View source for Longevity of insects with social castes

Social insects such as ants,<ref name="ants">Majoe, M., Libbrecht, R., Foitzik, S., & Nehring, V. (2021). Queen loss increases worker survival in leaf-cutting ants under paraquat-induced oxidative stress. Philosophical Transactions of the Royal Society B, 376(1823), 20190735. PMID: 33678018 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7938173 link] DOI: 10.1098/rstb.2019.0735</ref> bees,<ref name="bee">Shell, W. A., & Rehan, S. M. (2022). Social divergence: molecular pathways underlying castes and longevity in a facultatively eusocial small carpenter bee. Proceedings of the Royal Society B, 289(1971), 20212663.  PMID: 35317677 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8941392 link]  DOI: 10.1098/rspb.2021.2663</ref> and termites,<ref name="Termite">Li, Y. X., Ye, C. X., Su, J., Nabi, G., Su, X. H., & Xing, L. X. (2022). De Novo Transcriptome Assembly and Analysis of Longevity Genes Using Subterranean Termite (Reticulitermes chinensis) Castes. International Journal of Molecular Sciences, 23(21), 13660. PMID: 36362447 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9657995 link] DOI: 10.3390/ijms232113660</ref> have a distinct division of labor among individuals within their colonies. The colony is typically composed of a reproductive queen or queens and non-reproductive workers or soldier castes.<ref>Opachaloemphan, C., Yan, H., Leibholz, A., Desplan, C., & Reinberg, D. (2018). Recent advances in behavioral (epi) genetics in eusocial insects. Annual review of genetics, 52, 489.   PMID: 30208294 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6445553 link] DOI: 10.1146/annurev-genet-120116-024456</ref> Research has shown that there are significant differences in longevity between the queen and worker castes in many social insect species. In general, queens live much longer than workers, and any worker can become a queen given the appropriate environmental cues by turning on or off specific genes (i.e. via epigenetic mechanisms).<ref name="Epigenetic">Sieber, K. R., Dorman, T., Newell, N., & Yan, H. (2021). (Epi) genetic mechanisms underlying the evolutionary success of eusocial insects. Insects, 12(6), 498. PMID: 34071806 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8229086 link] DOI: 10.3390/insects12060498</ref> 

The difference in longevity of the social castes is thought to be related to the different roles that queens and workers play within the colony. Queens are responsible for reproducing and maintaining the colony, so they have evolved to live longer in order to increase their chances of reproducing.<ref name="Evolution">Remolina, S. C., & Hughes, K. A. (2008). Evolution and mechanisms of long life and high fertility in queen honey bees. Age, 30(2), 177-185.</ref> In contrast, workers are responsible for foraging food and caring for the colony's young, so they have evolved to have shorter lifespans as they expend a lot of energy and are more prone to injuries and predation.<ref name="Evolution" /> Additionally, queen ants and bees have a different hormonal regulation that allows them to live longer, and different gene expression profiles that increases their resistance to stress, while reducing their metabolism.

'''The fact that queens live many times longer than workers, despite sharing the same genome, provides a particularly useful model for understanding the epigenetic pathways and mechanisms that influence aging'''.<ref name="Epigenetic"/>

== Longevity of workers and queens ==

=== Bees ===
[[File:Laying worker bee.png|thumb|Laying worker bee.<ref>https://www.beeculture.com/laying-workers-happens-fix/</ref>]]
In hives, queen bees are normally the only female who reproduces, whereas the vast majority of bees are sterile females known as worker bees. Queen honeybees can live for several years, while workers typically only live for several months.<ref name="Evolution" /> 

Even in a normal hive, about 1% of workers have ovaries developed enough to lay eggs. A laying worker bee is a worker bee that lays unfertilized eggs, usually in the queenless colonies. In colonies of the neotropical stingless bee ''Scaptotrigona aff. postica,'' '''the lifespan of worker bees was about a third longer in hives without mated queens''' (known as non-queenright colonies).<ref name="stingless">dos Santos Conceição Lopes, B., Campbell, A. J., & Contrera, F. A. L. (2020). Queen loss changes behavior and increases longevity in a stingless bee. Behavioral Ecology and Sociobiology, 74, 1-9. DOI: [https://doi.org/10.1007/s00265-020-2811-8 10.1007/s00265-020-2811-8]</ref> 

The worker bees of this species substantially alter their behavior without mated queens, for example by spending more time inside the nest building brood cells rather than participating in more risky foraging behaviors, therefore causing an increase in their overall longevity. Workers also start to lay haploid eggs, allowing some direct reproduction by workers in the absence of a queen.<ref name="stingless" /> This phenomenons highlight the plasticity of longevity in honeybees depending on environmental stimuli.

