1
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Brülhart J, Süß A, Oettler J, Heinze J, Schultner E. Sex- and caste-specific developmental responses to juvenile hormone in an ant with maternal caste determination. J Exp Biol 2024; 227:jeb247396. [PMID: 38779857 DOI: 10.1242/jeb.247396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 05/16/2024] [Indexed: 05/25/2024]
Abstract
Juvenile hormone is considered to be a master regulator of polyphenism in social insects. In the ant Cardiocondyla obscurior, whether a female egg develops into a queen or a worker is determined maternally and caste-specific differentiation occurs in embryos, so that queens and workers can be distinguished in a non-invasive manner from late embryogenesis onwards. This ant also exhibits two male morphs - winged and wingless males. Here, we used topical treatment with juvenile hormone III and its synthetic analogue methoprene, a method that influences caste determination and differentiation in some ant species, to investigate whether hormone manipulation affects the development and growth of male, queen- and worker-destined embryos and larvae. We found no effect of hormone treatment on female caste ratios or body sizes in any of the treated stages, even though individuals reacted to heightened hormone availability with increased expression of krüppel-homolog 1, a conserved JH first-response gene. In contrast, hormone treatment resulted in the emergence of significantly larger males, although male morph fate was not affected. These results show that in C. obscurior, maternal caste determination leads to irreversible and highly canalized caste-specific development and growth.
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Affiliation(s)
- Jeanne Brülhart
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Anja Süß
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Jan Oettler
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Jürgen Heinze
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Eva Schultner
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
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2
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Peng T, Kennedy A, Wu Y, Foitzik S, Grüter C. Early life exposure to queen mandibular pheromone mediates persistent transcriptional changes in the brain of honey bee foragers. J Exp Biol 2024; 227:jeb247516. [PMID: 38725404 DOI: 10.1242/jeb.247516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 04/28/2024] [Indexed: 06/25/2024]
Abstract
Behavioural regulation in insect societies remains a fundamental question in sociobiology. In hymenopteran societies, the queen plays a crucial role in regulating group behaviour by affecting individual behaviour and physiology through modulation of worker gene expression. Honey bee (Apis mellifera) queens signal their presence via queen mandibular pheromone (QMP). While QMP has been shown to influence behaviour and gene expression of young workers, we know little about how these changes translate in older workers. The effects of the queen pheromone could have prolonged molecular impacts on workers that depend on an early sensitive period. We demonstrate that removal of QMP impacts long-term gene expression in the brain and antennae in foragers that were treated early in life (1 day post emergence), but not when treated later in life. Genes important for division of labour, learning, chemosensory perception and ageing were among those differentially expressed in the antennae and brain tissues, suggesting that QMP influences diverse physiological and behavioural processes in workers. Surprisingly, removal of QMP did not have an impact on foraging behaviour. Overall, our study suggests a sensitive period early in the life of workers, where the presence or absence of a queen has potentially life-long effects on transcriptional activity.
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Affiliation(s)
- Tianfei Peng
- Institute of Molecular and Organismic Evolution, Johannes Gutenberg University of Mainz, Biozentrum I, Hanns Dieter Hüsch Weg 15, 55128 Mainz, Germany
- College of Plant Science, Jilin University, Changchun 130062, PR China
| | - Anissa Kennedy
- Institute of Molecular and Organismic Evolution, Johannes Gutenberg University of Mainz, Biozentrum I, Hanns Dieter Hüsch Weg 15, 55128 Mainz, Germany
| | - Yongqiang Wu
- Institute of Molecular and Organismic Evolution, Johannes Gutenberg University of Mainz, Biozentrum I, Hanns Dieter Hüsch Weg 15, 55128 Mainz, Germany
| | - Susanne Foitzik
- Institute of Molecular and Organismic Evolution, Johannes Gutenberg University of Mainz, Biozentrum I, Hanns Dieter Hüsch Weg 15, 55128 Mainz, Germany
| | - Christoph Grüter
- Institute of Molecular and Organismic Evolution, Johannes Gutenberg University of Mainz, Biozentrum I, Hanns Dieter Hüsch Weg 15, 55128 Mainz, Germany
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3
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Ge J, Shalem Y, Ge Z, Liu J, Wang X, Bloch G. Integration of information from multiple sources drives and maintains the division of labor in bumble bee colonies. CURRENT OPINION IN INSECT SCIENCE 2023; 60:101115. [PMID: 37704097 DOI: 10.1016/j.cois.2023.101115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 08/12/2023] [Accepted: 09/08/2023] [Indexed: 09/15/2023]
Abstract
Bumble bees are eusocial bees in which the division of labor (DoL) in reproduction and in task performance changes during their annual lifecycle. The queen monopolizes reproduction in young colonies, but at later stages, some workers start to challenge the queen and lay their own unfertilized eggs. The division of colony maintenance and growth tasks relates to worker body size. Reproduction and task performance are regulated by multiple social signals of the queen, the workers, and the brood. Here, we review recent studies suggesting that bumble bees use multiple sources of information to establish and maintain DoL in both reproduction and in task performance. Juvenile hormone (JH) is an important neuroendocrine signal involved in the regulation of DoL in reproduction but not in worker task performance. The reliance on multiple signals facilitates flexibility in face of changes in the social and geophysical environment.
