Biology subjects

M, M.

Publications and source records attributed to M, M..

8 recordsLinked to original sources

bioRxiv2025

Reinforcement of speciation by behavioural and reproductive barriers in the Drosophila bipectinata species complex

Speciation mainly depends on different mechanisms involved in reproductive isolation; Understanding such barriers that consistently develop to avoid the fitness cost through reinforcement until the speciation continuum completes helps clarify the role of pre-mating and post-mating isolating mechanisms. The Drosophila bipectinata species complex, comprising four closely related taxa, provides a natural system for studying the interplay of behavioural, sensory, and genetic mechanisms underlying reproductive isolation. In this study, a comprehensive characterization was undertaken on twelve different types of sterile F1 hybrid males among the crosses between four species of Drosophila bipectinata species complex which are experiencing reproductive isolation. Comparing the mating latency and copulation duration among the pure species and hybrids, showed a significant increase in the mating latency of hybrids but the duration of copulation among certain hybrids of Drosophila bipectinata, Drosophila parabipectinata and Drosophila malerkotliana showed no significant reduction in the copulation time and emphasized the strong influence of X chromosome inheritance of hybrid genome. Experimental ablation of antennae demonstrated that male olfactory input is indispensable for heterospecific mating success, consistent with the role of pheromone detection in conspecific recognition, while tarsi ablation revealed striking sex-specific asymmetry: male tarsi removal increased heterospecific success, whereas female tarsi removal abolished mating entirely, highlighting the role of gustatory receptors in female mate choice. Testis dissections further confirmed that post-meiotic defects in hybrids, including failure of spermatid elongation and individualization, these findings demonstrates that reproductive isolation in the D. bipectinata species complex arises from the collective action of multiple barriers, prezygotic isolation mediated by pheromonal and gustatory divergence, and postzygotic sterility driven by spermatogenic failure. Our study underscores how behavioural and physiological divergence interact to reinforce reproductive barriers, providing a comprehensive framework for understanding speciation in Drosophila.

genetics↗

bioRxiv2025

Cis-regulatory divergence and misexpression of spermatogenesis genes underlie hybrid male sterility in the Drosophila bipectinata species complex

Hybrid male sterility (HMS) is one of the most common and earliest forms of postzygotic reproductive isolation in Drosophila, often arising from defects in spermatogenesis linked to regulatory divergence of rapidly evolving male-biased genes. The Drosophila bipectinata species complex (D. bipectinata, D. malerkotliana, D. parabipectinata, and D. pseudoananassae) provides a valuable system to study the speciation paradigm, since, all the twelve F hybrid males are sterile, the precise stage of spermatogenic failure differs among crosses. Here, we integrate cytological, transcriptional, and regulatory sequence analyses to examine the basis of sterility in this sub-complex. Cytological assays revealed that hybrid testes exhibit developmental arrest at different spermatogenesis stages, covering from reduced primary spermatocytes to absence of individualized sperm. Quantitative RT-PCR of seven spermatogenesis genes--aly, bam, sa, dj, topi, can, and Mst98Ca--showed significant downregulation among hybrid males relative to parental species, linking transcriptional misregulation with observed phenotypic defects in spermatogenesis. To test whether regulatory divergence underlies this misexpression, we analyzed [~]1-2 kb promoter regions of five genes (aly, bam, sa, dj, and topi). Motif scans using FIMO identified several lineage-specific turnover of transcription factor binding sites, also PWM-delta analysis revealed substantial interspecific differences in predicted binding strength for many key testis transcription factors. These results demonstrate that HMS in the D. bipectinata complex is consistently associated with spermatogenic arrest and misregulation of genes essential for germline proliferation, meiotic progression, and spermiogenesis. The concordance between expression changes and promoter divergence supports a role for cis-regulatory evolution in hybrid dysfunction, while also leaving open the contribution of trans-acting factors. This study situates the D. bipectinata complex within the broader framework of Drosophila hybrid sterility, extending and highlighting the evolutionary sensitivity of spermatogenesis and regulatory divergence in speciation.