=== Ants ===
[[File:Gamergate worker ant.jpg|thumb|Gamergate worker ant. Gamergates are worker ants that reproduce sexually and lay fertilized eggs that will develop as females.]]
Ants also display a remarkable plasticity in their longevity that can be regulated via epigenetic mechanisms.<ref name="Epigenetic" /> For instance, in the ant species ''L. niger'', queen ants live for 20 to 30 years, workers for 1 to 3 years and males for only a few weeks.<ref>Jemielity, S., Chapuisat, M., Parker, J. D., & Keller, L. (2005). Long live the queen: studying aging in social insects. Age, 27(3), 241-248. PMID: 23598656 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458492 link] DOI: 10.1007/s11357-005-2916-z</ref>

===== Gamergate ants =====
While in most ant species social castes are permanently established during the larval stage, adult ''Harpegnathos saltator'' workers can acquire a queen-like phenotype and become reproductive individuals called “gamergates”.<ref>Peeters, C., Liebig, J., & Hölldobler, B. (2000). Sexual reproduction by both queens and workers in the ponerine ant Harpegnathos saltator. Insectes Sociaux, 47, 325-332. https://doi.org/10.1007/PL00001724</ref> '''Workers that become gamergates also attain queen-like longevity, with a fivefold increase in average life span''' from 7 months to 3 years.<ref>Ghaninia, M., Haight, K., Berger, S. L., Reinberg, D., Zwiebel, L. J., Ray, A., & Liebig, J. (2017). Chemosensory sensitivity reflects reproductive status in the ant Harpegnathos saltator. Scientific reports, 7(1), 3732.  PMID: 28623371 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5473913 link] DOI: 10.1038/s41598-017-03964-7</ref>

In the ant ''Harpegnathos saltator'', aging workers exhibited a progressive loss of ensheathing glia cells, whereas in gamergates, they remained a larger proportion of total glia cells over the same time span. Consistent with this, old gamergates retained the ability to mount a response to neuronal damage, which was lost in old workers.<ref>Sheng, L., Shields, E. J., Gospocic, J., Glastad, K. M., Ratchasanmuang, P., Berger, S. L., ... & Bonasio, R. (2020). Social reprogramming in ants induces longevity-associated glia remodeling. Science advances, 6(34), eaba9869. PMID: 32875108 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7438095 link] DOI: 10.1126/sciadv.aba9869</ref>

It was found that gamergates have elevated expression of gamergate-specific gene encoding a truncated form of a heat shock factor (HSF) most similar to mammalian HSF2 (hsalHSF2). In workers, hsalHSF2 was bound to DNA only upon heat stress, whereas in gamergates, hsalHSF2 bound to DNA even in the absence of heat stress and was localized to gamergate-biased heat shock response (HSR) genes. Expression of hsalHSF2 in ''Drosophila melanogaster'' led to enhanced heat shock survival and extended life span in the absence of heat stress.<ref>Glastad, K. M., Roessler, J., Gospocic, J., Bonasio, R., & Berger, S. L. Long ant life span is maintained by a unique heat shock factor. Genes & development. 37(9-10), 398-417  doi: [https://doi.org/10.1101/gad.350250.122 10.1101/gad.350250.122]</ref>