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Affiliation(s)
- Jin Ge
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, PR China; CAS Centre for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, PR China
| | - Yuval Shalem
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Zhuxi Ge
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, PR China; CAS Centre for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, PR China
| | - Jinpeng Liu
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, PR China; CAS Centre for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, PR China
| | - Xianhui Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, PR China; CAS Centre for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, PR China.
| | - Guy Bloch
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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4
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Wynants E, Van Dun C, Lenaerts N, Princen SA, Tuyttens E, Shpigler HY, Wenseleers T, Van Oystaeyen A. Uncovering the role of juvenile hormone in ovary development and egg laying in bumble bees. JOURNAL OF INSECT PHYSIOLOGY 2023; 150:104557. [PMID: 37625783 DOI: 10.1016/j.jinsphys.2023.104557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/18/2023] [Accepted: 08/21/2023] [Indexed: 08/27/2023]
Abstract
Juvenile hormone (JH) regulates developmental and physiological processes in insects. In bumble bees, the hormone acts as a gonadotropin that mediates ovary development, but the exact physiological pathways involved in ovary activation and subsequent egg laying are poorly understood. In this study, we examine how queen hibernation state, caste, and species impact the gonadotropic effect of JH in bumble bee queens through methoprene (JH analogue) application. We extend previous research by assessing queen egg laying and colony initiation, alongside ovary development. Furthermore, we compared sensitivity of workers of both species to the juvenile hormone's gonadotropic effect. In both bumble bee species, the ovaries of hibernated queens were developed five to six days after breaking diapause, regardless of methoprene treatment. By contrast, methoprene did have a stimulatory effect on ovary development in non-hibernated queens. The dose needed to obtain this effect was higher in B. impatiens. Methoprene did not have gonadotropic effects in callow workers of both species. These results indicate that the physiological effect of exogenous methoprene application varies according to species, caste and hibernation status. Interestingly, despite gonadotropic effects in non-hibernated queens, oviposition was not accelerated by JH. This suggests that JH alone is insufficient to induce egg laying and that an additional stimulus, which is naturally present in hibernated queens, is required. Consequently, our findings indicate that other physiological processes, beyond a rise in JH alone, are required for oviposition and colony initiation.
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Affiliation(s)
- Enya Wynants
- Biobest Group NV, Research and Development, 2260 Westerlo, Belgium
| | - Cédric Van Dun
- Laboratory of Socio-ecology and Social Evolution, University of Leuven, 3000 Leuven, Belgium
| | - Nancy Lenaerts
- Biobest Group NV, Research and Development, 2260 Westerlo, Belgium
| | - Sarah A Princen
- Biobest Group NV, Research and Development, 2260 Westerlo, Belgium
| | - Ella Tuyttens
- Biobest Group NV, Research and Development, 2260 Westerlo, Belgium
| | - Hagai Y Shpigler
- Department of Entomology, Agricultural Research Organization, The Volcani Institute, Rishon LeZion, Israel
| | - Tom Wenseleers
- Laboratory of Socio-ecology and Social Evolution, University of Leuven, 3000 Leuven, Belgium
| | - Annette Van Oystaeyen
- Biobest Group NV, Research and Development, 2260 Westerlo, Belgium; Laboratory of Socio-ecology and Social Evolution, University of Leuven, 3000 Leuven, Belgium.
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5
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Caminer MA, Libbrecht R, Majoe M, Ho DV, Baumann P, Foitzik S. Task-specific odorant receptor expression in worker antennae indicates that sensory filters regulate division of labor in ants. Commun Biol 2023; 6:1004. [PMID: 37783732 PMCID: PMC10545721 DOI: 10.1038/s42003-023-05273-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 08/22/2023] [Indexed: 10/04/2023] Open
Abstract
Division of labor (DOL) is a characteristic trait of insect societies, where tasks are generally performed by specialized individuals. Inside workers focus on brood or nest care, while others take risks by foraging outside. Theory proposes that workers have different thresholds to perform certain tasks when confronted with task-related stimuli, leading to specialization and consequently DOL. Workers are presumed to vary in their response to task-related cues rather than in how they perceive such information. Here, we test the hypothesis that DOL instead stems from workers varying in their efficiency to detect stimuli of specific tasks. We use transcriptomics to measure mRNA expression levels in the antennae and brain of nurses and foragers of the ant Temnothorax longispinosus. We find seven times as many genes to be differentially expressed between behavioral phenotypes in the antennae compared to the brain. Moreover, half of all odorant receptors are differentially expressed, with an overrepresentation of the 9-exon gene family upregulated in the antennae of nurses. Nurses and foragers thus apparently differ in the perception of their olfactory environment and task-related signals. Our study supports the hypothesis that antennal sensory filters predispose workers to specialize in specific tasks.
