Biology subjects

Littlejohn, G. R.

Publications and source records attributed to Littlejohn, G. R..

3 recordsLinked to original sources

bioRxiv2025

Wherefore the magic? The evolutionary role of psilocybin in nature

Research into psychedelic compounds is in resurgence due to the exciting potential for their use in the treatment of psychiatric and mental health disorders. Despite this revival, remarkably little is known about their evolution. One of the most intriguing psychedelic compounds is psilocybin, the compound found in magic mushrooms and used in ritual ceremonies in Central America for generations. Associated with agaricomycete fungi of the genus Psilocybe, psilocybin acts in a similar way to the neurotransmitter serotonin, yet how and why natural selection favoured its biosynthesis remains unclear. Given the resemblance to serotonin, modulation of invertebrate behaviour for defence is a likely explanation, but neither this nor alternative hypotheses have ever been formally tested. Here, we show that Drosophila larvae exposed to extracts from Psilocybe mushrooms exhibit reduced survival, pupation rates, and inhibited locomotion. Adults exposed during development show reduced thorax and wing size, along with increased fluctuating asymmetry, indicating developmental stress. Conversely, mutants lacking 5HT2A receptors showed the same response to Psilocybe extracts as wild-type flies. Furthermore, DNA metabarcoding revealed that while Psilocybe semilanceata demonstrates a distinct invertebrate community compared to most other grassland fungi, it overlapped with the non-psychedelic species Mycena epipterygia. This study provides a crucial first step toward understanding the evolutionary role of psilocybin-producing fungi and provides a grounding for future research into the molecular mechanisms, ecological interactions and evolutionary origins of psychedelic compounds in nature.

ecology↗

bioRxiv2020

Chitosan inhibits septin-mediated plant infection by the rice blast fungus Magnaporthe oryzae in a Protein Kinase C and Nox1 NADPH oxidase-dependent manner

O_LIChitosan is a partially deacetylated linear polysaccharide composed of {beta}-1,4-linked units of D-glucosamine and N-acetyl glucosamine. As well as acting as a structural component of fungal cell walls, chitosan can be applied as a potent antifungal agent. However, the mode-of-action of chitosan in fungal pathogens is poorly understood. C_LIO_LIHere, we report that chitosan is effective for control of rice blast disease. Chitosan application impairs growth of the blast fungus Magnaporthe oryzae and has a pronounced effect on appressorium-mediated plant infection. Chitosan inhibits septin-mediated F-actin re-modelling at the appressorium pore, thereby preventing re-polarisation of the infection cell and rice leaf cuticle penetration. C_LIO_LIWe found that chitosan causes plasma membrane permeabilization of M. oryzae and affects NADPH oxidase-dependent synthesis of reactive oxygen species, essential for septin ring formation and fungal pathogenicity. Our data further show that the toxicity of chitosan to M. oryzae requires the protein kinase C-dependent cell wall integrity pathway and the Nox1 NADPH oxidase. A conditionally lethal, analogue (PP1)-sensitive mutant of Pkc1 is partially remediated for growth in the presence of chitosan and PP1, while {Delta}nox1 mutants increase their glucan/chitin cell wall ratio, rendering them resistant to chitosan. C_LIO_LITaken together, our data show that chitosan is a potent fungicide for control of the rice blast fungus which involves the cell wall integrity pathway, disrupts plasma membrane and inhibits septin-mediated plant infection. C_LI

plant biology↗

bioRxiv2020

A hierarchical transcriptional network controls appressorium-mediated plant infection by the rice blast fungus Magnaporthe oryzae

Rice blast is a pervasive and devastating disease that threatens rice production across the world. In spite of its importance to global food security, however, the underlying biology of plant infection by the blast fungus Magnaporthe oryzae remains poorly understood. In particular, it is unclear how the fungus elaborates a specialised infection cell, the appressorium, in response to surface signals from the rice leaf. Here, we report the identification of a network of temporally co-regulated transcription factors that act downstream of the Pmk1 mitogen-activated protein kinase pathway to regulate gene expression during appressorium-mediated plant infection. We have functionally characterised this network of transcription factors and demonstrated the operation of a hierarchical transcriptional control system. We show that this tiered regulatory mechanism involves Pmk1-dependent phosphorylation of the Hox7 homeobox transcription factor, which represses hyphal-associated gene expression and simultaneously induces major physiological changes required for appressorium development, including cell cycle arrest, autophagic cell death, turgor generation and melanin biosynthesis. Mst12 then regulates gene functions involved in septin-dependent cytoskeletal re-organisation, polarised exocytosis and effector gene expression necessary for plant tissue invasion.

microbiology↗