===== Tapeworm-infected ants =====
[[File:Tapeworm-infected ants.jpg|thumb|Tapeworm-infected ant workers.<ref>https://www.beeculture.com/laying-workers-happens-fix/</ref>]]
Parasite infection induces multiple alterations in the adult workers. After infection, the survival of infected workers is increased compared to their uninfected nest-mates.<ref>Beros, S., Lenhart, A., Scharf, I., Negroni, M. A., Menzel, F., & Foitzik, S. (2021). Extreme lifespan extension in tapeworm-infected ant workers. Royal Society open science, 8(5), 202118. PMID: 34017599 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8131941 link] DOI: 10.1098/rsos.202118</ref> <ref name="presence">Stoldt, M., Klein, L., Beros, S., Butter, F., Jongepier, E., Feldmeyer, B., & Foitzik, S. (2021). Parasite presence induces gene expression changes in an ant host related to immunity and longevity. Genes, 12(1), 95. PMID: 33451085 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7828512 link] DOI: 10.3390/genes12010095</ref> A parasitic tapeworm greatly lengthens the lives of its ant hosts by secreting a rich cocktail (more than 250 proteins) of antioxidants and other compounds. 

Most secreted proteins from these parasitic tapeworms don't have any known annotated orthologs, which is indicative of potential novel functions and a long history of adaptation within this species interaction.<ref>Hartke, J., Ceron-Noriega, A., Stoldt, M., Sistermans, T., Kever, M., Fuchs, J., ... & Foitzik, S. (2022). What doesn't kill you makes you live longer-Longevity of a social host linked to parasite proteins. bioRxiv.     doi: [https://doi.org/10.1101/2022.12.23.521666 10.1101/2022.12.23.521666]</ref> 

A study found that both '''queens and infected workers express more of a gene called ''silver'' (carboxypeptidase D)''', compared to uninfected workers.<ref name="presence" /> Researchers previously '''linked the silver gene to an extended lifespan in fruit flies'''.<ref>Pauls, D., Hamarat, Y., Trufasu, L., Schendzielorz, T. M., Gramlich, G., Kahnt, J., ... & Wegener, C. (2019). Drosophila carboxypeptidase D (SILVER) is a key enzyme in neuropeptide processing required to maintain locomotor activity levels and survival rate. European Journal of Neuroscience, 50(9), 3502-3519. PMID: 31309630 DOI: 10.1111/ejn.14516</ref><ref>Carnes, M. U., Campbell, T., Huang, W., Butler, D. G., Carbone, M. A., Duncan, L. H., ... & Mackay, T. F. (2015). The genomic basis of postponed senescence in Drosophila melanogaster. PLoS One, 10(9), e0138569. PMID: 26378456 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4574564 link] DOI: 10.1371/journal.pone.0138569</ref>  However, a possible bias could be that infected workers do not engage in foraging outside the nest, and therefore have lower extrinsic mortality similar to queens, which also stay inside the nest.<ref name="presence" />

Another study<ref>Hartke, J., Ceron‐Noriega, A., Stoldt, M., Sistermans, T., Kever, M., Fuchs, J., ... & Foitzik, S. (2023). Long live the host! Proteomic analysis reveals possible strategies for parasitic manipulation of its social host. Molecular ecology, 32(21), 5877-5889.  https://doi.org/10.1111/mec.17155</ref> found two proteins exclusively in infected workers and healthy queens: '''fatty acid-binding protein 1''' and '''facilitated trehalose transporter Tret1-like''' - the protein that is responsible for transporting '''trehalose''', the main source of energy for insects, from the fat body into the haemolymph. One of trehalose's functions is the protection from different environmental stressors, such as oxidative stress. In addition, four unique proteins ('''death-associated protein 1''' (which positively regulates apoptosis);   '''chymotrypsin-2''' (shown to extend lifespan in Drosophila) and two uncharacterized proteins) were found in infected workers.