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Affiliation(s)
- Marcel A Caminer
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany.
| | - Romain Libbrecht
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
- Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS, University of Tours, Tours, France
| | - Megha Majoe
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | - David V Ho
- Institute of Developmental and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Peter Baumann
- Institute of Developmental and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
- Institute of Molecular Biology, Mainz, Germany
| | - Susanne Foitzik
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
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6
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Barkdull M, Moreau CS. Worker Reproduction and Caste Polymorphism Impact Genome Evolution and Social Genes Across the Ants. Genome Biol Evol 2023; 15:evad095. [PMID: 37243539 PMCID: PMC10287540 DOI: 10.1093/gbe/evad095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 05/16/2023] [Accepted: 05/23/2023] [Indexed: 05/29/2023] Open
Abstract
Eusocial insects are characterized by several traits, including reproductive division of labor and caste polymorphisms, which likely modulate genome evolution. Concomitantly, evolution may act on specific genes and pathways underlying these novel, sociality-associated phenotypes. Reproductive division of labor should increase the magnitude of genetic drift and reduce the efficacy of selection by reducing effective population size. Caste polymorphism has been associated with relaxed selection and may facilitate directional selection on caste-specific genes. Here, we use comparative analyses of 22 ant genomes to test how reproductive division of labor and worker polymorphism influence positive selection and selection intensity across the genome. Our results demonstrate that worker reproductive capacity is associated with a reduction in the degree of relaxed selection but is not associated with any significant change to positive selection. We find decreases in positive selection in species with polymorphic workers, but no increase in the degree of relaxed selection. Finally, we explore evolutionary patterns in specific candidate genes associated with our focal traits in eusocial insects. Two oocyte patterning genes previously implicated in worker sterility evolve under intensified selection in species with reproductive workers. Behavioral caste genes generally experience relaxed selection associated with worker polymorphism, whereas vestigial and spalt, both associated with soldier development in Pheidole ants, experience intensified selection in worker polymorphic species. These findings expand our understanding of the genetic mechanisms underlying elaborations of sociality. The impacts of reproductive division of labor and caste polymorphisms on specific genes illuminate those genes' roles in generating complex eusocial phenotypes.
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Affiliation(s)
- Megan Barkdull
- Department of Ecology & Evolutionary Biology, Cornell University
| | - Corrie S Moreau
- Department of Ecology & Evolutionary Biology, Cornell University
- Department of Entomology, Cornell University
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7
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Aguilar P, Bourgeois T, Maria A, Couzi P, Demondion E, Bozzolan F, Gassias E, Force E, Debernard S. Methoprene-tolerant and Krüppel homolog 1 are actors of juvenile hormone-signaling controlling the development of male sexual behavior in the moth Agrotis ipsilon. Horm Behav 2023; 150:105330. [PMID: 36791650 DOI: 10.1016/j.yhbeh.2023.105330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 02/01/2023] [Accepted: 02/06/2023] [Indexed: 02/15/2023]
Abstract
In insects, juvenile hormone (JH) is critical for the orchestration of male reproductive maturation. For instance, in the male moth, Agrotis ipsilon, the behavioral response and the neuronal sensitivity within the primary olfactory centers, the antennal lobes (ALs), to the female-emitted sex pheromone increase with fertility during adulthood and the coordination between these events is governed by JH. However, the molecular basis of JH action in the development of sexual behavior remains largely unknown. Here, we show that the expression of the paralogous JH receptors, Methoprene-tolerant 1 and 2 (Met1, Met2) and of the JH-inducible transcription factor, Krüppel homolog 1 (Kr-h1) within ALs raised from the third day of adult life and this dynamic is correlated with increased behavioral responsiveness to sex pheromone. Met1-, Met2- and Kr-h1-depleted sexually mature males exhibited altered sex pheromone-guided orientation flight. Moreover, injection of JH-II into young males enhanced the behavioral response to sex pheromone with increased AL Met1, Met2 and Kr-h1 mRNA levels. By contrast, JH deficiency suppressed the behavioral response to sex pheromone coupled with reduced AL Met1, Met2 and Kr-h1 mRNA levels in allatectomized old males and these inhibitions were compensated by an injection of JH-II in operated males. Our results demonstrated that JH acts through Met-Kr-h1 signaling pathway operating in ALs, to promote the pheromone information processing and consequently the display of sexual behavior in synchronization with fertility to optimize male reproductive fitness. Thus, this study provides insights into the molecular mechanisms underlying the hormonal regulation of reproductive behavior in insects.
