6 NLR Function in Fungi as Revealed by the Study of Self/Non-self Recognition Systems

Abstract Trans-species polymorphism, meaning the presence of alleles in different species that are more similar to each other than they are to alleles in the same species, has been found at loci associated with vegetative incompatibility in filamentous fungi. If individuals differ at one or more of these loci (termed het for heterokaryon), they cannot form stable heterokaryons after vegetative fusion. At the het-c locus in Neurospora crassa and related species there is clear evidence of trans-species polymorphism: three alleles have persisted for ∼30 million years. We analyze a population genetic model of multilocus vegetative incompatibility and find the conditions under which trans-species polymorphism will occur. In the model, several unlinked loci determine the vegetative compatibility group (VCG) of an individual. Individuals of different VCGs fail to form productive heterokaryons, while those of the same VCG form viable heterokaryons. However, viable heterokaryon formation between individuals of the same VCG results in a loss in fitness, presumably via transfer of infectious agents by hyphal fusion or exploitation by aggressive genotypes. The result is a form of balancing selection on all loci affecting an individual's VCG. We analyze this model by making use of a Markov chain/strong selection, weak mutation (SSWM) approximation. We find that trans-species polymorphism of the type that has been found at the het-c locus is expected to occur only when the appearance of new incompatibility alleles is strongly constrained, because the rate of mutation to such alleles is very low, because the number of possible incompatibility alleles at each locus is restricted, or because the number of incompatibility loci is limited.

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To Fuse or Not to Fuse? An Evolutionary View of Self-Recognition Systems

Journal of Phylogenetics & Evolutionary Biology ◽

10.4172/2329-9002.1000103 ◽

2013 ◽

Vol 01 (01) ◽

Cited By ~ 5

Author(s):

Jeeremie Brusini

Keyword(s):

Self Recognition ◽

Evolutionary View ◽

Recognition Systems

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The conserved serine transporter SdaC moonlights to enable self recognition

Journal of Bacteriology ◽

10.1128/jb.00347-21 ◽

2021 ◽

Author(s):

Achala Chittor ◽

Karine A. Gibbs

Keyword(s):

Proteus Mirabilis ◽

Sequence Variation ◽

Interaction Network ◽

Bacterial Survival ◽

Ecological Constraints ◽

Collective Behaviors ◽

Open Conformation ◽

Self Recognition ◽

Recognition Protein ◽

Recognition Systems

Cells can use self recognition to achieve cooperative behaviors. Self-recognition genes are thought to principally evolve in tandem with partner self-recognition alleles. However, other constraints on protein evolution could exist. Here, we have identified an interaction outside of self-recognition loci that could constrain the sequence variation of a self-recognition protein. We show that during collective swarm expansion in Proteus mirabilis , self-recognition signaling co-opts SdaC, a serine transporter. Serine uptake is crucial for bacterial survival and colonization. Single-residue variants of SdaC reveal that self recognition requires an open conformation of the protein; serine transport is dispensable. A distant ortholog from Escherichia coli is sufficient for self recognition; however, a paralogous serine transporter, YhaO, is not. Thus, SdaC couples self recognition and serine transport, likely through a shared molecular interface. Self recognition proteins may follow the framework of a complex interaction network rather than an isolated two-protein system. Understanding molecular and ecological constraints on self-recognition proteins lays the groundwork for insights into the evolution of self recognition and emergent collective behaviors. Importance Bacteria can receive secret messages from kin during migration. For Proteus mirabilis , these messages are necessary for virulence in multi-species infections. We show that a serine transporter—conserved among gamma-enterobacteria– enables self recognition. Molecular co-option of nutrient uptake could limit the sequence variation of these message proteins. SdaC is the primary transporter for L-serine, a vital metabolite for colonization during disease. Unlike many self-recognition receptors, SdaC is sufficiently conserved between species to achieve recognition. The predicted open conformation is shared by transport and recognition. SdaC reveals the interdependence of communication and nutrient acquisition. As the broader interactions of self-recognition proteins are studied, features shared among microbial self-recognition systems, such as Dictyostelium spp. and Neurospora spp., could emerge.

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Analogies in the evolution of individual and social immunity

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2008.0166 ◽

2008 ◽

Vol 364 (1513) ◽

pp. 129-142 ◽

Cited By ~ 99

Author(s):

Sylvia Cremer ◽

Michael Sixt

Keyword(s):

Immune Responses ◽

Germ Line ◽

The Body ◽

Reproductive Tissue ◽

Defence Mechanisms ◽

Self Recognition ◽

Insect Societies ◽

The Social ◽

Recognition Systems ◽

Multicellular Organisms

We compare anti-parasite defences at the level of multicellular organisms and insect societies, and find that selection by parasites at these two organisational levels is often very similar and has created a number of parallel evolutionary solutions in the host's immune response. The defence mechanisms of both individuals and insect colonies start with border defences to prevent parasite intake and are followed by soma defences that prevent the establishment and spread of the parasite between the body's cells or the social insect workers. Lastly, germ line defences are employed to inhibit infection of the reproductive tissue of organisms or the reproductive individuals in colonies. We further find sophisticated self/non-self-recognition systems operating at both levels, which appear to be vital in maintaining the integrity of the body or colony as a reproductive entity. We then expand on the regulation of immune responses and end with a contemplation of how evolution may shape the different immune components, both within and between levels. The aim of this review is to highlight common evolutionary principles acting in disease defence at the level of both individual organisms and societies, thereby linking the fields of physiological and ecological immunology.

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Development of Self-Recognition Systems in Natural Killer Cells

Advances in Experimental Medicine and Biology - Mechanisms of Lymphocyte Activation and Immune Regulation VII ◽

10.1007/978-1-4615-5355-7_1 ◽

1998 ◽

pp. 1-12 ◽

Cited By ~ 7

Author(s):

P. V. Sivakumar ◽

N. S. Williams ◽

I. J. Puzanov ◽

J. D. Schatzle ◽

M. Bennett ◽

...

Keyword(s):

Natural Killer Cells ◽

Natural Killer ◽

Killer Cells ◽

Self Recognition ◽

Recognition Systems

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New self-identities evolve via point mutation in an invertebrate allorecognition gene

10.1101/2020.12.01.406256 ◽

2020 ◽

Author(s):

Aidan Huene ◽

Traci Chen ◽

Matthew L. Nicotra

Keyword(s):

Amino Acid ◽

Point Mutation ◽

Direct Evidence ◽

Transmembrane Protein ◽

Amino Acid Substitutions ◽

Functional Variation ◽

Hydractinia Symbiolongicarpus ◽

Self Recognition ◽

Two Component ◽

Recognition Systems

SummaryMany organisms use genetic self-recognition systems to distinguish themselves from other members of their species. To understand how new self-identities evolve, we studied Allorecognition 2 (Alr2), a self-recognition gene from the colonial cnidarian, Hydractinia symbiolongicarpus. Alr2 encodes a highly polymorphic transmembrane protein that discriminates self from non-self by selectively binding across cell membranes to other Alr2 proteins with identical or very similar sequences. Here, we show that new Alr2 proteins evolve by amino acid substitutions that immediately create isoforms with entirely novel binding specificities, or through intermediates with relaxed binding specificities. Our results also suggest a topology for homophilic interactions between Alr2 proteins. These results provide direct evidence for the generation and maintenance of functional variation at an allorecognition locus and reveal that one-component and two-component self-recognition systems evolve via different mechanisms.

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