===== Wolbachia-infected ants =====
[[File:Pharaoh ants, with a worker (left) and queen (right)..jpg|thumb|Pharaoh ants, a worker (left) and queen (right).<ref>https://www.beeculture.com/laying-workers-happens-fix/</ref>]]
''Wolbachia'', a widespread maternally-inherited endosymbiotic bacteria, infects an estimated one-third of all ant species. In infected ''Monomorium pharaonis'' colonies, queens produce more eggs. Despite increased egg-laying by queens and higher colony-level metabolic rates, Wolbachia infection was not associated with decreased queen lifespan. In fact, in workers, which are obligately sterile, '''''Wolbachia'' infection was associated with longer lifespan'''.<ref>Rohini Singh, Sachin Suresh, Jennifer Fewell, Jon Harrison and Timothy Linksvayer (2023). Wolbachia-infected pharaoh ant colonies have higher egg production, metabolic rate, and worker survival. bioRxiv doi: [https://doi.org/10.1101/2023.01.31.526493 10.1101/2023.01.31.526493]</ref> Thus, increased egg-laying rates by queens and longer worker lifespans contribute to the higher growth rate and productivity that characterizes ''Wolbachia''-infected colonies. 

A role of metabolic provisioning of the host by endosymbionts has been demonstrated in several empirical studies. For example, Wolbachia can increase female fecundity in ''Drosophila'' flies by influencing iron homeostasis. In filarial nematodes, ''Wolbachia'' provisions the host with heme and riboflavin. Likewise, in a spider species, synthesis of fat and free amino acids has been shown to be improved by a ''Wolbachia'' infection, and in bedbugs, ''Wolbachia'' plays a nutritional role in vitamin B synthesis.<ref>Katlav, A., Nguyen, D. T., Morrow, J. L., Spooner-Hart, R. N., & Riegler, M. (2022). Endosymbionts moderate constrained sex allocation in a haplodiploid thrips species in a temperature-sensitive way. Heredity, 128(3), 169-177. PMID: 35115648 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8897473 link] DOI: 10.1038/s41437-022-00505-5</ref><ref>Katlav, A., Cook, J. M., & Riegler, M. (2022). Common endosymbionts affect host fitness and sex allocation via egg size provisioning. Proceedings of the Royal Society B, 289(1971), 20212582. PMID: 35350856 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8965393 link] DOI: 10.1098/rspb.2021.2582</ref>

=== Termites ===
Termites (Isoptera) are pale-coloured, soft-bodied eusocial insects living in complex societies that are characterized by a caste system in which despite the fact that all members in a termite colony have the same genetic background, few reproductively mature individuals (including a queen and a sperm-producing kings) reproduce and have extraordinarily long lives, while the large majority (non-reproductives, including workers and soldiers) perform tasks such as foraging, brooding and defence.<ref>Korb, J. (2007). Termites. Current Biology, 17(23), R995-R999. PMID: 18054770 DOI: 10.1016/j.cub.2007.10.033</ref><ref>Korb, J., Poulsen, M., Hu, H., Li, C., Boomsma, J. J., Zhang, G., & Liebig, J. (2015). A genomic comparison of two termites with different social complexity. Frontiers in Genetics, 6, 9.  PMID: 25788900 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4348803 link] DOI: 10.3389/fgene.2015.00009</ref>
Unlike hymenopteran social insects (ants, bees and wasps), where the sterile workers are all female, in termites both males and females can be workers.<ref>Revely, L., Sumner, S., & Eggleton, P. (2021). The plasticity and developmental potential of termites. Frontiers in Ecology and Evolution, 9, 552624.  https://doi.org/10.3389/fevo.2021.552624</ref> Furthermore, workers have unique flexibility in that a worker has the capability to develop into apterous neotenic reproductives that develop in the absence of reproductives to provide for continued growth of the colony.<ref>Miura, T., Scharf, M. E., Bignell, D. E., Roisin, Y., & Lo, N. (2011). Biology of termites: A modern synthesis. Molecular Basis Underlying Caste Differentiation in Termites pp 211–253  Roisin, Nathan Lo  DOI:[https://doi.org/10.1007/978-90-481-3977-4_9 10.1007/978-90-481-3977-4_9]</ref>

<ref>Harrison, M. C., Jongepier, E., Robertson, H. M., Arning, N., Bitard-Feildel, T., Chao, H., ... & Bornberg-Bauer, E. (2018). Hemimetabolous genomes reveal molecular basis of termite eusociality. Nature ecology & evolution, 2(3), 557-566. PMID: 29403074 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6482461 link] DOI: 10.1038/s41559-017-0459-1</ref>