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Affiliation(s)
- Paleo Aguilar
- Institute of Biology, University of Madrid, Pozuelo de Alarcon, 28223 Madrid, Spain
| | - Thomas Bourgeois
- Sorbonne Université, INRA, CNRS, UPEC, IRD, Univ. P7, Institute of Ecology and Environmental Sciences of Paris, 78026 Versailles, France
| | - Annick Maria
- Sorbonne Université, INRA, CNRS, UPEC, IRD, Univ. P7, Institute of Ecology and Environmental Sciences of Paris, 75005 Paris, France
| | - Philippe Couzi
- Sorbonne Université, INRA, CNRS, UPEC, IRD, Univ. P7, Institute of Ecology and Environmental Sciences of Paris, 78026 Versailles, France
| | - Elodie Demondion
- Sorbonne Université, INRA, CNRS, UPEC, IRD, Univ. P7, Institute of Ecology and Environmental Sciences of Paris, 78026 Versailles, France
| | - Françoise Bozzolan
- Sorbonne Université, INRA, CNRS, UPEC, IRD, Univ. P7, Institute of Ecology and Environmental Sciences of Paris, 75005 Paris, France
| | - Edmundo Gassias
- Institute of Biology, University of Madrid, Pozuelo de Alarcon, 28223 Madrid, Spain
| | - Evan Force
- Sorbonne Université, INRA, CNRS, UPEC, IRD, Univ. P7, Institute of Ecology and Environmental Sciences of Paris, 75005 Paris, France
| | - Stéphane Debernard
- Sorbonne Université, INRA, CNRS, UPEC, IRD, Univ. P7, Institute of Ecology and Environmental Sciences of Paris, 75005 Paris, France.
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8
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Cheng FP, Hu XF, Pan LX, Gong ZX, Qin KX, Li Z, Wang ZL. Transcriptome changes of Apis mellifera female embryos with fem gene knockout by CRISPR/Cas9. Int J Biol Macromol 2023; 229:260-267. [PMID: 36587640 DOI: 10.1016/j.ijbiomac.2022.12.229] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 12/11/2022] [Accepted: 12/15/2022] [Indexed: 12/31/2022]
Abstract
The sex of honey bees is decided by a regulatory cascade comprising of csd, fem and Amdsx. In order to further identify other genes involved in sex determination and differentiation of honey bees in the early stages of embryo development, the CRISPR/Cas9 method was used to knock out fem gene in the embryonic stage of diploid western honey bees, and RNA-seq was used to analyze gene expression changes in the embryo after fem knockout. Finally, we found that the bees had undergone gender changes due to fem knockout. A total of 155 differentially expressed genes (DEGs) were obtained, with 48 up-regulated and 107 down-regulated DEGs in the mutant group compared to the control group. Of them, many genes are related to sex development or differentiation. In addition, 1502 differentially expressed alternative splicing events (DEASEs) related to 1011 genes, including the main honey bee sex-determining genes csd, tra2, fem, and Amdsx, were identified between the mutant group and control group, indicating that fem regulates alternative splicing of a large number of downstream genes. Our results provide valuable clues for further investigating the molecular mechanism of sex determination and differentiation in honey bees.
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Affiliation(s)
- Fu-Ping Cheng
- Honeybee Research Institute, Jiangxi Agricultural University, Nanchang 330045, China; Jiangxi Province Key Laboratory of Honeybee Biology and Beekeeping, Nanchang 330045, PR China
| | - Xiao-Fen Hu
- Honeybee Research Institute, Jiangxi Agricultural University, Nanchang 330045, China; Jiangxi Province Key Laboratory of Honeybee Biology and Beekeeping, Nanchang 330045, PR China
| | - Lu-Xia Pan
- Honeybee Research Institute, Jiangxi Agricultural University, Nanchang 330045, China; Jiangxi Province Key Laboratory of Honeybee Biology and Beekeeping, Nanchang 330045, PR China
| | - Zhi-Xian Gong
- Honeybee Research Institute, Jiangxi Agricultural University, Nanchang 330045, China; Jiangxi Province Key Laboratory of Honeybee Biology and Beekeeping, Nanchang 330045, PR China
| | - Kai-Xin Qin
- Honeybee Research Institute, Jiangxi Agricultural University, Nanchang 330045, China; Jiangxi Province Key Laboratory of Honeybee Biology and Beekeeping, Nanchang 330045, PR China
| | - Zhen Li
- Honeybee Research Institute, Jiangxi Agricultural University, Nanchang 330045, China; Jiangxi Province Key Laboratory of Honeybee Biology and Beekeeping, Nanchang 330045, PR China
| | - Zi-Long Wang
- Honeybee Research Institute, Jiangxi Agricultural University, Nanchang 330045, China; Jiangxi Province Key Laboratory of Honeybee Biology and Beekeeping, Nanchang 330045, PR China.
