Evolutionary adaptation of visual pigments in geckos for their photic environment

家の守り神「ヤモリ」が夜でも色を見分けられるのはなぜ --ヤモリが持つ特殊な色覚能力の分子メカニズムを解明--. 京都大学プレスリリース. 2021-10-04.Vertebrates generally have a single type of rod for scotopic vision and multiple types of cones for photopic vision. Noteworthily, nocturnal geckos transmuted ancestral photoreceptor cells into rods containing not rhodopsin but cone pigments, and, subsequently, diurnal geckos retransmuted these rods into cones containing cone pigments. High sensitivity of scotopic vision is underlain by the rod’s low background noise, which originated from a much lower spontaneous activation rate of rhodopsin than of cone pigments. Here, we revealed that nocturnal gecko cone pigments decreased their spontaneous activation rates to mimic rhodopsin, whereas diurnal gecko cone pigments recovered high rates similar to those of typical cone pigments. We also identified amino acid residues responsible for the alterations of the spontaneous activation rates. Therefore, we concluded that the switch between diurnality and nocturnality in geckos required not only morphological transmutation of photoreceptors but also adjustment of the spontaneous activation rates of visual pigments

Palmitate induces reactive oxygen species production and β-cell dysfunction by activating nicotinamide adenine dinucleotide phosphate oxidase through Src signaling.

[Aims/Introduction]Chronic hyperlipidemia impairs pancreatic β-cell function, referred to as lipotoxicity. We have reported an important role of endogenous reactive oxygen species (ROS) overproduction by activation of Src, a non-receptor tyrosine kinase, in impaired glucose-induced insulin secretion (GIIS) from diabetic rat islets. In the present study, we investigated the role of ROS production by Src signaling in palmitate-induced dysfunction of β-cells. [Materials and Methods]After rat insulinoma INS-1D cells were exposed to 0.6 mmol/L palmitate for 24 h (palmitate exposure); GIIS, ROS production and nicotinamide adenine dinucleotide phosphate oxidase (NOX) activity were examined with or without exposure to10 μmol/L 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), a Src inhibitior, for 30 or 60 min. [Results]Exposure to PP2 recovered impaired GIIS and decreased ROS overproduction as a result of palmitate exposure. Palmitate exposure increased activity of NOX and protein levels of NOX2, a pathological ROS source in β-cells. Palmitate exposure increased the protein level of p47phox, a regulatory protein of NOX2, in membrane fraction compared with control, which was reduced by PP2. Transfection of small interfering ribonucleic acid of p47phox suppressed the augmented p47phox protein level in membrane fraction, decreased augmented ROS production and increased impaired GΙIS by palmitate exposure. In addition, exposure to PP2 ameliorated impaired GIIS and decreased ROS production in isolated islets of KK-Ay mice, an obese diabetic model with hyperlipidemia. [Conclusions]Activation of NOX through Src signaling plays an important role in ROS overproduction and impaired GΙIS caused by chronic exposure to palmitate, suggesting a lipotoxic mechanism of β-cell dysfunction of obese mice

Spatio-temporal marine conservation planning to support high-latitude coral range expansion under climate change

Aim: Increasing sea-surface temperatures (SST) have resulted in poleward range expansions of scleractinian corals and declines in their core ranges. These changes may provide management opportunities for the long-term persistence of corals, but spatial prioritization rarely considers and anticipates these changes. We developed a spatio-temporal conservation plan that accommodates future coral range expansions based on projections of future SST. Our spatial planning approach is particularly useful in places with limited information about species distributions. Our aims were to (1) identify areas that consistently remain important for conservation through time and (2) determine the differences between priorities for conservation that account for potential coral range expansions and those that ignore them. Location: Japan. Methods: We developed spatial planning approaches using predicted coral habitat distributions for current conditions, the near future and the distant future. Using the Marxan conservation planning software, we designed conservation plans for scenarios that incorporated different types of spatial and temporal connections. Spatial connections are physical connections between adjacent and nearby areas, whereas temporal connections connect planning areas throughout time. Results: We found that protecting areas important for current and future coral habitat distributions is possible by prioritizing places that are consistently important through time. A spatially and temporally cohesive plan was accomplished with only a 14% increase in the overall reserve system costs, compared with reserve systems ignoring future coral habitat distributions. The attributes of priority areas (e.g. locations, outside boundary length and size) were substantially different when we varied the types of connections. Main conclusions: This study demonstrated that areas with highest conservation priority now will not necessarily be optimal when planning for future change, such as coral range expansions. Furthermore, we showed that incorporating spatio-temporal connections into spatial prioritization achieves objectives of simultaneously conserving corals in the current climate and facilitating their expansions as SST rises

Pinopsin evolved as the ancestral dim-light visual opsin in vertebrates

脊椎動物の視覚進化モデルを修正 --暗所視と色覚はどっちが先か--. 京都大学プレスリリース. 2018-10-02.Pinopsin is the opsin most closely related to vertebrate visual pigments on the phylogenetic tree. This opsin has been discovered among many vertebrates, except mammals and teleosts, and was thought to exclusively function in their brain for extraocular photoreception. Here, we show the possibility that pinopsin also contributes to scotopic vision in some vertebrate species. Pinopsin is distributed in the retina of non-teleost fishes and frogs, especially in their rod photoreceptor cells, in addition to their brain. Moreover, the retinal chromophore of pinopsin exhibits a thermal isomerization rate considerably lower than those of cone visual pigments, but comparable to that of rhodopsin. Therefore, pinopsin can function as a rhodopsin-like visual pigment in the retinas of these lower vertebrates. Since pinopsin diversified before the branching of rhodopsin on the phylogenetic tree, two-step adaptation to scotopic vision would have occurred through the independent acquisition of pinopsin and rhodopsin by the vertebrate lineage

