome from hornworts via horizontal gene transfer (HGT). Fern neochromes are nested within hornwort neochromes in our large-scale phylogenetic reconstructions of phototropin and phytochrome gene families. Divergence date estimates further support the HGT hypothesis, with fern and hornwort neochromes diverging 179 Mya, long after the split between the two plant lineages (at least 400 Mya). By analyzing the draft genome of the hornwort Anthoceros punctatus, we also discovered a previously unidentified phototropin gene that likely represents the ancestral lineage of the neochrome phototropin module. Thus, a neochrome originating in hornworts was transferred horizontally to ferns, where it may have played a significant role in the diversification of modern ferns.

opencc-zeroDec 2013View details →

dryad28/100

Data from: Evolutionary signatures of photoreceptor transmutation in geckos reveal potential adaptation and convergence with snakes

Most vertebrates use a combination of rod and cone photoreceptors to enable vision in conditions ranging from starlight to direct sunlight. Nocturnal geckos, however, have simplex retinas that contain only rods in terms of morphology and physiology, but these rods are thought to be derived from cones through an evolutionary process known as photoreceptor transmutation. To investigate this, we generated eye transcriptomes and analyzed patterns of phototransduction gene evolution in geckos in comparison to other reptiles. We confirm that geckos have lost several major components of the rod phototransduction pathway, including rod opsin (RH1), which we identified as a pseudogene in multiple genomes. We also identified a partial rod transducin transcript, but found no evidence of the protein in retinal sections. However, we find that geckos express several complete rod phototransduction transcripts in the eye, which may contribute to the rod-like physiology of nocturnal gecko photoreceptors. Finally, we found surprising evidence that even though photoreceptor transmutation evolved independently in geckos and snakes, they have experienced parallel shifts in selective constraint on phototransduction genes. These results implicate convergent adaptive change in the underlying molecular machinery of visual transduction, in addition to the more obvious changes to cellular morphology, during photoreceptor transmutation.

opencc-zeroJul 2019View details →

dryad28/100

Data from: Rab6 is required for multiple apical transport pathways but not the basolateral transport pathway in Drosophila photoreceptors

Polarized membrane trafficking is essential for the construction and maintenance of multiple plasma membrane domains of cells. Highly polarized Drosophila photoreceptors are an excellent model for studying polarized transport. A single cross-section of Drosophila retina contains many photoreceptors with 3 clearly differentiated plasma membrane domains: a rhabdomere, stalk, and basolateral membrane. Genome-wide high-throughput ethyl methanesulfonate screening followed by precise immunohistochemical analysis identified a mutant with a rare phenotype characterized by a loss of 2 apical transport pathways with normal basolateral transport. Rapid gene identification using whole-genome resequencing and single nucleotide polymorphism mapping identified a nonsense mutation of Rab6 responsible for the apical-specific transport deficiency. Detailed analysis of the trafficking of a major rhabdomere protein Rh1 using blue light-induced chromophore supply identified Rab6 as essential for Rh1 to exit the Golgi units. Rab6 is mostly distributed from the trans-Golgi network to a Golgi-associated Rab11-positive compartment that likely recycles endosomes or transport vesicles going to recycling endosomes. Furthermore, the Rab6 effector, Rich, is required for Rab6 recruitment in the trans-Golgi network. Moreover, a Rich null mutation phenocopies the Rab6 null mutant, indicating that Rich functions as a guanine nucleotide exchange factor for Rab6. The results collectively indicate that Rab6 and Rich are essential for the trans-Golgi network–recycling endosome transport of cargoes destined for 2 apical domains. However, basolateral cargos are sorted and exported from the trans-Golgi network in a Rab6-independent manner.

opencc-zeroDec 2015View details →

zenodo28/100

Supplementary material 1 from: Calderón-Rosete G, González-Barrios JA, Piña-Leyva C, Moreno-Sandoval HN, Lara-Lozano M, Rodríguez-Sosa L (2021) Transcriptional identification of genes light-interacting in the extraretinal photoreceptors of the crayfish Procambarus clarkii. ZooKeys 1072: 107-127. https://doi.org/10.3897/zookeys.1072.73075

Appendix S1, S2

opencc-zeroNov 2021View details →

zenodo28/100

Figure 1 from: Calderón-Rosete G, González-Barrios JA, Piña-Leyva C, Moreno-Sandoval HN, Lara-Lozano M, Rodríguez-Sosa L (2021) Transcriptional identification of genes light-interacting in the extraretinal photoreceptors of the crayfish Procambarus clarkii. ZooKeys 1072: 107-127. https://doi.org/10.3897/zookeys.1072.73075

Figure 1 Comparative alignments of opsins reported in the crayfish Procambarus clarkiiA long-wavelength-sensitive opsin (UniProtKB/Swiss-Prot: P35356.1; Hariyama et al. 1993); (GenBank: ALJ26467 1; Kingston and Cronin 2015); (Procl_ES_23_0; Manfrin et al. 2015) B short-wavelength-sensitive opsin (GenBank: ALJ26468.1; Kingston and Cronin 2015); (Procl_ES_11143_0; Manfrin et al. 2015)

opencc-by-4.0Nov 2021View details →

dryad28/100

Data from: Whole-body photoreceptor networks are independent of 'lenses' in brittle stars

Photoreception and vision are fundamental aspects of animal sensory biology and ecology, but important gaps remain in our understanding of these processes in many species. The colour-changing brittle star Ophiocoma wendtii is iconic in vision research, speculatively possessing a unique whole-body visual system that incorporates information from nerve bundles underlying thousands of crystalline 'microlenses'. The hypothesis that these form a sophisticated compound eye-like system regulated by chromatophore movement has been extensively reiterated, with consequent investigations into biomimetic optics and similar 'visual' structures in living and fossil taxa. However, no photoreceptors or visual behaviours have ever been identified. We present the first evidence of photoreceptor networks in three Ophiocoma species, both with and without microlenses and colour-changing behaviour. High-resolution microscopy, immunohistochemistry and synchrotron tomography demonstrate that putative photoreceptors cover the animals' oral, lateral, and aboral surfaces, but are absent at the hypothesised focal points of the microlenses. The structural optics of these crystal 'lenses' are an exaptation and do not fulfil any apparent visual role. This contradicts previous studies, yet the photoreceptor network in Ophiocoma appears even more widespread than previously anticipated, both taxonomically and anatomically.

opencc-zeroDec 2017View details →

zenodo28/100

Datasets of the article "QM calculations predict the energetics and infrared spectra of transient glutamine isomers in LOV photoreceptors"

Experimental time-resolved infrared spectra (light-minus-dark absorption difference) of EL222-WT in deuterated buffer (DATA), and evolution-associated difference spectra (EADS) arising from global kinetic analysis using a 3-components sequential model: singlet (1FMN*), triplet (3FMN*) and adduct (A390). These are the data used to prepare panels a) and c) of Figure 4 from the paper: Andrikopoulos, P. C.; Chaudhari, A.S.; Liu, Y.; Konold, P.E.; Kennis, J.T.M.; Schneider, B.; Fuertes, G. QM Calculations Predict the Energetics and Infrared Spectra of Transient Glutamine Isomers in LOV Photoreceptors. Phys. Chem. Chem. Phys., 2021, 23, 13934-13950. <a href="https://doi.org/10.1039/d1cp00447f">https://doi.org/10.1039/d1cp00447f</a>.

opencc-by-4.0Jun 2021View details →

dryad28/100