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9
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Renard T, Gueydan C, Aron S. DNA methylation and expression of the egfr gene are associated with worker size in monomorphic ants. Sci Rep 2022; 12:21228. [PMID: 36481802 PMCID: PMC9732050 DOI: 10.1038/s41598-022-25675-4] [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] [Received: 08/18/2022] [Accepted: 12/02/2022] [Indexed: 12/13/2022] Open
Abstract
The reproductive division of labour is a hallmark of eusocial Hymenoptera. Females are either reproductive queens or non-reproductive workers. In ants, workers often display further task specialisation that is associated with variation in size and/or morphology. Because female polyphenism is typically under environmental control, it is thought epigenetic mechanisms (such as DNA methylation) play a central role since they mediate gene-by-environment interactions. Methylation of the growth-promoting gene epidermal growth factor receptor (egfr) was indeed shown to control worker size in a highly polymorphic ant. However, it remains unknown if egfr methylation could also regulate worker size in monomorphic species. By combining experimental pharmacology and molecular biology, we show that worker size is associated with egfr methylation in two monomorphic ants. Furthermore, we functionally demonstrate that EGFR signalling affects worker size. These results indicate that worker size regulation by egfr methylation has been mechanistically conserved in ants but remains unexploited in monomorphic species.
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Affiliation(s)
- Thibaut Renard
- grid.4989.c0000 0001 2348 0746Evolutionary Biology and Ecology, Université Libre de Bruxelles, Avenue F.D. Roosevelt, 50, 1050 Brussels, Belgium
| | - Cyril Gueydan
- grid.4989.c0000 0001 2348 0746Molecular Biology of the Gene, Université Libre de Bruxelles, Rue Prof. Jeener et Brachet, 12, 6041 Gosselies, Belgium
| | - Serge Aron
- grid.4989.c0000 0001 2348 0746Evolutionary Biology and Ecology, Université Libre de Bruxelles, Avenue F.D. Roosevelt, 50, 1050 Brussels, Belgium
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10
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He Q, Zhang Y. Kr-h1, a Cornerstone Gene in Insect Life History. Front Physiol 2022; 13:905441. [PMID: 35574485 PMCID: PMC9092015 DOI: 10.3389/fphys.2022.905441] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Accepted: 04/13/2022] [Indexed: 11/13/2022] Open
Abstract
Insect life cycle is coordinated by hormones and their downstream effectors. Krüppel homolog1 (Kr-h1) is one of the crucial effectors which mediates the actions of the two critical hormones of insects, the juvenile hormone (JH) and 20-hydroxyecdysone (20E). It is a transcription factor with a DNA-binding motif of eight C2H2 zinc fingers which is found to be conserved among insect orders. The expression of Kr-h1 is fluctuant during insect development with high abundance in juvenile instars and lower levels in the final instar and pupal stage, and reappearance in adults, which is governed by the coordination of JH, 20E, and miRNAs. The dynamic expression pattern of Kr-h1 is closely linked to its function in the entire life of insects. Over the past several years, accumulating studies have advanced our understanding of the role of Kr-h1 during insect development. It acts as a universal antimetamorphic factor in both hemimetabolous and holometabolous species by directly inhibiting the transcription of 20E signaling genes Broad-Complex (Br-C) and Ecdysone induced protein 93F (E93), and steroidogenic enzyme genes involved in ecdysone biosynthesis. Meanwhile, it promotes vitellogenesis and ovarian development in the majority of studied insects. In addition, Kr-h1 regulates insect behavioral plasticity and caste identity, neuronal morphogenesis, maturation of sexual behavior, as well as embryogenesis and metabolic homeostasis. Hence, Kr-h1 acts as a cornerstone regulator in insect life.
