The outer segments (OS) of rod and cone photoreceptor cells are specialized sensory cilia that contain hundreds of opsin-loaded stacked membrane disks that enable phototransduction. The biogenesis of these disks is initiated at the OS base, but the driving force has been debated. Here, we studied the function of the...

The atypical trichromatic cyanobacterial phytochrome NpTP1 from Nostoc punctiforme ATCC 29133 is a linear tetrapyrrole (bilin)-binding photoreceptor protein that possesses tandem-cysteine residues responsible for shifting its light-sensing maximum to the violet spectral region. Using bioinformatics and phylogenetic analyses, here we established that tandem-cysteine cyanobacterial phytochromes (TCCPs) compose a well-supported monophyletic phytochrome lineage distinct from prototypical red/far-red cyanobacterial phytochromes. To investigate the light-sensing diversity of this family, we compared the spectroscopic properties of NpTP1 (here renamed NpTCCP) with those of three phylogenetically diverged TCCPs identified in the draft genomes of Tolypothrix sp. PCC7910, Scytonema sp. PCC10023, and Gloeocapsa sp. PCC7513. Recombinant photosensory core modules of ToTCCP, ScTCCP, and GlTCCP exhibited violet-blue–absorbing dark-states consistent with dual thioether-linked phycocyanobilin (PCB) chromophores. Photoexcitation generated singly-linked photoproduct mixtures with variable ratios of yellow-orange and red-absorbing species. The photoproduct ratio was strongly influenced by pH and by mutagenesis of TCCP- and phytochrome-specific signature residues. Our experiments support the conclusion that both photoproduct species possess protonated 15E bilin chromophores, but differ in the ionization state of the noncanonical “second” cysteine sulfhydryl group. We found that the ionization state of this and other residues influences subsequent conformational change and downstream signal transmission. We also show that tandem-cysteine phytochromes present in eukaryotes possess similar amino acid substitutions within their chromophore-binding pocket, which tune their spectral properties in an analogous fashion. Taken together, our findings provide a roadmap for tailoring the wavelength specificity of plant phytochromes to optimize plant performance in diverse natural and artificial light environments.

Arrestin-1 is the arrestin family member responsible for inactivation of the G protein–coupled receptor rhodopsin in photoreceptors. Arrestin-1 is also well-known to interact with additional protein partners and to affect other signaling cascades beyond phototransduction. In this study, we investigated one of these alternative arrestin-1 binding partners, the glycolysis enzyme enolase-1, to map the molecular contact sites between these two proteins and investigate how the binding of arrestin-1 affects the catalytic activity of enolase-1. Using fluorescence quench protection of strategically placed fluorophores on the arrestin-1 surface, we observed that arrestin-1 primarily engages enolase-1 along a surface that is opposite of the side of arrestin-1 that binds photoactivated rhodopsin. Using this information, we developed a molecular model of the arrestin-1–enolase-1 complex, which was validated by targeted substitutions of charge-pair interactions. Finally, we identified the likely source of arrestin's modulation of enolase-1 catalysis, showing that selective substitution of two amino acids in arrestin-1 can completely remove its effect on enolase-1 activity while still remaining bound to enolase-1. These findings open up opportunities for examining the functional effects of arrestin-1 on enolase-1 activity in photoreceptors and their surrounding cells.

Cone photoreceptors in the retina enable vision over a wide range of light intensities. However, the processes enabling cone vision in bright light (i.e. photopic vision) are not adequately understood. Chromophore regeneration of cone photopigments may require the retinal pigment epithelium (RPE) and/or retinal Müller glia. In the RPE, isomerization of all-trans-retinyl esters to 11-cis-retinol is mediated by the retinoid isomerohydrolase Rpe65. A putative alternative retinoid isomerase, dihydroceramide desaturase-1 (DES1), is expressed in RPE and Müller cells. The retinol-isomerase activities of Rpe65 and Des1 are inhibited by emixustat and fenretinide, respectively. Here, we tested the effects of these visual cycle inhibitors on immediate, early, and late phases of cone photopic vision. In zebrafish larvae raised under cyclic light conditions, fenretinide impaired late cone photopic vision, while the emixustat-treated zebrafish unexpectedly had normal vision. In contrast, emixustat-treated larvae raised under extensive dark-adaptation displayed significantly attenuated immediate photopic vision concomitant with significantly reduced 11-cis-retinaldehyde (11cRAL). Following 30 min of light, early photopic vision was recovered, despite 11cRAL levels remaining significantly reduced. Defects in immediate cone photopic vision were rescued in emixustat- or fenretinide-treated larvae following exogenous 9-cis-retinaldehyde supplementation. Genetic knockout of Des1 (degs1) or retinaldehyde-binding protein 1b (rlbp1b) did not eliminate photopic vision in zebrafish. Our findings define molecular and temporal requirements of the nonphotopic or photopic visual cycles for mediating vision in bright light.

