Biology subjects

Raju, K.

Publications and source records attributed to Raju, K..

3 recordsLinked to original sources

bioRxiv2021

Postsynaptic synucleins mediate vesicular exocytosis of endocannabinoids

Two seemingly unrelated questions have long motivated studies in neuroscience: How are endocannabinoids, among the most powerful modulators of synaptic transmission, released from neurons? What are the physiological functions of synucleins, key contributors to Parkinsons Disease? Here, we report an unexpected convergence of these two questions: Endocannabinoids are released via vesicular exocytosis from postsynaptic neurons by a synuclein-dependent mechanism. Specifically, we find that deletion of all synucleins selectively blocks all endocannabinoid-dependent synaptic plasticity; this block is reversed by postsynaptic expression of wildtype but not of mutant -synuclein. Loading postsynaptic neurons with endocannabinoids via patch-pipette dialysis suppressed presynaptic neurotransmitter release in wildtype but not in synuclein-deficient neurons, suggesting that the synuclein deletion blocks endocannabinoid release. Direct optical monitoring of endocannabinoid release confirmed the requirement of synucleins. Given the role of synucleins in vesicular exocytosis, the requirement for synucleins in endocannabinoid release indicates that endocannabinoids are secreted via exocytosis. Consistent with this hypothesis, postsynaptic expression of tetanus-toxin light chain, which cleaves synaptobrevin SNAREs, also blocked endocannabinoid-dependent plasticity and release. The unexpected finding that endocannabinoids are released via synuclein-dependent exocytosis assigns a function to synucleins and resolves a longstanding puzzle of how neurons release endocannabinoids to induce synaptic plasticity.

neuroscience↗

bioRxiv2020

Influence of spatial arrangement, biofertilizers and bioirrigation on the performance of legume-millet intercropping system in rainfed areas of southern India

Biofertilization via the inoculation with arbuscular mycorrhizal fungi (AMF), combined with rhizobia and plant growth promoting rhizobacteria (PGPR), are beginning to become established as an effective and sustainable measure to improve yields. Biofertilization might have a particular potential to boost the yield of intercropping systems in rainfed areas because AMF can form a common mycorrhizal network (CMN) that can transfer nutrients and water between two plants and balance as such belowground competition. In this study, we tested if biofertilizers can enhance the yield of intercropping systems using a pigeon pea (PP) - finger millet (FM) intercropping system grown for two consecutive growing seasons (2016/17 and 2017/18) at two contrasting sites in Bengaluru and Kolli Hills, India. To validate the process of bioirrigation (transfer of water between rhizosphere of two plants), we tested, for the first time, if the spatial arrangement of intercropped plants using either a row-wise or a mosaic design affected yield and water relations with and without biofertilizers. Our results demonstrate that intercropping can improve the straw and grain yield in PP-FM intercropping compared to the respective monocultures but that intercropping effects vary depending on the site characteristic such as climate and soil type. Spatial arrangement of component plants affected the total, straw and grain biomass in intercropping treatments, but this effect also varied across sites. Most importantly, the results from the 2017-18 growing season clearly demonstrated a positive effect of biofertilizer on biomass yield, and this effect was irrespective of site, spatial arrangement, mixed or monoculture. Despite a yield increase in intercropping, we did not see a positive effect of biofertilization on water relations of FM possibly due to interspecific competition for soil moisture where PP dominated. In summary, our study shows the potential of biofertilizers to increase the yield of intercropping systems in rainfed dryland agriculture.

ecology↗

bioRxiv2020

Astrocytic Neurexin-1 Orchestrates Functional Synapse Assembly

At tripartite synapses, astrocytes enmesh synaptic contacts, but how astrocytes contribute to the formation, maturation and plasticity of synapses remains elusive. Here we show that both astrocytes and neurons abundantly express neurexin-1, a presynaptic adhesion molecule that controls synaptic properties. Using super-resolution imaging, we demonstrate that presynaptic neuronal and astrocytic neurexin-1 form discrete nanoclusters at excitatory synapses. We find that distinct patterns of heparan sulfate modification and alternative splicing confer onto astrocytic and neuronal neurexin-1 different ligand specificities, thereby enabling compartment-specific signaling by neurexin-1. At hippocampal Schaffer-collateral synapses, deletion of neurexin-1 from either astrocytes or neurons did not alter synapse numbers, but differentially impaired synapse function. Neuronal neurexin-1 was essential for NMDA-receptor-mediated synaptic responses, whereas astrocytic neurexin-1 was required for maturation of silent synapses, AMPA-receptor recruitment, and long-term potentiation. Thus, astrocytes and neurons surprisingly use the same synaptic adhesion molecule to control distinct synapse properties.

neuroscience↗