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Affiliation(s)
- Qianyu He
- Heilongjiang Provincial Key Laboratory of Environmental Microbiology and Recycling of Argo-Waste in Cold Region, College of Life Science and Biotechnology, Heilongjiang Bayi Agricultural University, Daqing, China
| | - Yuanxi Zhang
- Daqing Municipal Ecology and Environment Bureau, Daqing, China
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11
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Santos PKF, Galbraith DA, Starkey J, Amsalem E. The effect of the brood and the queen on early gene expression in bumble bee workers' brains. Sci Rep 2022; 12:3018. [PMID: 35194064 PMCID: PMC8863840 DOI: 10.1038/s41598-022-06715-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Accepted: 02/04/2022] [Indexed: 11/12/2022] Open
Abstract
Worker reproduction in social insects is often regulated by the queen, but can be regulated by the brood and nestmates, who may use different mechanisms to induce the same outcomes in subordinates. Analysis of brain gene expression patterns in bumble bee workers (Bombus impatiens) in response to the presence of the queen, the brood, both or neither, identified 18 differentially expressed genes, 17 of them are regulated by the queen and none are regulated by the brood. Overall, brain gene expression differences in workers were driven by the queen’s presence, despite recent studies showing that brood reduces worker egg laying and provides context to the queen pheromones. The queen affected important regulators of reproduction and brood care across insects, such as neuroparsin and vitellogenin, and a comparison with similar datasets in the honey bee and the clonal raider ant revealed that neuroparsin is differentially expressed in all species. These data emphasize the prominent role of the queen in regulating worker physiology and behavior. Genes that serve as key regulators of workers’ reproduction are likely to play an important role in the evolution of sociality.
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Affiliation(s)
- Priscila K F Santos
- Department of Entomology, Center for Chemical Ecology, Center for Pollinator Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA.
| | - David A Galbraith
- Department of Entomology, Center for Chemical Ecology, Center for Pollinator Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
| | - Jesse Starkey
- Department of Entomology, Center for Chemical Ecology, Center for Pollinator Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
| | - Etya Amsalem
- Department of Entomology, Center for Chemical Ecology, Center for Pollinator Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
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12
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Pandey A, Bloch G. Krüppel-homologue 1 Mediates Hormonally Regulated Dominance Rank in a Social Bee. BIOLOGY 2021; 10:biology10111188. [PMID: 34827180 PMCID: PMC8614866 DOI: 10.3390/biology10111188] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 12/23/2022]
Abstract
Dominance hierarchies are ubiquitous in invertebrates and vertebrates, but little is known on how genes influence dominance rank. Our gaps in knowledge are specifically significant concerning female hierarchies, particularly in insects. To start filling these gaps, we studied the social bumble bee Bombus terrestris, in which social hierarchies among females are common and functionally significant. Dominance rank in this bee is influenced by multiple factors, including juvenile hormone (JH) that is a major gonadotropin in this species. We tested the hypothesis that the JH responsive transcription factor Krüppel homologue 1 (Kr-h1) mediates hormonal influences on dominance behavior. We first developed and validated a perfluorocarbon nanoparticles-based RNA interference protocol for knocking down Kr-h1 expression. We then used this procedure to show that Kr-h1 mediates the influence of JH, not only on oogenesis and wax production, but also on aggression and dominance rank. To the best of our knowledge, this is the first study causally linking a gene to dominance rank in social insects, and one of only a few such studies on insects or on female hierarchies. These findings are important for determining whether there are general molecular principles governing dominance rank across gender and taxa.
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Affiliation(s)
- Atul Pandey
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA
- Correspondence: (A.P.); (G.B.)
| | - Guy Bloch
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- Correspondence: (A.P.); (G.B.)
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13
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Gospocic J, Glastad KM, Sheng L, Shields EJ, Berger SL, Bonasio R. Kr-h1 maintains distinct caste-specific neurotranscriptomes in response to socially regulated hormones. Cell 2021; 184:5807-5823.e14. [PMID: 34739833 DOI: 10.1016/j.cell.2021.10.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 07/13/2021] [Accepted: 10/07/2021] [Indexed: 10/19/2022]
Abstract
Behavioral plasticity is key to animal survival. Harpegnathos saltator ants can switch between worker and queen-like status (gamergate) depending on the outcome of social conflicts, providing an opportunity to study how distinct behavioral states are achieved in adult brains. Using social and molecular manipulations in live ants and ant neuronal cultures, we show that ecdysone and juvenile hormone drive molecular and functional differences in the brains of workers and gamergates and direct the transcriptional repressor Kr-h1 to different target genes. Depletion of Kr-h1 in the brain caused de-repression of "socially inappropriate" genes: gamergate genes were upregulated in workers, whereas worker genes were upregulated in gamergates. At the phenotypic level, loss of Kr-h1 resulted in the emergence of worker-specific behaviors in gamergates and gamergate-specific traits in workers. We conclude that Kr-h1 is a transcription factor that maintains distinct brain states established in response to socially regulated hormones.
