Biology subjects

Prakash, V.

Publications and source records attributed to Prakash, V..

6 recordsLinked to original sources

bioRxiv2025

Aggregation of the constitutively active K296E rhodopsin mutant contributes to retinal degeneration

A K296E mutation in rhodopsin causes autosomal dominant retinitis pigmentosa, a progressive retinal degenerative disease. Early in vitro characterizations of this mutation studied on a bovine rhodopsin background indicated that the mutation causes the receptor to be constitutively active. This molecular defect has been the primary focus when considering the pathogenic mechanism of the mutation. Knockin mice expressing the K296E rhodopsin mutant were generated and characterized to better understand the pathogenic mechanism of the mutation. Knockin mice exhibited progressive retinal degeneration characteristic of retinitis pigmentosa. The K296E rhodopsin mutant mislocalized in photoreceptor cells and, surprisingly, appeared to aggregate, as indicated by the dye PROTEOSTAT, which binds protein aggregates. The propensity of the K296E rhodopsin mutant to aggregate was tested and confirmed in vitro but was dependent on the species background of rhodopsin. The K296E mutation on either murine or human rhodopsin backgrounds exhibited similar propensities to aggregate. The same mutation on a bovine rhodopsin background, however, exhibited a lower propensity to aggregate, indicating this species background does not adequately model the effects of the K296E mutation. In contrast to previous expectations, we demonstrate here that aggregation of the K296E rhodopsin mutant can promote photoreceptor cell loss.

neuroscience↗

bioRxiv2023

Spatial patterns in the diet of Gyps vultures in India and their implications for conservation

Dietary analyses are particularly useful for developing conservation programmes for species threatened by resource depletion, poisoning and environmental pollution. Gyps vultures in South Asia represent one such case, having undergone a population collapse caused by feeding on carcasses of cattle treated with the non-steroidal anti-inflammatory drug diclofenac. Following a ban on the veterinary use of diclofenac, populations of vultures remain low and mostly concentrated near protected areas. Understanding the role of protected areas in the recovery of these critically endangered species requires analyses of spatial variation in their diet. We used faecal metabarcoding to investigate the spatial variation in the diet of Gyps vultures across four landscapes from sites located inside and outside protected areas. We collected faecal 642 samples, of which 419 yielded adequate molecular data to identify the vulture species and 30 molecular operational taxonomic units corresponding to at least 28 diet species. The diet was dominated by large ungulates and varied across landscapes, protection status and vulture species, with the observed variation largely explained by differential intake of wild and domestic species. Domestic livestock was present in >95% of the samples from central, west and north India, but 77% of the samples had only wild species in south India. This variation was explained by livestock density within 100 km radius of the sampling site. Our results imply that protected areas may not offer a respite from possibility of diclofenac-poisoning across most parts of the country and efforts should continue unabated to remove nephrotoxic drugs from veterinary use.

ecology↗

bioRxiv2023

Experimental safety testing confirms that the NSAID nimesulide is toxic to Gyps vultures in India

Population declines of Gyps vultures throughout South Asia were caused by unintentional poisoning by the NSAID diclofenac, which was subsequently banned. However, other vulture-toxic NSAIDs are available, including nimesulide, which, in experiments carried out in South Africa, was shown to be toxic to Gyps vultures. We report on safety-testing of nimesulide carried out on Himalayan Griffons G. himalayensis. We gave two vultures a dose of nimesulide by oral gavage at the maximum level of exposure, with two controls dosed with benzyl alcohol. In the two tested birds, plasma nimesulide concentrations peaked after six hours, while serum uric acid concentrations increased steadily up until 24 hours post-treatment, after which both birds died, displaying severe visceral gout. The control birds showed no adverse clinical or biochemical signs. We confirm that nimesulide is toxic to Gyps vultures. Veterinary use of nimesulide should be banned in all Gyps vulture range countries in the region.

pharmacology and toxicology↗

bioRxiv2022

The potyviral protein 6K2 from Turnip mosaic virus increases plant resilience to drought

