Biology subjects

Sundram, S.

Publications and source records attributed to Sundram, S..

5 recordsLinked to original sources

bioRxiv2026

Evaluating cacao pod resistance to black pod disease caused by three Phytophthora species

Black pod disease is a major threat to global cacao (Theobroma cacao L.) production. It is caused by multiple Phytophthora species with geographic ranges from regionally restricted to pantropical, and developing resistant cultivars requires screening against the diversity of these pathogens. This study evaluated the response of 25 cacao clones to 13 isolates of P. palmivora (eight), P. megakarya (two), and P. theobromicola (three) by nonwounding inoculation of detached pods. Lesion size and lesion expansion status were evaluated 4 days after inoculation. The linear mixed model included 178 combinations among 17 clones and 12 isolates, each represented by at least two biological replicate pods. Lesion size differed among clones (F(16, 449.2) = 25.16) and among isolates (F(11, 416.0) = 32.90), and the clone by isolate interaction was significant (F(150, 465.4) = 1.72; all P < 0.001). PENTAGONA-17 had the smallest estimated marginal lesion size (9.3 mm) and fitted values of 3.8 to 16.9 mm across 11 isolates representing all three species. ARF-31, ICS-47, POUND-7, and PMCT-73 had the next four smallest estimates, whereas NA-246 had the largest (36.7 mm). Isolate estimates varied more than fourfold, from 9.6 to 42.0 mm. Despite a marginal estimate of 12.9 mm, POUND-7 had a fitted estimate of 49.2 mm with P. megakarya GH34. The probability of lesion expansion also differed among clones and isolates (both P < 0.001). Together, these findings identify candidates for further resistance evaluation and show that multi-isolate screening provides a stronger basis for selecting materials for black pod resistance breeding.

plant biology↗

bioRxiv2025

Generation of two Betacellulin CRISPR-Cas9 knockout hiPSC lines to study affected EGF system paradigm in Schizophrenia

Several members of the epidermal growth factor (EGF) family have been implicated in the biology of schizophrenia (Ketharanathan et al., 2024). The EGF-related ligand, Betacellulin (BTC), plays an important role in the proliferation and differentiation of neural stem cells and our group found markedly reduced BTC levels in patients with schizophrenia. Nevertheless, the interplay of affected BTC and its participation in neural specification and neurodevelopment remains elusive. We generated Knockout (KO) - BTC clones from an existing hiPSC line through CRISPR/Cas9-mediated modification. Furthermore, we validated BTC-KO through genotyping/sequencing, FACS and Western Blot. Finally, we demonstrated trilineage differentiation potential in vitro.

neuroscience↗

bioRxiv2025

Psychedelics Align Brain Activity with Context

Psychedelics can profoundly alter consciousness by reorganising brain connectivity; however, their effects are context-sensitive. To understand how this reorganisation depends on context, we collected and comprehensively analysed the largest psychedelic neuroimaging dataset to date. Sixty-two adults were scanned with functional MRI and EEG during rest and naturalistic stimuli (meditation, music, and movie), before and after ingesting 19 mg of psilocybin (functional MRI {approx}80 min post-dose; EEG {approx}150 min post-dose). Half the participants ranked the experience among the most meaningful of their lives. Under psilocybin, functional MRI and EEG signals recorded during eyes-closed conditions became similar to those recorded during an eyes-open condition. Global functional connectivity increased in associative regions and decreased in sensory areas. Using machine learning to represent neural activity as low-dimensional trajectories, we found that psilocybin reorganised these into structured, context-sensitive patterns of brain activity that reflected both experimental condition and the quality of subjective experience, revealing an organisation that was missed by time-averaged connectivity measures. Under psilocybin, brain networks that ordinarily segregate internal and external processing coherently integrated and aligned neural dynamics with context. This context-alignment manifested as distinct and cohesive neural trajectories in participants reporting positively felt self- and boundary-dissolving effects, corresponding to the felt experience of being part of the environment, which we refer to as embeddedness--the subjective experience of being continuous with, rather than separate from, the surrounding environment. The strength of this context-alignment was associated with next-day mindset change, bridging the neural, experiential, and therapeutic dimensions of the psychedelic state. These findings show that the organisation of brain activity covaries with the experiential coherence of the psychedelic state, and provide a systems-level framework for how context-sensitive brain dynamics link neurobiology to subjective experience and behavioural change.

neuroscience↗

bioRxiv2022

Mouse behaviour on the trial-unique non-matching-to-location (TUNL) touchscreen task reflects a mixture of distinct working memory codes and response biases

The trial-unique non-matching to location (TUNL) touchscreen task shows promise as a translational assay of working memory deficits in disorders including autism, ADHD, and schizophrenia. Although it is commonly assumed that the TUNL task predominantly measures spatial working memory in rodents, this proposition has not previously been tested. In this project, we used computational modelling of behaviour from mice performing the TUNL task (total N = 163 mice across three datasets; 158,843 total trials). Contrary to common assumptions, behaviour on the TUNL task did not exclusively reflect spatial working memory. Instead, choice behaviour was explained as a mixture of both retrospective (spatial) working memory and prospective working memory for an intended behavioural response, as well as animal-specific response biases. We suggest that these findings can be understood within a resource-rational cognitive framework, and propose several task-design principles that we predict will maximise spatial working memory and minimise alternative behavioural strategies.

animal behavior and cognition↗

bioRxiv2019

Aberrant connectivity in auditory precision encoding in schizophrenia spectrum disorder and across the continuum of psychotic-like experiences

BackgroundThe ability to generate a precise internal model of statistical regularities is impaired in schizophrenia. Predictive coding accounts of schizophrenia suggest that psychotic symptoms may be explained by a failure to build precise beliefs or a model of the world. The precision of this model may vary with context. For example, in a noisy environment the model will be more imprecise compared to a model built in an environment with lower noise. However compelling, this idea has not yet been empirically studied in schizophrenia. Methods: In this study, 62 participants engaged in a stochastic mismatch negativity paradigm with high and low precision. We included inpatients with a schizophrenia spectrum disorder (N=20), inpatients with a psychiatric disorder but without psychosis (N=20), and healthy controls (N=22), with comparable sex ratio and age distribution. Bayesian mapping and dynamic causal modelling were employed to investigate the underlying microcircuitry of precision encoding of auditory stimuli. Results: We found strong evidence (exceedance p > 0.99) for differences in the underlying connectivity associated with precision encoding between the three groups as well as on the continuum of psychotic-like experiences assessed across all participants. Critically, we show changes in interhemispheric connectivity between the two inpatient groups, with some connections further aligning on the continuum of psychotic-like experiences. Conclusions: While our results suggest continuity in backward connectivity alterations with psychotic-like experiences regardless of diagnosis, they also point to specificity for the schizophrenia spectrum disorder group in interhemispheric connectivity alterations.

neuroscience↗