Light and the evolution of vision

Air channels create a directional light signal to regulate hypocotyl phototropism

In plants, light direction is perceived by the phototropin photoreceptors, which trigger directional growth responses known as phototropism. The formation of a phototropin activation gradient across a photosensitive organ initiates this response. However, the optical tissue properties that functionally contribute to phototropism remain unclear. In this work, we show that intercellular air channels limit light transmittance through various organs in several species. Air channels enhance light scattering in Arabidopsis hypocotyls, thereby steepening the light gradient. This is required for an efficient phototropic response in Arabidopsis and Brassica. We identified an embryonically expressed ABC transporter required for the presence of air channels in seedlings and a structure surrounding them. Our work provides insights into intercellular air space development or maintenance and identifies a mechanism of directional light sensing in plants.

Convergent TP53 loss and evolvability in cancer

Cancer cell populations evolve by a stepwise process involving natural selection of the fittest variants within a tissue ecosystem context and as modified by therapy. Genomic scrutiny of patient samples reveals an extraordinary diversity of mutational profiles both between patients with similar cancers and within the cancer cell population of individual patients. Does this signify highly divergent evolutionary trajectories or are there repetitive and predictable patterns?Major evolutionary innovations or adaptations in different species are frequently repeated, or convergent, reflecting both common selective pressures and constraints on optimal solutions. We argue this is true of evolving cancer cells, especially with respect to the TP53 gene. Functional loss variants in TP53 are the most common genetic change in cancer. We discuss the likely microenvironmental selective pressures involved and the profound impact this has on cell fitness, evolvability and probability of subsequent drug resistance.

A light-sensing system in the common ancestor of the fungi

Diverse light-sensing organs (i.e., eyes) have evolved across animals. Interestingly, several subcellular analogs have been found in eukaryotic microbes.¹ All of these systems have a common “recipe”: a light occluding or refractory surface juxtaposed to a membrane-layer enriched in type I rhodopsins.1, 2, 3, 4 In the fungi, several lineages have been shown to detect light using a diversity of non-homologous photo-responsive proteins.5, 6, 7 However, these systems are not associated with an eyespot-like organelle with one exception found in the zoosporic fungus Blastocladiella emersonii (Be).⁸Be possesses both elements of this recipe: an eyespot composed of lipid-filled structures (often called the side-body complex [SBC]), co-localized with a membrane enriched with a gene-fusion protein composed of a type I (microbial) rhodopsin and guanylyl cyclase enzyme domain (CyclOp-fusion protein).^8,9 Here, we identify homologous pathway components in four Chytridiomycota orders (Chytridiales, Synchytriales, Rhizophydiales, and Monoblepharidiales). To further explore the architecture of the fungal zoospore and its lipid organelles, we reviewed electron microscopy data (e.g., the works of Barr and Hartmann¹⁰ and Reichle and Fuller¹¹) and performed fluorescence-microscopy imaging of four CyclOp-carrying zoosporic fungal species, showing the presence of a variety of candidate eyespot-cytoskeletal ultrastructure systems. We then assessed the presence of canonical photoreceptors across the fungi and inferred that the last common fungal ancestor was able to sense light across a range of wavelengths using a variety of systems, including blue-green-light detection. Our data imply, independently of how the fungal tree of life is rooted, that the apparatus for a CyclOp-organelle light perception system was an ancestral feature of the fungi.

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A wide diversity of flagellated fungi possess the CyclOp light response circuit

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The same fungi possess the subcellular equipment to build lipid-based eyespots

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The last common ancestor of fungi possessed the CyclOp eyespot system

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The ancestral fungus could see a rainbow of light wavelengths

A new method for training creativity: narrative as an alternative to divergent thinking