Synthesis of (3S,3′S)- and meso-Stereoisomers of Alloxanthin and Determination of Absolute Configuration of Alloxanthin Isolated from Aquatic Animals

In order to determine the absolute configuration of naturally occurring alloxanthin, a HPLC analytical method for three stereoisomers 1a–c was established by using a chiral column. Two authentic samples, (3S,3′S)- and meso-stereoisomers 1b and 1c, were chemically synthesized according to the method previously developed for (3R,3′R)-alloxanthin (1a). Application of this method to various alloxanthin specimens of aquatic animals demonstrated that those isolated from shellfishes, tunicates, and crucian carp are identical with (3R,3′R)-stereoisomer 1a, and unexpectedly those from lake shrimp, catfish, biwa goby, and biwa trout are mixtures of three stereoisomers of 1a–c

<Original Papers>Structure analysis of BasS and BasR in rice seedling blight pathogen Burkholderia plantarii

Burkholderia plantani is a plant pathogen causing rice seedling blight. It produces tropolone, the disease causing substance. To elucidate and understand molecular mechanisms of the pathogenesis, we analyzed the genome of B. plantarii. In this study, we focused on two component system, in prokaryotic signal transduction. This system is basically composed of a histidine kinase (HK, sensor) residing in the inner membrane and a cognate response regulator (RR) in the cytoplasm. Here, BasS, a histidine kinase (HK, sensor) and BasR, a response regulator (RR) in this strain, were structurally analysed, showing these are tandemely ordered. Phylogenetic analysis of these prodcuts were also analysed. Construction of plasmids for gene disruption of these genes, basS and basR was also carried out, in terms of future study approach in reverse genetics. Obtaining mutants by transformation will be useful for understanding the relationships between pathogenesis and function of these genes

Projected coral bleaching in response to future sea surface temperature rises and the uncertainties among climate models

We quantitatively evaluated the effects of rising sea surface temperature (SST) on coral bleaching and the uncertainties resulting from differences in global warming projections. To do so, we used monthly SSTs in the twenty-first century obtained from 23 climate models under the A1B scenario (from the Special Report on Emissions Scenarios) and SST-based indices for coral bleaching. All of the projections indicated that severe bleaching or death of corals will be common and severe in wide areas of the tropical and subtropical oceans by the middle of this century. However, decadal oscillation could modify the exact timing by around +/- 10 years. Such projections are important for conserving marine biodiversity and designing future strategies to avoid tropical and subtropical coral extinction. To obtain more reliable projections and reduce uncertainties, climate models should be improved by using higher spatiotemporal resolutions, and more realistic biological indices should be embedded into existing models

Projection and uncertainty of the poleward range expansion of coral habitats in response to sea surface temperature warming: A multiple climate model study

Using projected monthly mean sea surface tem-perature (SST) in the 21st century obtained by multiple climate models and SST-based indices for the poleward range expansions of three types of coral habitats, we quantitatively evaluated the effects of SST warming on potential northern limit of coral habitats in seas close to Japan and their uncertainty in the global warming pro-jections. The uncertainty in the timing of temperate coral community formation due to global warming was no less than 30 years, with a modulation of ±10 years due to decadal climate variability. Tropical-subtropical and tem-perate coral communities and coral occurrence in seas close to Japan were predicted to shift poleward by a few hundred kilometers by the end of the 21st century. The average estimated speeds of the shifts were 1, 2, and 4 km/year for the tropical-subtropical coral community, temper-ate coral community, and coral occurrence, respectively. The simulated speeds were relatively slower than those previously observed (up to 14 km/year; Yamano et al. 2011), indicating that there are time lags between the new recruitment of coral colonies and the establishment of coral communities. Hence, monitoring of coral dynamics in response to SST warming is required. Collaboration between monitoring and modeling would enhance the reliability of future projections of changes in coral ha-bitats. Such projections are important for conserving marine biodiversity and developing plans for human societies to adapt to global warming

Total Synthesis of Loroxanthin

The first total synthesis of loroxanthin (1) was accomplished by Horner-Wadsworth-Emmons reaction of C25-apocarotenal 8 having a silyl-protected 19-hydroxy moiety with C15-phosphonate 25 bearing a silyl-protected 3-hydroxy-&epsilon;-end group. Preparation of apocarotenal 8 was achieved via Stille coupling reaction of alkenyl iodide 10 with alkenyl stananne 9, whereas phosphonate 25 was prepared through treatment of ally alcohol 23 with triethyl phosphite and ZnI2. The ally alcohol 23 was derived from the known (3R,6R)-3-hydroxy C15-aldehyde 20, which was obtained by direct optical resolution of racemate 20 using a semi-preparative chiral HPLC column