Biology subjects

Purohit, V.

Publications and source records attributed to Purohit, V..

4 recordsLinked to original sources

bioRxiv2026

Physiological Characterization under the Influence of Drought Stress and Salicylic Acid in Valeriana wallichii DC

Valeriana wallichii DC, a high-altitude medicinal plant, is highly sensitive to drought stress, which adversely impacts its physiological functions and root biomass. This study aimed to evaluate salicylic acids role in mitigating drought stress by assessing physiological and biochemical responses in V. wallichii. Plants were treated with foliar applications of SA at concentrations of 0.25, 0.50, 0.75, and 1.0 mM during vegetative and flowering stages. Physiological parameters such as photosynthetic rate, stomatal conductance, water use efficiency (WUE), intrinsic WUE (iWUE), carboxylation efficiency, and biochemical traits including chlorophyll and carotenoid content were measured, alongside fresh and dry root biomass.Drought stress significantly reduced photosynthetic performance (Pn) (3.95 mol CO2m{square}2s{square}1 at 25% FC), stomatal conductance, relative water content, and root yield. SA application notably improved these traits. At 25% FC, 1.0 mM SA enhanced WUE (28.78), iWUE (642.37 mol/mol), and fresh root weight (8.41 g). Under moderate drought (50% FC), 0.50 mM SA improved net photosynthesis (12.5 mol CO2 m{square}2s{square}1), dry root weight (2.31 g), and chlorophyll content. SA treatments also stabilized membrane integrity and maintained higher chlorophyll fluorescence efficiency (Fv/Fm).These findings demonstrate that foliar application of SA enhances drought tolerance in V. wallichii by improving photosynthetic efficiency, water relations, and root biomass. The study supports the strategic use of SA to improve the resilience and productivity of medicinal plants under drought stress conditions. Highlights of the studyO_LIDrought lowers growth and yield by reducing photosynthesis and water use. C_LIO_LISalicylic acid reduces drought effects and improves plant performance. C_LIO_LIAt severe drought, 1- 0.50 mM SA raised WUE, conductance, and root yield. C_LIO_LIUnder mild drought, 0.75- 0.50 mM SA improved gas exchange and yield. C_LIO_LISA doses 0.25-1 mM differ in effectiveness across drought stress stages. C_LI

plant biology↗

bioRxiv2020

pH dependent inhibition from ammonium ions in the Pseudomonas mevalonii HMG-CoA Reductase crystallization environment

HMG-CoA reductase (Pseudomonas mevalonii) utilizes mevalonate, coenzyme A (CoA) and the cofactor NAD in a complex mechanism involving two hydride transfers with cofactor exchange, accompanied by large conformational changes by a 50 residue subdomain, to generate HMG-CoA. Details about this mechanism such as the conformational changes that allow intermediate formation, cofactor exchange and product release remain unknown. The formation of the proposed intermediates has also not been observed in structural studies with natural substrates. Having been shown to be an essential enzyme for the survival of gram-positive antibiotic resistant pathogenic bacteria, studying its mechanism in detail will be beneficial in developing novel antibacterials. The enzyme has been shown to be catalytically active inside the crystal with dithio-HMG-CoA and NADH but curiously is found to be inactive in the reverse direction in the structure bound to mevalonate, CoA and NAD. To understand the factors limiting activity in the HMGR crystal with mevalonate, CoA and NAD, we studied the effect of crystallization components and pH on enzymatic activity. We observed a strong inhibition in the crystallization buffer and an increase in activity with increasing pH. We attribute this inhibitive effect to the presence of ammonium ions present in the crystal since inhibition is also observed with several other ammonium salt buffers. Additionally, the lack of inhibition was observed in the absence of ammonium. The effect of each ligand (mevalonate, CoA and NAD) on the rate of the enzymatic reaction in the crystallization environment was further investigated by measuring their Km in the crystallization buffer. The Km measurements indicate that the hydride transfer step between NAD and mevalonate is inhibited in the crystallization environment. To test this further, we solved a crystal structure of pmHMGR bound to the post-hydride transfer intermediate (mevaldehyde) and cofactor Coenzyme A. The resulting turnover with the formation of a thiohemiacetal indicated that the crystallization environment inhibited the oxidative acylation of mevalonate and the reaction intermediate mevaldyl-CoA.

biochemistry↗

bioRxiv2019

Induction of pancreatic tumor-selective ferroptosis through modulation of cystine import

Pancreatic ductal adenocarcinoma (PDA) is the third-leading cause of cancer mortality in the US and is highly resistant to classical, targeted, and immune therapies. We show that human PDA cells are dependent on the provision of exogenous cystine to avert a catastrophic accumulation of lipid reactive oxygen species (ROS) that, left unchecked, leads to ferroptotic cell death, both in vitro and in vivo. Using a dual-recombinase genetically engineered model, we found that acute deletion of Slc7a11 led to tumor-selective ferroptosis, tumor stabilizations/regressions, and extended overall survival. The mechanism of ferroptosis induction in PDA cells required the concerted depletion of both glutathione and coenzyme A, highlighting a novel branch of ferroptosis-relevant metabolism. Finally, we found that cystine depletion in vivo using the pre-IND agent cyst(e)inase phenocopied Slc7a11 deletion, inducing tumor-selective ferroptosis and disease stabilizations/regressions in the well-validated KPC model of PDA.\n\nOne Sentence SummaryGenetic and pharmacological targeting of cystine import induces pancreatic cancer-selective ferroptosis in vivo.

cancer biology↗

bioRxiv2019

Integration of high-content fluorescence imaging into the metabolic flux assay reveals insights into mitochondrial properties and functions

Metabolic flux technology with the Seahorse bioanalyzer has emerged as a standard technique in cellular metabolism studies, allowing for simultaneous kinetic measurements of respiration and glycolysis. Methods to extend the utility and versatility of the metabolic flux assay would undoubtedly have immediate and wide-reaching impacts. Herein, we describe a platform that couples the metabolic flux assay with high-content fluorescence imaging to simultaneously enhance normalization of respiration data with cell number; analyze cell cycle progression; quantify mitochondrial content, fragmentation state, membrane potential, and mitochondrial reactive oxygen species. Integration of fluorescent dyes directly into the metabolic flux assay generates a more complete data set of mitochondrial features in a single assay. Moreover, application of this integrated strategy revealed insights into mitochondrial function following PGC1a and PRC1 inhibition in pancreatic cancer and demonstrated how the Rho-GTPases impact mitochondrial dynamics in breast cancer.

molecular biology↗