Creativity is a major source of innovation, growth, adaptability, and psychological resilience, making it a top priority of governments, global corporations, educational institutions, and other organizations that collectively invest hundreds of millions of dollars annually into training. The current foundation of creativity training is the technique known as divergent thinking; yet for decades, concerns have been raised about the adequacy of divergent thinking: it is incongruent with the creative processes of children and most adult creatives, and it has failed to yield expected downstream results in creative production. In this article, we present an alternative approach to creativity training, based in neural processes different from those involved in divergent thinking and drawing upon a previously unused resource for creativity research: narrative theory. We outline a narrative theory of creativity training; illustrate with examples of training and assessment from our ongoing work with the U.S. Department of Defense, Fortune 50 companies, and graduate and professional schools; and explain how the theory can help fill prominent lacunae and gaps in existing creativity research, including the creativity of children, the psychological mechanisms of scientific and technological innovation, and the failure of computer artificial intelligence to replicate human creativity.

Transcriptional remodelling upon light removal in a model cnidarian: Losses and gains in gene expression

Organismal responses to light:dark cycles can result from two general processes: (a) direct response to light or (b) a free-running rhythm (i.e., a circadian clock). Previous research in cnidarians has shown that candidate circadian clock genes have rhythmic expression in the presence of diel lighting, but these oscillations appear to be lost quickly after removal of the light cue. Here, we measure whole-organism gene expression changes in 136 transcriptomes of the sea anemone Nematostella vectensis, entrained to a light:dark environment and immediately following light cue removal to distinguish two broadly defined responses in cnidarians: light entrainment and circadian regulation. Direct light exposure resulted in significant differences in expression for hundreds of genes, including more than 200 genes with rhythmic, 24-hr periodicity. Removal of the lighting cue resulted in the loss of significant expression for 80% of these genes after 1 day, including most of the hypothesized cnidarian circadian genes. Further, 70% of these candidate genes were phase-shifted. Most surprisingly, thousands of genes, some of which are involved in oxidative stress, DNA damage response and chromatin modification, had significant differences in expression in the 24 hr following light removal, suggesting that loss of the entraining cue may induce a cellular stress response. Together, our findings suggest that a majority of genes with significant differences in expression for anemones cultured under diel lighting are largely driven by the primary photoresponse rather than a circadian clock when measured at the whole animal level. These results provide context for the evolution of cnidarian circadian biology and help to disassociate two commonly confounded factors driving oscillating phenotypes.

Tissue-specific transcriptome analyses provide new insights into GPCR signalling in adult Schistosoma mansoni

Schistosomes are blood-dwelling trematodes with global impact on human and animal health. Because medical treatment is currently based on a single drug, praziquantel, there is urgent need for the development of alternative control strategies. The Schistosoma mansoni genome project provides a platform to study and connect the genetic repertoire of schistosomes to specific biological functions essential for successful parasitism. G protein-coupled receptors (GPCRs) form the largest superfamily of transmembrane receptors throughout the Eumetazoan phyla, including platyhelminths. Due to their involvement in diverse biological processes, their pharmacological importance, and proven druggability, GPCRs are promising targets for new anthelmintics. However, to identify candidate receptors, a more detailed understanding of the roles of GPCR signalling in schistosome biology is essential. An updated phylogenetic analysis of the S. mansoni GPCR genome (GPCRome) is presented, facilitated by updated genome data that allowed a more precise annotation of GPCRs. Additionally, we review the current knowledge on GPCR signalling in this parasite and provide new insights into the potential roles of GPCRs in schistosome reproduction based on the findings of a recent tissue-specific transcriptomic study in paired and unpaired S. mansoni. According to the current analysis, GPCRs contribute to gonad-specific functions but also to nongonad, pairing-dependent processes. The latter may regulate gonad-unrelated functions during the multifaceted male-female interaction. Finally, we compare the schistosome GPCRome to that of another parasitic trematode, Fasciola, and discuss the importance of GPCRs to basic and applied research. Phylogenetic analyses display GPCR diversity in free-living and parasitic platyhelminths and suggest diverse functions in schistosomes. Although their roles need to be substantiated by functional studies in the future, the data support the selection of GPCR candidates for basic and applied studies, invigorating the exploitation of this important receptor class for drug discovery against schistosomes but also other trematodes.