evolutionary biology↗

bioRxiv2024

Multi-source photographic evidence to assess corridor use, crop-raiding behaviour, and body injuries in Asian elephants

This study investigated the use of multi-sourced photographs, such as those from social media, camera traps, and field surveys, for individual identification of male Asian elephants to study their corridor use, crop-raiding behaviour, occurrence of musth, ranging and external body injuries in the Thirunelli-Kudrakote elephant corridor in Indias Western Ghats. A total of 330 images and videos were analysed over 11 years (January 2014 to March 2024), leading to the identification of 27 male elephants from the corridor. Eleven individuals were observed across multiple years, demonstrating their fidelity to the area. Ten elephants were observed engaging in crop-raiding, with four consistently raiding crops within the corridor. The study also assessed the home range of 6 individuals in the corridor and adjacent landscapes based on individual identification. Overall, the study shows that identifying individual elephants across different locations and times provides valuable data and is a practical, cost-effective method for investigating a wide range of questions concerning the ecology and behaviour of Asian elephants. The findings underscore the potential of citizen science initiatives to enhance elephant research across elephant-range countries.

ecology↗

bioRxiv2023

Description of Protosticta sexcoloratus sp. nov. (Odonata, Platystictidae) from the Western Ghats, India

Protosticta Selys, 1885 is a speciose genus of damselflies distributed in the tropical and subtropical forests of Asia. During an ongoing study to document the odonate diversity of the Western Ghats, we came across a colony of Protosticta species in Wayanad, Kerala, that appeared different from all other species hitherto described. We describe this population as a new species after detailed morphological comparison with closely similar species occurring in the region.

zoology↗

bioRxiv2022

Qualitative determination of bioactive metabolites of chyawanprash by using Gas Chromatography-Mass Spectroscopy

Chyawanprash is a rich source of all the major bioactive metabolites because of its authentic and natural composition and widely used due to its medicinal properties. In the present study, the precise flow of analytical methods was employed for the identification and characterization of unknown secondary metabolites in Chyawanprash. The phytochemical components of the whole formulation were extracted using n-hexane, ethyl acetate, and methanol by maceration which shows the presence of all the major secondary metabolite components through preliminary qualitative phytochemical screening. The GC-MS analysis of different extracts of Chyawanprash was investigated using Clarus 680 GC (Perkin-Elmer (U. S. A) 30 m X 0.25 mm ID X 250 m DF) which revealed the presence of total 15 unknown secondary metabolites. Finally, the results showed that the study forms the basis for the phytochemical characterization of Chyawanprash extracts, the isolation of responsible bio-active metabolites and their biological activity is necessary for future studies.

pharmacology and toxicology↗

bioRxiv2021

Mutated in Colorectal Cancer (MCC): a centrosomal protein that relocalizes to the ncMTOC during intestinal cell differentiation

Mutated in Colorectal Cancer (MCC) encodes a coiled-coil protein implicated, as its name suggests, in the pathogenesis of hereditary human colon cancer. To date, however, the contributions of MCC to intestinal homeostasis remain unclear. Here, we examine the subcellular localization of MCC, both at the mRNA and protein levels, in the adult intestinal epithelium. Our findings reveal that Mcc transcripts are restricted to proliferating crypt cells, including Lgr5+ stem cells, and that Mcc protein is distinctly associated with the centrosome in these cells. Upon intestinal cellular differentiation, Mcc is redeployed to the non-centrosomal microtubule organizing center (ncMTOC) at the apical domain of villus cells. Using intestinal organoids, we show that the shuttling of the Mcc protein depends on phosphorylation by Casein Kinases 1{delta}/{varepsilon}, which are critical modulators of WNT signaling. Together, our findings support a putative role for MCC in establishing and maintaining the cellular architecture of the intestinal epithelium as a component of both the centrosome and ncMTOC.

cell biology↗

bioRxiv2019

Listing candidate diagnostic markers and exploring the molecular basis of human spermatogenesis and a type of male infertility (Non-Obstructive Azoospermia), with transcriptomics via the next generation sequencing methods