Although the question of how termite queens, which exhibit (as well as ants and honeybees) extraordinary longevity and fertility in comparison with non-reproductive individuals has attracted much attention, the molecular mechanisms involved are not yet understood. <ref name="kings">Tasaki, E., Takata, M., & Matsuura, K. (2021). Why and how do termite kings and queens live so long?. Philosophical Transactions of the Royal Society B, 376(1823), 20190740. PMID: 33678028 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7938161 link] DOI: 10.1098/rstb.2019.0740</ref> It has been hypothesized that the queens of the termite ''Reticulitermes speratus'' have high level of oxidative stress resistance and suffer lower levels of oxidative damage than non-reproductive workers, due to the a highly efficient antioxidant system. In particular, queens had two times higher catalase activity and more than seven times higher expression levels of the catalase gene RsCAT1 than workers. Queens also showed higher expression levels of the peroxiredoxin gene RsPRX6.<ref>Tasaki, E., Kobayashi, K., Matsuura, K., & Iuchi, Y. (2017). An efficient antioxidant system in a long-lived termite queen. PLoS One, 12(1), e0167412.  PMID: 28076409 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5226355 link] DOI: 10.1371/journal.pone.0167412</ref>

An important antioxidant contributing to survival in termites is uric acid, which is reserved and used as a valuable nitrogen source. Uric acid was shown to be provided by workers to reproductive castes.<ref>Tong, R. L., Patel, J. S., Gordon, J. M., Lee, S. B., Chouvenc, T., & Su, N. Y. (2023). Exuviae Recycling Can Enhance Queen Oviposition and Colony Growth in Subterranean Termites (Blattodea: Rhinotermitidae: Coptotermes). Environmental Entomology, nvad009. PMID: 36773009 DOI: 10.1093/ee/nvad009</ref><ref>Tasaki, E., Sakurai, H., Nitao, M., Matsuura, K., & Iuchi, Y. (2017). Uric acid, an important antioxidant contributing to survival in termites. PLoS One, 12(6), e0179426.   PMID: 28609463 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5469489 link] DOI: 10.1371/journal.pone.0179426</ref> It was found that king- and queen-specific degradation of uric acid contributes to reproduction and longevity in the subterranean termite ''Reticulitermes speratus''. The urate oxidase gene (RsUAOX), which catalyses the first step of nitrogen recycling from stored uric acid, was highly expressed in mature kings and queens, and upregulated with differentiation into neotenic kings/queens.<ref> Konishi, T., Tasaki, E., Takata, M., & Matsuura, K. (2023). King-and queen-specific degradation of uric acid contributes to reproduction in termites. Proceedings of the Royal Society B, 290(1990), 20221942. PMID: 36598016 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9811635 link] (available on 2024-01-11) DOI: 10.1098/rspb.2022.1942</ref>

<ref>Ma, X. M., Li, Y. X., Zhang, H. X., Liu, Q., Su, X. H., & Xing, L. X. (2020). Transcriptomic evidence that insulin signalling pathway regulates the ageing of subterranean termite castes. Scientific Reports, 10(1), 1-13. PMID: 32424344 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7235038 link] DOI: 10.1038/s41598-020-64890-9</ref><ref>Séité, S., Harrison, M. C., Sillam-Dussès, D., Lupoli, R., Van Dooren, T. J., Robert, A., ... & Vasseur-Cognet, M. (2022). Lifespan prolonging mechanisms and insulin upregulation without fat accumulation in long-lived reproductives of a higher termite. Communications Biology, 5(1), 44. PMID: 35027667 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8758687 link] DOI: 10.1038/s42003-021-02974-6</ref>

The haploid genome sizes (C-values) of termites (Isoptera) ranged from 0.58 to 1.90 pg, (1pg = 978 Mb).<ref name="Long">Monroy Kuhn, J. M., Meusemann, K., & Korb, J. (2019). Long live the queen, the king and the commoner? Transcript expression differences between old and young in the termite Cryptotermes secundus. PLoS One, 14(2), e0210371. PMID: 30759161 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6373952 link] DOI: 10.1371/journal.pone.0210371</ref>

