Freeborn, L. | Search bioRxiv

bioRxiv2024

A bacterial NLR-related protein recognizes multiple unrelated phage triggers to sense infection

Immune systems must rapidly sense viral infections to initiate antiviral signaling, but sensing poses a unique biochemical challenge because viruses rapidly evolve to escape detection. Immune receptors must therefore detect conserved components or activities that are crucial to the viral lifecycle and cannot easily be altered. Here, we show that a bacterial NLR-related protein, bNACHT11, senses viral (phage) infection via direct interactions with multiple phage proteins that are unrelated in their sequences, structures, and functions, thereby limiting viral escape. A conserved surface on the bNACHT11 C-terminal sensor domain binds at least five distinct activators, and a cryo-electron microscopy structure reveals sensing of the protein backbone through {beta}-augmentation. Activator protein binding to bNACHT11 induced oligomerization and effector domain clustering, which limited phage infection by initiating programmed cell death through plasmolysis. These findings reveal a sophisticated immune strategy that counters the rapid evolution of viruses, with parallels to human and plant immune signaling.

microbiology↗

bioRxiv2024

Evolution and Diversification of the Aposematic Poison Frog, Oophaga pumilio, in Bocas del Toro

The aposematic strawberry poison frog, Oophaga pumilio, is an iconic model system for studying the evolution and maintenance of color variation. Through most of its range, this frog is red with blue limbs. However, frogs from the Bocas del Toro Province, Panama, show striking variance in color and pattern, both sympatrically and allopatrically. This observation contradicts standard models of the evolution of aposematism and has led to substantial speculation about its evolutionary and molecular causes. Since the enigma of O. pumilio phenotypic variation is partly unresolved because of its large, [~] 6.7 Gb genome, we here sequence exomes from 347 individuals from ten populations and map a number of genetic factors responsible for the color and pattern variation. The kit gene is the primary candidate underlying the blue-red polymorphism in Dolphin Bay, where an increase in melanosomes is correlated with blue coloration. Additionally, the ttc39b gene, a known enhancer of yellow-to-red carotenoid conversion in birds, is the primary factor behind the yellow-red polymorphism in the Bastimentos West area. The causal genetic regions show evidence of selective sweeps acting locally to spread the rare phenotype. Our analyses suggest an evolutionary model in which selection is driving the formation of new morphs in a dynamic system resulting from a trade-off between predation avoidance, intraspecific competition, and mate choice.

evolutionary biology↗