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Ewart KM, Ho SYW, Chowdhury AA, Jaya FR, Kinjo Y, Bennett J, Bourguignon T, Rose HA, Lo N. Pervasive relaxed selection in termite genomes. Proc Biol Sci 2024; 291:20232439. [PMID: 38772424 DOI: 10.1098/rspb.2023.2439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 05/02/2024] [Indexed: 05/23/2024] Open
Abstract
Genetic changes that enabled the evolution of eusociality have long captivated biologists. More recently, attention has focussed on the consequences of eusociality on genome evolution. Studies have reported higher molecular evolutionary rates in eusocial hymenopteran insects compared with their solitary relatives. To investigate the genomic consequences of eusociality in termites, we analysed nine genomes, including newly sequenced genomes from three non-eusocial cockroaches. Using a phylogenomic approach, we found that termite genomes have experienced lower rates of synonymous substitutions than those of cockroaches, possibly as a result of longer generation times. We identified higher rates of non-synonymous substitutions in termite genomes than in cockroach genomes, and identified pervasive relaxed selection in the former (24-31% of the genes analysed) compared with the latter (2-4%). We infer that this is due to reductions in effective population size, rather than gene-specific effects (e.g. indirect selection of caste-biased genes). We found no obvious signature of increased genetic load in termites, and postulate efficient purging of deleterious alleles at the colony level. Additionally, we identified genomic adaptations that may underpin caste differentiation, such as genes involved in post-translational modifications. Our results provide insights into the evolution of termites and the genomic consequences of eusociality more broadly.
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Affiliation(s)
- Kyle M Ewart
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Simon Y W Ho
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Al-Aabid Chowdhury
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Frederick R Jaya
- Ecology & Evolution, Research School of Biology, Australian National University, Acton, Australian Capital Territory, Australia
| | - Yukihiro Kinjo
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- Okinawa International University, Okinawa, Japan
| | - Juno Bennett
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Thomas Bourguignon
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Harley A Rose
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Nathan Lo
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
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Luitel B, Johnson AJ, Bulmer MS. Subterranean termites raise the alarm when their anti-fungal weapon falters. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2023; 111:1. [PMID: 38150102 DOI: 10.1007/s00114-023-01887-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 12/07/2023] [Accepted: 12/11/2023] [Indexed: 12/28/2023]
Abstract
Termicin is an anti-fungal defensin that is disseminated from termite salivary glands. The peptide appears to be critical for the elimination with mutual grooming (allogrooming) of pathogenic spores (conidia) that have attached to the insect cuticle. There has been a recent selective sweep for an advantageous variant of this peptide in the subterranean termite Reticulitermes flavipes. We tested the anti-mycotic activity of a recombinant termicin corresponding with this variant against the conidia of different Metarhizium fungal isolates from soil close to foraging R. flavipes workers. Termicin was most effective against isolates that had previously been shown to elicit a relatively weak alarm response, as indicated by brief bouts of rapid longitudinal oscillatory movement (LOM). These isolates that elicited weak alarm were also the deadliest apparently because the survival of termites exposed to the fungus depends on a strong social immune response (LOMs and allogrooming). The selective pressure for a single termicin variant may have been driven by the most dangerous isolates that elicit a weak behavioral response. The correlation between termicin anti-fungal activity and LOM suggests that pathogen-associated molecular patterns that affect termite recognition of conidial contamination and the onset of elevated allogrooming also affect the vulnerability of conidia to the disruption of their cell membranes by termicin.
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Affiliation(s)
- Bhawana Luitel
- Department of Biological Sciences, Towson University, 4101 Science Complex, 8000 York Rd, Towson, MD, 21252, USA
| | - Ajijola J Johnson
- Department of Biological Sciences, Towson University, 4101 Science Complex, 8000 York Rd, Towson, MD, 21252, USA
| | - Mark S Bulmer
- Department of Biological Sciences, Towson University, 4101 Science Complex, 8000 York Rd, Towson, MD, 21252, USA.