Drought is a major cause of yield loss for crops worldwide. Climate change is predicted to increase global crop losses due to drought through rising temperature and decreased water availability. Virus infection can increase drought tolerance of infected plants compared to non-infected plants; however, the mechanisms mediating virus-induced drought tolerance remain unclear. In this study, we demonstrate Turnip mosaic virus (TuMV) infection increases Arabidopsis thaliana survival under drought compared to uninfected plants. To determine if specific TuMV proteins mediate drought tolerance, we cloned the coding sequence for each of the major viral proteins and generated transgenic A. thaliana that constitutively express each protein. Three TuMV proteins, 6K1, 6K2, and NIa-Pro, enhanced drought tolerance of A. thaliana when expressed constitutively in plants compared to controls. Expression of 6K2 also increased plant biomass relative to controls, but had no impact on root biomass, trichome numbers, or on the number of stomata. While drought induced transcripts related to abscisic acid (ABA) biosynthesis and ABA levels in control plants, compared to under well-watered conditions, there were no changes in ABA or related transcripts in plants expressing 6K2 under drought conditions compared to well-watered. 6K2 expression also conveyed drought tolerance in another host plant, Nicotiana benthamiana, when expressed using a virus over expression construct derived from Foxtail mosaic virus (FoMV). Although the exact mechanisms are still unknown, these results suggest 6K2-induced drought tolerance is ABA-independent and that plant viruses may represent novel sources of drought tolerance for crop plants.

plant biology↗

bioRxiv2019

Metabarcoding for parallel identification of species, sex and diet: an application to the conservation of globally-threatened Gyps vultures

An understanding of the factors affecting the diet composition of critically endangered Gyps vultures in the Indian subcontinent has important applications to the design of effective conservation strategies. After suffering a massive decline (~99%) in numbers caused by veterinary use of the nephrotoxic drug diclofenac, vultures now persist in very low numbers, mostly concentrated within or near National Parks. This spatial association might be attributed to the availability of wild ungulate carcasses free from toxic veterinary drugs. Hence, quantification of vulture diets and the factors affecting them is critical to test this hypothesis. Here, we describe and validate a robust \"field-to-benchtop-to-desktop\" metabarcoding workflow for assessing the species- and sex-specific diet of these obligate scavengers from non-invasively collected faecal samples. Seven metabarcodes targeting mitochondrial and nuclear genes were used to simultaneously determine the vulture species identity, sex and species consumed. The amplicons were sequenced using an Illumina Miseq platform. We included controls and three replicates per sample to establish a series of non-arbitrary thresholds to filter the sequence data and eliminate cross-contamination, PCR/sequencing errors and false positives. Using this strategy enabled identification of species and sex for all samples. Diet species-specific sequences could be identified with high taxonomic resolution for 93% of samples. Out of the seven metabarcodes, just four were sufficient to meet the objectives. From this preliminary analysis, domestic livestock seem to be the most frequently consumed diet item across samples from inside and outside protected habitats. Our method provides a rapid and reliable tool for describing large-scale variation in consumption of domestic versus wild species in the diet of these species, paving the way for a better understanding of the role protected areas play in persistence and recovery of the remaining Gyps vulture populations in the wild.

genetics↗

bioRxiv2019

Motility induced fracture reveals a ductile to brittle crossover in the epithelial tissues of a simple animal

Animals are characterized by their movement, and their tissues are continuously subjected to dynamic force loading while they crawl, walk, run or swim1. Tissue mechanics fundamentally determine the ecological niches that can be endured by a living organism2. While epithelial tissues provide an important barrier function in animals, they are subjected to extreme strains during day to day physiological activities, such as breathing1, feeding3, and defense response4. How-ever, failure or inability to withstand to these extreme strains can result in epithelial fractures5, 6 and associated diseases7, 8. From a materials science perspective, how properties of living cells and their interactions prescribe larger scale tissue rheology and adaptive response in dynamic force landscapes remains an important frontier9. Motivated by pushing tissues to the limits of their integrity, we carry out a multi-modal study of a simple yet highly dynamic organism, the Trichoplax Adhaerens10-12, across four orders of magnitude in length (1 {micro}m to 10 mm), and six orders in time (0.1 sec to 10 hours). We report the discovery of abrupt, bulk epithelial tissue fractures ([~]10 sec) induced by the organisms own motility. Coupled with rapid healing ([~]10 min), this discovery accounts for dramatic shape change and physiological asexual division in this early-divergent metazoan. We generalize our understanding of this phenomena by codifying it in a heuristic model, highlighting the fundamental questions underlying the debonding/bonding criterion in a soft-active-living material by evoking the concept of an epithelial alloy. Using a suite of quantitative experimental and numerical techniques, we demonstrate a force-driven ductile to brittle material transition governing the morphodynamics of tissues pushed to the edge of rupture. This work contributes to an important discussion at the core of developmental biology13-17, with important applications to an emerging paradigm in materials and tissue engineering5, 18-20, wound healing and medicine8, 21, 22.

biophysics↗