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Affiliation(s)
- Janko Gospocic
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Urology and Institute of Neuropathology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Karl M Glastad
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Lihong Sheng
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Emily J Shields
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Urology and Institute of Neuropathology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Shelley L Berger
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Biology, University of Pennsylvania School of Arts and Sciences, Philadelphia, PA 19104, USA.
| | - Roberto Bonasio
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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14
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Kennedy A, Herman J, Rueppell O. Reproductive activation in honeybee ( Apis mellifera) workers protects against abiotic and biotic stress. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190737. [PMID: 33678021 DOI: 10.1098/rstb.2019.0737] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Social insect reproductives exhibit exceptional longevity instead of the classic trade-off between somatic maintenance and reproduction. Even normally sterile workers experience a significant increase in life expectancy when they assume a reproductive role. The mechanisms that enable the positive relation between the antagonistic demands of reproduction and somatic maintenance are unclear. To isolate the effect of reproductive activation, honeybee workers were induced to activate their ovaries. These reproductively activated workers were compared to controls for survival and gene expression patterns after exposure to Israeli Acute Paralysis Virus or the oxidative stressor paraquat. Reproductive activation increased survival, indicating better immunity and oxidative stress resistance. After qPCR analysis confirmed our experimental treatments at the physiological level, whole transcriptome analysis revealed that paraquat treatment significantly changed the expression of 1277 genes in the control workers but only two genes in reproductively activated workers, indicating that reproductive activation preemptively protects against oxidative stress. Significant overlap between genes that were upregulated by reproductive activation and in response to paraquat included prominent members of signalling pathways and anti-oxidants known to affect ageing. Thus, while our results confirm a central role of vitellogenin, they also point to other mechanisms to explain the molecular basis of the lack of a cost of reproduction and the exceptional longevity of social insect reproductives. Thus, socially induced reproductive activation preemptively protects honeybee workers against stressors, explaining their longevity. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'
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Affiliation(s)
- Anissa Kennedy
- Department of Biology, University of North Carolina Greensboro, 321 McIver Street, Greensboro, NC 27403, USA
| | - Jacob Herman
- Department of Biology, University of North Carolina Greensboro, 321 McIver Street, Greensboro, NC 27403, USA
| | - Olav Rueppell
- Department of Biology, University of North Carolina Greensboro, 321 McIver Street, Greensboro, NC 27403, USA
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15
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Collins DH, Wirén A, Labédan M, Smith M, Prince DC, Mohorianu I, Dalmay T, Bourke AFG. Gene expression during larval caste determination and differentiation in intermediately eusocial bumblebees, and a comparative analysis with advanced eusocial honeybees. Mol Ecol 2021; 30:718-735. [PMID: 33238067 PMCID: PMC7898649 DOI: 10.1111/mec.15752] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 11/11/2020] [Accepted: 11/16/2020] [Indexed: 12/19/2022]
Abstract
The queen‐worker caste system of eusocial insects represents a prime example of developmental polyphenism (environmentally‐induced phenotypic polymorphism) and is intrinsic to the evolution of advanced eusociality. However, the comparative molecular basis of larval caste determination and subsequent differentiation in the eusocial Hymenoptera remains poorly known. To address this issue within bees, we profiled caste‐associated gene expression in female larvae of the intermediately eusocial bumblebee Bombus terrestris. In B. terrestris, female larvae experience a queen‐dependent period during which their caste fate as adults is determined followed by a nutrition‐sensitive period also potentially affecting caste fate but for which the evidence is weaker. We used mRNA‐seq and qRT‐PCR validation to isolate genes differentially expressed between each caste pathway in larvae at developmental stages before and after each of these periods. We show that differences in gene expression between caste pathways are small in totipotent larvae, then peak after the queen‐dependent period. Relatively few novel (i.e., taxonomically‐restricted) genes were differentially expressed between castes, though novel genes were significantly enriched in late‐instar larvae in the worker pathway. We compared sets of caste‐associated genes in B. terrestris with those reported from the advanced eusocial honeybee, Apis mellifera, and found significant but relatively low levels of overlap of gene lists between the two species. These results suggest both the existence of low numbers of shared toolkit genes and substantial divergence in caste‐associated genes between Bombus and the advanced eusocial Apis since their last common eusocial ancestor.