Microbial mat communities are associated with extensive (~700 km²) and morphologically variable carbonate structures, termed microbialites, in the hypersaline Great Salt Lake (GSL), Utah. However, whether the composition of GSL mat communities covaries with microbialite morphology and lake environment is unknown. Moreover, the potential adaptations that allow the establishment of these extensive mat communities at high salinity (14% to 17% total salts) are poorly understood. To address these questions, microbial mats were sampled from seven locations in the south arm of GSL representing different lake environments and microbialite morphologies. Despite the morphological differences, microbialite-associated mats were taxonomically similar and were dominated by the cyanobacterium Euhalothece and several heterotrophic bacteria. Metagenomic sequencing of a representative mat revealed Euhalothece and subdominant Thiohalocapsa populations that harbor the Calvin cycle and nitrogenase, suggesting they supply fixed carbon and nitrogen to heterotrophic bacteria. Fifteen of the next sixteen most abundant taxa are inferred to be aerobic heterotrophs and, surprisingly, harbor reaction center, rhodopsin, and/or bacteriochlorophyll biosynthesis proteins, suggesting aerobic photoheterotrophic (APH) capabilities. Importantly, proteins involved in APH are enriched in the GSL community relative to that in microbialite mat communities from lower salinity environments. These findings indicate that the ability to integrate light into energy metabolism is a key adaptation allowing for robust mat development in the hypersaline GSL.

IMPORTANCE The earliest evidence of life on Earth is from organosedimentary structures, termed microbialites, preserved in 3.481-billion-year-old (Ga) rocks. Phototrophic microbial mats form in association with an ~700-km² expanse of morphologically diverse microbialites in the hypersaline Great Salt Lake (GSL), Utah. Here, we show taxonomically similar microbial mat communities are associated with morphologically diverse microbialites across the lake. Metagenomic sequencing reveals an abundance and diversity of autotrophic and heterotrophic taxa capable of harvesting light energy to drive metabolism. The unexpected abundance of and diversity in the mechanisms of harvesting light energy observed in GSL mat populations likely function to minimize niche overlap among coinhabiting taxa, provide a mechanism(s) to increase energy yield and osmotic balance during salt stress, and enhance fitness. Together, these physiological benefits promote the formation of robust mats that, in turn, influence the formation of morphologically diverse microbialite structures that can be imprinted in the rock record.

This week we’re old and complainy. Chris is down on the Switch. Then he’s down on FFXI’s endgame loot. Then he’s down on Pokémon’s postgame....

The newly-remastered images show the icy surface of Europa, the sixth of Jupiter’s moons and the fourth largest, in enhanced color. All three high-resolution images were captured along the same longitude of Europa as NASA’s Galileo spacecraft flew by on September 26, 1998, in the eighth of the spacecraft’s 11 targeted flybys of the icy [...]

Sania Mirza took to social media to post a picture with her son Izhaan.

Vanessa Bryant, the widow of late NBA star Kobe Bryant, filed a legal claim Friday against the Los Angeles County Sheriff’s Department over graphic photos that deputies allegedly took and shared of the helicopter crash scene where her husband, 13-year-old daughter, Gigi, and seven others were killed in late January.

Marine biologist Cristina Mittermeier discovered that visual storytelling, rather than data sets, allowed her to be a better advocate for the ocean

Images show streets and roads lying deserted as today marked one month since lockdown measures were put in place in the UK to curb the spread of Covid-19.

Adorable new photographs of Prince Louis taken by his mother Kate have been released ahead of his first birthday.

Prince Louis has shown his support for the NHS by making a rainbow poster for a series of photographs to mark his second birthday.

The Prince of Wales has shared a photo of himself tenderly hugging his grandson Prince Louis to mark the royal toddler's second birthday.

An English bulldog nicknamed "Big Poppa" has found internet fame after his owner posted a picture of him looking forlorn during the coronavirus lockdown.

As speculation continues over Kim Jong Un's health, satellite imagery has found a train likely belonging to the North Korean leader, a website specialising in studies of the country revealed.

Police have released a photo of a car believed to have been driven by the killers of a key worker.

Princess Charlotte's fifth birthday has been marked by the release of photographs showing the young royal helping to load a van with food and delivering meals for those in need.

The Duchess of Cambridge has launched a landmark photographic project to capture the "spirit of the nation" during the coronavirus outbreak.