<ref>Harrison, M. C., Dohmen, E., George, S., Sillam-Dussès, D., Séité, S., & Vasseur-Cognet, M. (2022). Complex regulatory role of DNA methylation in caste-and age-specific expression of a termite. Open Biology, 12(7), 220047.PMID: 35857972 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9256085 link] DOI: 10.1098/rsob.220047</ref>

== Mechanisms of exceptional longevity ==
Some of the most prominent mechanisms thought to underly the extended longevity of queens are:

=== Endocrine signalling and insulin binding protein Imp-L2 ===
Imaginal morphogenesis protein‐Late 2 (Imp-L2), a putative homolog of vertebrate insulin-like growth factor (IGF)-binding protein 7 (IGFBP7), counteracts insulin/IGF signalling (IIS) in ''Drosophila'' and is essential for starvation resistance.<ref>Honegger, B., Galic, M., Köhler, K., Wittwer, F., Brogiolo, W., Hafen, E., & Stocker, H. (2008). Imp-L2, a putative homolog of vertebrate IGF-binding protein 7, counteracts insulin signaling in Drosophila and is essential for starvation resistance. Journal of biology, 7, 1-11. PMID: 18412985 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2323038 link] DOI: 10.1186/jbiol72</ref> It is known that genetic manipulations of pathway components that result in dampened IIS extend lifespan in worms, flies and mice, and ameliorate age-dependent functional decline in a [[FOXO longevity genes|FOXO]]-dependent manner.<ref>Piper, M. D. W., Selman, C., McElwee, J. J., & Partridge, L. (2008). Separating cause from effect: how does insulin/IGF signalling control lifespan in worms, flies and mice?. Journal of internal medicine, 263(2), 179-191. PMID: 18226095 DOI: 10.1111/j.1365-2796.2007.01906.x</ref>  Increased IMP-L2 levels in ''Drosophila'' similarly results in substantial lifespan extension.<ref>Alic, N., Hoddinott, M. P., Vinti, G., & Partridge, L. (2011). Lifespan extension by increased expression of the Drosophila homologue of the IGFBP7 tumour suppressor. Aging cell, 10(1), 137-147. PMID: 21108726 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3042147 link] DOI: 10.1111/j.1474-9726.2010.00653.x</ref>

It is assumed that in the process of egg-laying, some '''ant queens produce Imp-L2''', which suppresses the aging effects of insulin, so that they can consume all the additional food needed for their egg-laying without shortening their lives.<ref name="Imp">Yan, H., Opachaloemphan, C., Carmona-Aldana, F., Mancini, G., Mlejnek, J., Descostes, N., ... & Reinberg, D. (2022). Insulin signaling in the long-lived reproductive caste of ants. Science, 377(6610), 1092-1099. PMID: 36048960 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9526546 link] DOI: 10.1126/science.abm8767</ref> As is known, reducing the AKT (also known as Protein kinase B) branch of insulin signaling in the fat body and adipose tissue lengthens the life of ''Drosophila''.<ref>Cheng, X., Xie, M., Luo, L., Tian, Y., Yu, G., Wu, Q., ... & Yang, M. (2022). Inhibitor GSK690693 extends Drosophila lifespan via reduce AKT signaling pathway. Mechanisms of Ageing and Development, 202, 111633. PMID: 35065134 DOI: 10.1016/j.mad.2022.111633</ref> A study showed that strong AKT phosphorylation after insulin treatment was completely suppressed by Imp-L2.<ref name="Imp" />