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Dong Y, Peng X, Hussain R, Niu T, Zhang H, Wang H, Xing LX, Wang R. Elevated expression of immune and DNA repair genes in mated queens and kings of the Reticulitermes chinensis termites. Exp Gerontol 2023; 178:112228. [PMID: 37271408 DOI: 10.1016/j.exger.2023.112228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/06/2023]
Abstract
Studies have identified that mating induces a series of physiological changes in animals. In this period, males tending to invest more energy, immune peptides, and other substances to reduce the cost of living for females. This results in lower survival rates in later life than females. Meanwhile, both males and females shorten lifespans due to reproduction. However, the reasons why termites' queens and kings are both extremely long-lived and highly fecund are unclear. Therefore, this study aimed to examine the effects of mating on the expression of immune and DNA repair genes for lifespan extension in termite queens and kings. Here, we reported that mated queens show relatively higher expression of immune genes (phenoloxidase, denfensin, termicin, transferrin), antioxidant genes (CAT, SOD), detoxification genes (GST, CYP450) than virgin queens in the Reticulitermes chinensis. In addition, mated kings also highly expressed these genes, except for termicin, transferrin, GST, and CYP450. After mating, both queens and kings significantly upregulated the expression of DNA repair genes (MLH1, BRCA1, XRCC3, RAD54-like). Mismatch repair genes (MMR) MSH2, MSH4, MSH6 were considerably increased in mated queens, while MSH4, MSH5, MSH6 were upregulated in mated kings. Our results suggest that mating increases the expression of immune and DNA repair genes in the termite queens and kings, and thus possibly improving their survival during reproductive span due to the omnipresent pathogens.
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Affiliation(s)
- Yanan Dong
- School of Ecology and Environment, Northwestern Polytechnical University, Xi'an 710072, China
| | - Xin Peng
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Riaz Hussain
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Tong Niu
- School of Ecology and Environment, Northwestern Polytechnical University, Xi'an 710072, China
| | - He Zhang
- Department of Pathology, Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou 450008, China
| | - Huan Wang
- School of Ecology and Environment, Northwestern Polytechnical University, Xi'an 710072, China
| | - Lian-Xi Xing
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Xi'an 710069, China.
| | - Ruiwu Wang
- School of Ecology and Environment, Northwestern Polytechnical University, Xi'an 710072, China.
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Bulmer MS, Franco BA, Biswas A, Greenbaum SF. Overcoming Immune Deficiency with Allogrooming. INSECTS 2023; 14:insects14020128. [PMID: 36835697 PMCID: PMC9965724 DOI: 10.3390/insects14020128] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 05/13/2023]
Abstract
Allogrooming appears to be essential in many social animals for protection from routine exposure to parasites. In social insects, it appears to be critical for the removal of pathogenic propagules from the cuticle before they can start an infectious cycle. For subterranean termites, this includes fungal spores commonly encountered in the soil, such as Metarhizium conidia, that can quickly germinate and penetrate the cuticle. We investigated whether there is a difference in reliance on social and innate immunity in two closely related subterranean termites for protection from fatal infections by two locally encountered Metarhizium species. Our results indicate that relatively weak innate immunity in one termite species is compensated by more sustained allogrooming. This includes enhanced allogrooming in response to concentrations of conidia that reflect more routine contamination of the cuticle as well as to heavy cuticular contamination that elicits a networked emergency response.
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Bechsgaard J, Jorgensen TH, Jønsson AK, Schou M, Bilde T. Impaired immune function accompanies social evolution in spiders. Biol Lett 2022; 18:20220331. [PMID: 36541093 PMCID: PMC9768628 DOI: 10.1098/rsbl.2022.0331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
An efficient immune system is essential to the survival of many animals. Sociality increases risk of pathogen transmission, which should select for enhanced immune function. However, two hypotheses instead predict a weakened immune function: relaxed selection caused by social immunity/protection, and reduced efficacy of selection due to inbreeding, reproductive skew and female bias in social species that reduce effective population size and accelerate genetic drift. We assessed the effect of social evolution on immune function in a comparative study of two social spider species and their closely related subsocial sister species (genus Stegodyphus). The haemolymph of social species was less efficient in inhibiting bacterial growth of the potentially pathogenic bacteria Bacillus subtilis than that of subsocial species. Reduced efficacy of selection in social species was supported by comparative genomic analysis showing substantially elevated non-synonymous substitutions in immune genes in one of the social species. We propose that impaired immune function results from reduced efficacy of selection because the evolution of sociality in spiders is accompanied by demographic processes that elevate genetic drift. Positive feedback between pathogen-induced local extinctions and the resulting elevation of genetic drift may further weaken responses to selection by pathogens, and threaten species persistence.
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Affiliation(s)
| | | | | | - Mads Schou
- Department of Biology, Lund University, Lund, Sweden
| | - Trine Bilde
- Department of Biology, Aarhus University, Aarhus, Denmark
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Rosengaus R, Traniello J, Bakker T. Sociality and disease: behavioral perspectives in ecological and evolutionary immunology. Behav Ecol Sociobiol 2022; 76:98. [PMID: 35821673 PMCID: PMC9263030 DOI: 10.1007/s00265-022-03203-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- Rebeca Rosengaus
- Department of Marine and Environmental Sciences, Northeastern University, Boston, MA 02115-5000 USA
| | - James Traniello
- Department of Biology, Boston University, 5 Cummington Mall, Boston, MA 02215 USA
| | - Theo Bakker
- Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, 53121 Bonn, Germany
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