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Biology subjects

Shameer, S.

Publications and source records attributed to Shameer, S..

5 recordsLinked to original sources

Genome-scale prediction of context-specific synthetic lethality beyond protein interaction networks

Identifying synthetic lethal (SL) interactions offers a principled framework for discovering disease-specific therapeutic targets. However, current machine learning approaches heavily rely on curated protein-protein interaction networks. Because these networks cover only [~]7,500 proteins, they severely restrict the search space of human gene pairs and introduce systematic biases toward well-characterized genes. To circumvent these limitations, we developed SLxGO, a network-independent machine learning framework that predicts SL interactions directly from semantic representations of Gene Ontology annotations encoded via BioBERT-derived embeddings. Benchmarked across multiple cross-validation schemes against eight state-of-the-art methods, SLxGO consistently achieved superior predictive ranking performance, maintaining robustness under cold-start conditions for previously unseen genes. Integrating cell line-specific transcriptional profiles extended this framework to context-dependent SL prediction across six distinct cell lines. Notably, we experimentally confirmed a context-specific EFNA1-SLC29A1 SL interaction in HeLa cells, alongside synergistic pharmacological validation of an ACVR1-SLC29A1 vulnerability. All predictions are hosted on SLiGO, an open-access database encompassing 30 million human gene pairs, establishing a comprehensive, genome-scale resource for context-specific vulnerability mapping across the human interactome.

systems biology↗

Leaf specific overexpression of a mitochondrially-targeted glutamine synthetase in tomato increased assimilate export resulting in earlier fruiting and elevated yield

To identify potential strategies for increasing the efficiency of tomato leaf metabolism, with a focus on the links between nitrogen/carbon metabolism, we explored a diel Flux Balance Analysis (FBA) model of a source leaf in which the metabolic output was varied up to the theoretically-achievable maximum. We noticed a potentially interesting switch in the use of glutamine synthetase (GS) isoforms -from the chloroplast isoform to the mitochondrial one- for nitrogen assimilation. To further explore this prediction, we characterized transgenic tomato plants over-expressing two tomato GS genes, GS1 and GS2, targeted to mitochondria. Both sets of transgenic plants were characterized as displaying faster growth rate, early flowering and increased fruit yield. In leaves, metabolomic profiling and enzyme activity analysis pointed that GS activity in mitochondrial plays a role in increasing the intracellular synthesis and subsequent export of sugar. Consistent with these changes, higher sucrose concentration in leaf exudates and reduced activities of enzymes involved in leaf starch synthesis were observed. Moreover, mitochondrial GS activity affected chloroplast redox status in a manner that modulated photorespiration and nitrogen metabolism. The combined data reveal the influence of mitochondrial GS activity on both foliar carbon/nitrogen balance and regulation of source-sink metabolism in tomato plants.

plant biology↗

CAM emerges in a leaf metabolic model under water-saving constraints in different environments

Crassulacean Acid Metabolism (CAM) evolved in arid environments as a water-saving alternative to C3 photosynthesis. There is great interest in engineering more drought-resistant crop species by introducing CAM into C3 plants. However, one of the open questions is whether full CAM or alternative water-saving flux modes would be more productive in the environments typically experienced by C3 crops. To study the effect of temperature and relative humidity on plant metabolism we coupled a time-resolved diel model of leaf metabolism to an environment-dependent gas-exchange model. This model allowed us to study the emergence of CAM or CAM-like behaviour as a result of a trade-off between leaf productivity and water-saving. We show that vacuolar storage capacity in the leaf is a major determinant of the extent of CAM and shapes the occurrence of phase II and IV of the CAM cycle. Moreover, the model allows us to study alternative flux routes and we identify mitochondrial isocitrate dehydrogenase (ICDH) and an isocitrate-citrate-proline-2OG cycle as a potential contributor to initial carbon fixation at night. Simulations across a wide range of environmental parameters show that the water-saving potential of CAM strongly depends on the environment and that the additional water-saving effect of carbon fixation by ICDH can reach up to 4% for the conditions tested.

plant biology↗

Predicting metabolism during growth by osmotic cell expansion

Cell expansion is a significant contributor to organ growth and is driven by the accumulation of osmolytes to increase cell turgor pressure. Metabolic modelling has the potential to provide insights into the processes that underpin osmolyte synthesis and transport, but the main computational approach for predicting metabolic network fluxes, flux balance analysis (FBA), typically uses biomass composition as the main output constraint and ignores potential changes in cell volume. Here we present GrOE-FBA (Growth by Osmotic Expansion-Flux Balance Analysis), a framework that accounts for both the metabolic and ionic contributions to the osmotica that drive cell expansion, as well as the synthesis of protein, cell wall and cell membrane components required for cell enlargement. Using GrOE-FBA, the metabolic fluxes in dividing and expanding cell were analyzed, and the energetic costs for metabolite biosynthesis and accumulation in the two scenarios were found to be surprisingly similar. The expansion phase of tomato fruit growth was also modelled using a multi-phase single optimization GrOE-FBA model and this approach gave accurate predictions of the major metabolite levels throughout fruit development as well as revealing a role for transitory starch accumulation in ensuring optimal fruit development.

plant biology↗

Tyrosinase mediated humic substances synthesis by Bacillus aryabhattaiTFG5

The present investigation aims at understanding the mechanism of Humic Substances (HS) formation and enhancement through tyrosinase produced by Bacillus aryabhattai TFG5. A bacterium isolated from termite mound produced tyrosinase (1.34 U.ml-1) and laccase (2.1 U.ml-1) at 48 and 60 h of fermentation respectively. The protein from B. aryabhattai TFG5 was designated as TyrB and it had a predicted molecular weight of 35.23 kDa. Swiss modelling of protein revealed a bi copper protein with its conserved residues required for activity. Interestingly, TyrB efficiently transformed and polymerized standard phenols besides transforming free phenols of Coir pith Wash Water (CWW). In addition, spectroscopic evidences suggest that TyrB enhanced the HS production from coir pith biomass. Furthermore, degradative products and changes in biomass structure by TyrB analysed through FT-IR suggests that TyrB might follow the polyphenol theory of HS synthesis.

microbiology↗