=== Oxidative stress resistance ===
Vitellogenin (Vtg or Vg) is an egg yolk precursor produced by nearly all egg-laying females species. It is a source of nutrient and has additional roles in the scavenging of reactive oxygen species (ROS).<ref>Havukainen H, Münch D, Baumann A, Zhong S, Halskau Ø, Krogsgaard M, Amdam GV. Vitellogenin recognizes cell damage through membrane binding and shields living cells from reactive oxygen species. J Biol Chem. 2013 Sep 27;288(39):28369-81. doi: 10.1074/jbc.M113.465021.</ref> The '''expression of vitellogenin (Vg) appears to be linked to the queens increased resistance to stress'''.<ref>Seehuus SC, Norberg K, Gimsa U, Krekling T, Amdam GV (2006) Reproductive protein protects functionally sterile honey bee workers from oxidative stress. Proc Natl Acad Sci USA 103:962–967</ref> Bees with higher Vg levels had increased survival, while reducing the expression of Vg led to decreased lifespan. However, in queen honey bees, the expression of antioxidant genes is not necessarily increased nor is required for their long lifespan.<ref>Corona M, Hughes KA, Weaver DB, Robinson GE (2005) Gene expression patterns associated with queen honey bee longevity. Mech Ageing Dev 126:1230–1238</ref> 

=== Genes underlying the reproductive division of labor ===
For identifying differences in gene expression between queens and workers in eusocial insects pairs of the queen and worker RNA sequencing data were used to calculate the queen/worker ratio referred to as the QW ratio.<ref>Toga, K., & Bono, H. (2022). Meta-analysis of public RNA sequencing data of queens and workers in social Hymenoptera and termites. bioRxiv, 2022-11. Doi:[https://doi.org/10.1101/2022.11.20.516280 10.1101/2022.11.20.516280]</ref> Meta-analysis of RNA-seq data revealed 20 genes with differential expression between queens and workers. Among these genes, '''vitellogenin and vitellogenin receptors''', which are highly expressed in queens across many social insects. '''SPARC (secreted protein acidic and cysteine rich) was highly expressed in queens''', and '''RSG7 (regulator of G protein signaling 7) was highly expressed in workers'''. In mice, SPARC promotes insulin secretion via down-regulation of regulator of G protein 4 (RGS4) expression in pancreatic β cells. Functional analyses of the 20 genes retrieved from massive datasets of a large number of eusocial species may reveal in the future key regulators of the reproductive division of labor and and multiple differences in life expectancy.

When workers leave the natal colony or a queen dies, the expression of stage-specific genes is induced in workers, which leads to the differentiation of workers to reproductives.<ref name="Ras">Ye, C., Rasheed, H., Ran, Y., Yang, X., Xing, L., & Su, X. (2019). Transcriptome changes reveal the genetic mechanisms of the reproductive plasticity of workers in lower termites. BMC Genomics, 20.702. PMID: 31500567 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6734246 link] DOI: 10.1186/s12864-019-6037-y</ref> In particular the relative expression level of '''Ras''' in the isolated female workers (IWs) '''was 131-fold than that of the workers''', which indicated that Ras was especially overexpressed in workers in the absence of queens for activation of the Ras-ERK signalling pathway to drive the ovary development of isolated workers.<ref name="Ras" /> It was suggested that the signal transduction along the Ras-MAPK pathway crucially controls the reproductive plasticity of the workers and short-lived individuals can become long-lived individuals by the transition of castes.<ref name="Ras" />

==== Effective transposon regulation ====
For termites but not for hymenopterans, it was found that caste and age was associated with '''the expression of [[Transposons in aging|transposable elements (TEs)]]'''. While sterile workers who live only weeks had substantially higher TE activity, TE expression did not increase with age in the fat body of queens, despite a sevenfold increase in overall gene expression, due to a significant upregulation of the piRNA-pathway in 20-year-old queens of ''Macrotermes natalensis''.<ref>Post, F., Bornberg‐Bauer, E., Vasseur‐Cognet, M., & Harrison, M. C. (2023). More effective transposon regulation in fertile, long‐lived termite queens than in sterile workers. Molecular Ecology, 32(2), 369-380. PMID: 36320186 DOI: 10.1111/mec.16753</ref><ref>Elsner, D., Meusemann, K., & Korb, J. (2018). Longevity and transposon defense, the case of termite reproductives. Proceedings of the National Academy of Sciences, 115(21), 5504-5509. PMID: 29735660 PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6003524 link] DOI: 10.1073/pnas.1804046115</ref>

== References ==
<references />
[[Category:Main list]]
[[Category:Fundamentals]]