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. 2019 Jul 30;9(16):9129-9136.
doi: 10.1002/ece3.5460. eCollection 2019 Aug.

Suicidal Selection: Programmed Cell Death Can Evolve in Unicellular Organisms Due Solely to Kin Selection

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Free PMC article

Suicidal Selection: Programmed Cell Death Can Evolve in Unicellular Organisms Due Solely to Kin Selection

Anya E Vostinar et al. Ecol Evol. .
Free PMC article

Abstract

Abstract: Unicellular organisms can engage in a process by which a cell purposefully destroys itself, termed programmed cell death (PCD). While it is clear that the death of specific cells within a multicellular organism could increase inclusive fitness (e.g., during development), the origin of PCD in unicellular organisms is less obvious. Kin selection has been shown to help maintain instances of PCD in existing populations of unicellular organisms; however, competing hypotheses exist about whether additional factors are necessary to explain its origin. Those factors could include an environmental shift that causes latent PCD to be expressed, PCD hitchhiking on a large beneficial mutation, and PCD being simply a common pathology. Here, we present results using an artificial life model to demonstrate that kin selection can, in fact, be sufficient to give rise to PCD in unicellular organisms. Furthermore, when benefits to kin are direct-that is, resources provided to nearby kin-PCD is more beneficial than when benefits are indirect-that is, nonkin are injured, thus increasing the relative amount of resources for kin. Finally, when considering how strict organisms are in determining kin or nonkin (in terms of mutations), direct benefits are viable in a narrower range than indirect benefits.

Open research badges: This article has been awarded Open Data and Open Materials Badges. All materials and data are publicly accessible via the Open Science Framework at https://github.com/anyaevostinar/SuicidalAltruismDissertation/tree/master/LongTerm.

Keywords: artificial life; kin selection; programmed cell death.

Conflict of interest statement

None declared.

Figures

Figure 1
Figure 1
A simplified example of an Avida world. Half‐circles are unicells where color indicates differences in genomes. One unicell's internal hardware is shown, including CPU, memory, and a genome of program instructions
Figure 2
Figure 2
An example of a unicell undergoing programmed cell death. Each square represents a unicell. The number in each cell is a number of genetic differences between the unicell in that space and the focal unicell depicted as an explosion. Every unicell is a 2‐space radius (red line) is evaluated as kin or nonkin. Nonkin are marked with red X's. If the programmed cell death has direct benefit, unicells within the radius without a red X will receive the benefit. If the behavior has indirect benefit, unicells with red X's will be harmed
Figure 3
Figure 3
(a) When there is a direct benefit to kin, 12.52% of the population attempt to perform the programmed cell death behavior. However, when that benefit is removed, the behavior does not evolve into the population. (b) When there is an indirect benefit to kin, 7.11% of the population attempt to perform the programmed cell death behavior. However, when the indirect benefit is removed, the behavior does not evolve into the population
Figure 4
Figure 4
Percentage of population which performed programmed cell death when benefits to kin were direct or indirect with varying kin inclusivity levels. At direct‐pcd‐3, the programmed cell death behavior is used most frequently. For indirect benefits, a KIL 3 or lower leads to the most use of the behavior
Figure 5
Figure 5
The average number of surrounding unicells directly affected per programmed cell death event across varying kin inclusivity levels when trait first emerges. (a) When benefits are direct, direct‐pcd‐100 have the highest amount of surrounding kin during initial evolution of the trait, leading to the most initial benefit. (b) When benefits are indirect, nonkin unicells are directly affected and at indirect‐pcd‐0, the most surrounding unicells are considered nonkin and therefore each programmed cell death event has the largest effect
Figure 6
Figure 6
Number of cheating unicells, that is, unicells that are considered kin but do not contain the PCD instruction and therefore will never engage in the behavior. (a) While populations with direct‐pcd‐30 to 100 have a high initial benefit (Figure 5a), unicells without the PCD gene are considered kin throughout the experiment, decreasing the relative benefit of the PCD trait for unicells with the PCD gene. direct‐pcd‐3, however, enables unicells expressing the PCD trait to balance a high initial benefit with excluding unicells without the PCD gene after the initial emergence of the trait (cheaters). (b) At indirect‐pcd‐0, unicells without the PCD trait (cheaters) are prevented from invading completely throughout evolution. Unicells have no way of detecting presence of the PCD gene, the KIL requires unicells to use overall genetic difference as a proxy for the likelihood of another unicell having the PCD gene or not

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References

    1. Ackermann M., Stecher B., Freed N. E., Songhet P., Hardt W.‐D., & Doebeli M. (2008). Self‐destructive cooperation mediated by phenotypic noise. Nature, 454(7207), 987–990. - PubMed
    1. Beckmann B. E., & McKinley P. K. (2009). Evolving quorum sensing in digital organisms. In GECCO ’09: Proceedings of the 11th annual conference on genetic and evolutionary computation, pages 97–104. ACM Request Permissions.
    1. Berngruber T. W., Lion S., & Gandon S. (2013). Evolution of suicide as a defence strategy against pathogens in a spatially structured environment. Ecology Letters, 16(4), 446–453. - PubMed
    1. Bidle K. D. (2016). Programmed cell death in unicellular phytoplankton. Current Biology, 26(13), R594–R607. - PubMed
    1. Chao L., & Levin B. R. (1981). Structured habitats and the evolution of anticompetitor toxins in bacteria. Proceedings of the National Academy of Sciences of the United States of America, 78(10), 6324–6328. - PMC - PubMed

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