Studying the molecular basis of Non-Obstructive Azoospermia (NOA), a type of male infertility with failed spermatogenesis at various stages, can also help in exploring molecular basis of human spermatogenesis and possibly pave way to identify new targets for male contraceptive development. Hence, we initiated a functional genomics study by applying RNA-seq. Testicular biopsies collected from donors with Non-Obstructive Azoospermia (NOA), Obstructive Azoospermia (OA), Congenital Bilateral Absence of the Vas Deferens (CBAVD), and Varicocele (VA) conditions. Strong association of 100+ genes with human spermatogenesis and NOA has been detected via NGS-based transcriptomic analysis. In addition, 20 RNA molecules have been short-listed for potential diagnostic applications (non-obstructive azoospermia vs. obstructive azoospermia, varicocele or normal). A hierarchical list of several genes and alternatively spliced mRNAs, transcribed differentially in NOA, is reported - based on a strength of association. Such association with NOA, spermatogenesis or both is a new finding for many genes as revealed by a comparison with a newly prepared comprehensive list of genes having such association with human spermatogenesis/NOA. Many top-ranking genes involved in viral gene expression were up-regulated in testes from NOA-patients, while those associated with an antiviral mechanism were down-regulated. A tangential finding: while most well-established control mRNAs did not qualify, two new ones worked best in RT-qPCR experiments. Needle-aspiration of testicular biopsies, followed by the use of short-listed promising candidate biomarkers (i.e., 16 mRNA & 4 chimeric transcripts) and control mRNAs in RT-qPCR-based diagnostic assays, may help to avoid open surgeries in future.

developmental biology↗

bioRxiv2018

Neuropeptides required for Drosophila development under nutritional stress are regulated by the ER-Ca2+ sensor STIM

SignificanceElevation of cytosolic Ca2+ is required for the release of neuropeptides from specialised secretory neurons called neuroendocrine cells. Release of Ca2+ stored in the ER, which further triggers Ca2+ entry from the extracellular milieu is called Store-operated Ca2+ entry (SOCE). STIM, an ER protein, is a key regulator of SOCE and its contribution to neuroendocrine cell functioning is not well studied. Using Drosophila larval development under nutrient restriction as a paradigm, we identified two SOCE regulated neuropeptides, Corazonin and short Neuropeptide F. Reducing STIM alters the level of these neuropeptides in the fed as well as nutrient restricted condition. This study suggests that STIM-triggered SOCE may regulate the release of neuropeptides whose activity ultimately regulates adaptation to nutritional stress.\n\nAbstractCytosolic Ca2+ levels are tightly regulated by the sequestration of Ca2+ within the endoplasmic reticulum (ER). Loss of ER Ca2+ is sensed by STromal Interacting Molecule (STIM), whose translocation to the plasma membrane triggers Store Operated Ca2+ Entry (SOCE), and a subsequent rise in cytosolic Ca2+. Relatively little is known about SOCEs contribution to neuroendocrine cells; a neuronal sub-type that specializes in the secretion of neuropeptides (NPs) which ultimately regulate animal physiology and behavior. To investigate how SOCE regulates NPs, Drosophila development under nutrient restriction (NR) was used as the biological context. Genetic experiments identified the requirement of two SOCE-regulated NPs-corazonin (Crz) and short neuropeptide F (sNPF) - for the development of NR larvae to pupae and finally, adulthood. Overexpression of SOCE regulators was sufficient to rescue the development of NR larvae with reduced sNPF or Crz levels. To facilitate cellular investigations, a restricted set of neurons that produce sNPF and Crz, and are activated by NR, were identified. Immunohistochemistry on these neurons and mass spectrometric measurements of their projections showed that dSTIM regulates Crz and sNPF levels at steady state and in response to NR, likely by modulating their release. Genetically increasing neuronal output, in the background of reduced dSTIM, robustly rescued development of NR larvae. Because NP action fundamentally underpins how animals adapt to stimuli, regulation of NPs by STIM triggered SOCE is likely to be important. In situations where SOCE is altered, such as neurodegenerative diseases, this regulation may contribute to disease manifestation and progression.

developmental biology↗