Biology subjects

Silber, A.

Publications and source records attributed to Silber, A..

3 recordsLinked to original sources

bioRxiv2025

Nuclear proteome analysis reveals spatial and temporal compartmentalization of metabolic enzymes during Trypanosoma cruzi cell cycle

Trypanosoma cruzi, the etiological agent of Chagas Disease (CD), represents a significant public health concern and serves as a valuable model for investigating the cell cycle in early-diverging eukaryotes. Its unique cellular features--including the absence of chromosome condensation and the coordination of nuclear division with specialized organelles--provide insights into non-canonical regulatory mechanisms, and underscore the pivotal role of the nucleus in maintaining genomic integrity and regulating fundamental processes such as DNA replication and gene expression. To investigate nuclear dynamics throughout the cell cycle, we synchronized T. cruzi epimastigotes at G1/S, S, and G2/M using hydroxyurea (HU), and isolated nuclear proteins were quantitative evaluated by LC-MS/MS. We identified 2,937 nuclear-enriched proteins, revealing distinct, phase-specific expression patterns. The G1/S phase was marked by increased levels of metabolic enzymes including those related to energy and nucleotide/nucleoside metabolisms. The S phase showed elevated abundance of canonical and variant histones, consistent with chromatin remodeling and DNA replication. The G2/M phase was enriched in proteins involved in protein synthesis and microtubule dynamics, essential for mitosis. Notably, [~]6% of the nuclear proteome consisted of metabolic enzymes, a finding further supported by other public proteomics datasets and in vitro nuclear activity assays. These results suggest that metabolic enzymes and/or their metabolites may modulate nuclear processes in T. cruzi, potentially influencing the epigenome and gene expression regulation, as proposed in other eukaryotic models. Altogether, our findings reveal dynamic remodeling of the nuclear proteome during the T. cruzi cell cycle and point to a previously underappreciated role for metabolic enzymes likely regulating nuclear functions in a cell cycle-dependent manner.

microbiology↗

bioRxiv2021

Nitrogen uptake and macronutrients distribution in mango trees (cv. Keitt) under three N fertigation treatments

We assessed the effects of N concentration in the irrigation water on nutrient uptake and distribution in leaves and fruit of mango cv. Keitt grown in a lysimeter for four years. We applied three treatments: N1 - no N fertilization (less than 2 mg/L in the tap water); N2 - 10 mg/L N; N3 - 20 mg/L N. Deficient N conditions (N1) generated low vegetative yield, high fruit:leaf ratio, high photosynthetic activity, high leaf P and K concentrations, and high sugar content along with low acidity in the fruit. Excess N concentration (N3) induced vegetative growth, and reduced fruit yield and gas-exchange characteristics. The calculated annual nitrogen uptake heavily depended on the nitrogen supply (N1-26 g/tree; N2-196 g/tree; N3- 185 g/tree). Fruits were the major N sink being 0.82, 0.26 and 0.05 from the total annual N supplied. The N quantities accumulated in N1 fruits during the reproductive season (May-August), were above the N quantities supplied via fertigation, suggesting that N reserve in the vegetative tissues supplied the fruits high N demand. The finding shows the importance of adequate nitrogen supply to mango trees and the dangers of excessive fertilization.

physiology↗

bioRxiv2020

Fly stage trypanosomes recycle glucose catabolites and TCA cycle intermediates to stimulate growth in near physiological conditions

Trypanosoma brucei, a protist responsible for human African trypanosomiasis (sleeping sickness), is transmitted by the tsetse fly, where the procyclic forms of the parasite develop in the proline-rich (1-2 mM) and glucose-depleted digestive tract. Proline is essential for the midgut colonization of the parasite in the insect vector, however other carbon sources could be available and used to feed its central metabolism. Here we show that procyclic trypanosomes can consume and metabolize metabolic intermediates, including those excreted from glucose catabolism (succinate, alanine and pyruvate), with the exception of acetate, which is the ultimate end-product excreted by the parasite. Among the tested metabolites, tricarboxylic acid (TCA) cycle intermediates (succinate, malate and -ketoglutarate) stimulated growth of the parasite in the presence of 2 mM proline. The pathways used for their metabolism were mapped by proton-NMR metabolic profiling and phenotypic analyses of a dozen RNAi and/or null mutants affecting central carbon metabolism. We showed that (i) malate is converted to succinate by both the reducing and oxidative branches of the TCA cycle, which demonstrates that procyclic trypanosomes can use the full TCA cycle, (ii) the enormous rate of -ketoglutarate consumption (15-times higher than glucose) is possible thanks to the balanced production and consumption of NADH at the substrate level and (iii) -ketoglutarate is toxic for trypanosomes if not appropriately metabolized as observed for an -ketoglutarate dehydrogenase null mutant. In addition, epimastigotes produced from procyclics upon overexpression of RBP6, showed a growth defect in the presence of 2 mM proline, which is rescued by -ketoglutarate, suggesting that physiological amounts of proline are not sufficient per se for the development of trypanosomes in the fly. In conclusion, these data show that trypanosomes can metabolize multiple metabolites, in addition to proline, which allows them to confront challenging environments in the fly. Author SummaryIn the midgut of its insect vector, trypanosomes rely on proline to feed their energy metabolism. However, the availability of other potential carbon sources that can be used by the parasite is currently unknown. Here we show that tricarboxylic acid (TCA) cycle intermediates, i.e. succinate, malate and -ketoglutarate, stimulate growth of procyclic trypanosomes incubated in medium containing 2 mM proline, which is in the range of the amounts measured in the midgut of the fly. Some of these additional carbon sources are needed for the development of epimastigotes, which differentiate from procyclics in the midgut of the fly, since their growth defect observed in the presence of 2 mM proline is rescued by addition of -ketoglutarate. In addition, we have implemented new approaches to study a poorly explored branch of the TCA cycle converting malate to -ketoglutarate, which was previously described as non-functional in the parasite, regardless of the glucose levels available. The discovery of this branch reveals that a full TCA cycle can operate in procyclic trypanosomes. Our data broaden the metabolic potential of trypanosomes and pave the way for a better understanding of the parasites metabolism in various organ systems of the tsetse fly, where it evolves.

microbiology↗