The mundanity of coronavirus lockdown life is being celebrated in a photography exhibition to raise money for frontline workers.

A solar-driven hydrogen-producing machine that makes more copies of itself.

Unesco has named the capital of Rajasthan, India, a world heritage site, partly for its jewellery and artisanal traditions, which continue to thrive on one of its main commercial streets

‘Sir, want precious stones?” a man asks me, quietly. I am on the Johari Bazaar, one of Jaipur’s most notable thoroughfares, a straight colonnade screened above by the facades of adjoining houses. Everything is painted orange, terracotta and burnt pink. The man wears white shalwar kameez, and an air of indifference. He unfolds white paper, revealing colourful stones. “Emeralds, sapphires, rubies …” he says. He is among one of several groups of men gathered in this area; they’re local dealers, discussing prices. The avenue, whose name means gem shop road, is lined with dozens of shops displaying magnificent necklaces, bracelets and rings.

On a 9,288km journey inspired by the centennial anniversary of the railway’s completion in 1916, photographer Annie Ling captures life onboard the Trans-Siberian Railway, and beyond the carriage window

On a climbing trip in Australia – to the rock formations below Mount Wellington near Hobart – Murdo MacLeod gets more drama than he bargained for

Climbing guide John Fischer

Amid the historic quarter’s busy streets, a thousand workshops maintain centuries-old craftmaking traditions. These workers’ ancient skills are celebrated in a new exhibition at London’s Royal Geographical Society

“Whatever manufactured items there are in the world,” wrote the Ottoman traveller Evliya Çelebi in 1671, “the poor of Cairo get hold of them, set them out and trade in them.” Nearly 350 years later, this tradition lives on in al-Darb al-Ahmar. This neighbourhood of 100,000 people, south-east of central Cairo, is said to be home to a thousand workshops. The place teems with artisans crafting everything from tents, books, boxes and brass lanterns to glass bowls and silk carpets.

A supermoon happens when the moon reaches the closest point to Earth in its 27-day orbit and it happens to be full, which usually occurs once a year. We asked you to share your shots of April’s lunar spectacular. Here’s a selection of our favourites

"I just always want to reiterate the spiders are our friends, and this isn't a dangerous spider," said Royal B.C. Museum entomologist Claudia Copley.

Imaging specialist produces clearest pictures yet from dramatic Nasa mission

Comet had prompted excitement as astronomers expected it to be visible to the naked eye – but it has since broken up and is getting dimmer

Exes Demi Moore and Bruce Willis’ extended family struck a pose for the new Instagram photo, but with Bruce’s wife Emma and their two daughters missing. Emma and the girls recently joined Bruce in Demi’s Idaho home, just in time to celebrate Evelyn’s 6th birthday. Demi shared a snap with Bruce, their three girls, and […]

The post Bruce Willis’ Wife Emma And Their Two Daughters Are Missing From The Family Photo appeared first on Chart Attack.

Together with Britain's National Portrait Gallery, Duchess Kate is seeking touching photos that portray the country during the coronavirus pandemic.

Bethenny Frankel is wishing her daughter Bryn a very happy 10th birthday. The former Real Housewives of New York star marked the pre-teen's birthday by sharing a rare few photos, one...

Adele posted a rare photo of herself to celebrate her birthday, unveiling a dramatically altered appearance.

Starting Monday, “park ambassadors” will be stationed at Ottawa’s busiest parks to provide information about what's permitted under pandemic rules.

TV presenter, wife Stephanie and their daughters played a game of Murder Mystery

The singer said their post had been badly timed

Gigi and Bella Hadid have posed for a photoshoot at the family farm they're isolating in

What happens in Vegas stays in Vegas - but the pictures will make it to Instagram

The overall winner will be announced in June

The competition has officially launched for 2020 and wants you to send in your funny pet picture

With permission, of course

It's been 75 years since Winston Churchill announced the war in Europe was over

"All of my work has been cancelled [because of the crisis] and I was just missing shooting people and thought it would be a nice way for the community to come together and have a memory of this time.

Bethenny Frankel is wishing her daughter Bryn a very happy 10th birthday. The former Real Housewives of New York star marked the pre-teen's birthday by sharing a rare few photos, one...

The German Society for Nature Photography (GDT) has selected its Nature Photographer of the Year 2020.

The winning image is part of a series of photographs taken in Dortmund’s north by Peter Lindel. Compared with many international nature photography hot spots, this region has little to offer. Lindel spent a lot of time and blood, sweat and tears working on this project on his doorstep. It is a beautiful statement about the long-term exploration of a single species and region.