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Affiliation(s)
- David H Collins
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | - Anders Wirén
- School of Biological Sciences, University of East Anglia, Norwich, UK.,School of Medical Sciences, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Marjorie Labédan
- School of Biological Sciences, University of East Anglia, Norwich, UK.,Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Michael Smith
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | - David C Prince
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | - Irina Mohorianu
- School of Biological Sciences, University of East Anglia, Norwich, UK.,Jeffrey Cheah Biomedical Centre, WT-MRC Cambridge Stem Cell Institute, Cambridge, UK
| | - Tamas Dalmay
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | - Andrew F G Bourke
- School of Biological Sciences, University of East Anglia, Norwich, UK
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16
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Shpigler HY, Herb B, Drnevich J, Band M, Robinson GE, Bloch G. Juvenile hormone regulates brain-reproduction tradeoff in bumble bees but not in honey bees. Horm Behav 2020; 126:104844. [PMID: 32860832 DOI: 10.1016/j.yhbeh.2020.104844] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 07/27/2020] [Accepted: 08/12/2020] [Indexed: 12/15/2022]
Abstract
Gonadotropic hormones coordinate processes in diverse tissues regulating animal reproductive physiology and behavior. Juvenile hormone (JH) is the ancient and most common gonadotropin in insects, but not in advanced eusocial honey bees and some ants. To start probing the evolutionary basis of this change, we combined endocrine manipulations, transcriptomics, and behavioral analyses to study JH regulated processes in a bumble bee showing a relatively simple level of eusociality. We found that in worker fat body, more JH-regulated genes were up- rather than down-regulated, and enriched for metabolic and biosynthetic pathways. This transcriptomic pattern is consistent with earlier evidence that JH is the major gonadotropin in bumble bees. In the brain, more JH-regulated genes were down- rather than up-regulated and enriched for protein turnover pathways. Brain ribosomal protein gene expression shows a similar trend of downregulation in dominant workers, which naturally have high JH titers. In other species, similar downregulation of protein turnover is found in aging brains or under stress, associated with compromised long-term memory and health. These findings suggest a previously unknown gonadotropin-mediated tradeoff. Analysis of published data reveals no such downregulation of protein turnover pathways in the brain of honey bee workers, which exhibit more complex eusociality and in which JH is not a gonadotropin but rather regulates division of labor. These results suggest that the evolution of complex eusociality in honey bees was associated with modifications in hormonal signalling supporting extended and extremely high fertility while reducing the ancient costs of high gonadotropin titers to the brain.
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Affiliation(s)
- Hagai Y Shpigler
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel; Carl R. Woese Institute for Genomic Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - Brian Herb
- Carl R. Woese Institute for Genomic Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - Jenny Drnevich
- High-Performance Biological Computing Group, Roy J Carver Biotechnology Center, The University of Illinois at Urbana-Champaign, USA
| | - Mark Band
- Roy J Carver Biotechnology Center, The University of Illinois at Urbana-Champaign, USA; Institute of Evolution, University of Haifa, Israel
| | - Gene E Robinson
- Carl R. Woese Institute for Genomic Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA; Entomology Department, The University of Illinois at Urbana-Champaign, USA; Neuroscience Program, The University of Illinois at Urbana-Champaign, USA
| | - Guy Bloch
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
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17
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Tsang SSK, Law STS, Li C, Qu Z, Bendena WG, Tobe SS, Hui JHL. Diversity of Insect Sesquiterpenoid Regulation. Front Genet 2020; 11:1027. [PMID: 33133135 PMCID: PMC7511761 DOI: 10.3389/fgene.2020.01027] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/11/2020] [Indexed: 12/11/2022] Open
Abstract
Insects are arguably the most successful group of animals in the world in terms of both species numbers and diverse habitats. The sesquiterpenoids juvenile hormone, methyl farnesoate, and farnesoic acid are well known to regulate metamorphosis, reproduction, sexual dimorphism, eusociality, and defense in insects. Nevertheless, different insects have evolved with different sesquiterpenoid biosynthetic pathway as well as products. On the other hand, non-coding RNAs such as microRNAs have been implicated in regulation of many important biological processes, and have recently been explored in the regulation of sesquiterpenoid production. In this review, we summarize the latest findings on the diversity of sesquiterpenoids reported in different groups of insects, as well as the recent advancements in the understanding of regulation of sesquiterpenoid production by microRNAs.
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Affiliation(s)
- Stacey S K Tsang
- Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Sean T S Law
- Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Chade Li
- Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Zhe Qu
- Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | | | - Stephen S Tobe
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Jerome H L Hui
- Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
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18
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Orlova M, Starkey J, Amsalem E. A small family business: synergistic and additive effects of the queen and the brood on worker reproduction in a primitively eusocial bee. J Exp Biol 2020; 223:jeb217547. [PMID: 31953359 DOI: 10.1242/jeb.217547] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 01/08/2020] [Indexed: 01/04/2023]
Abstract
The mechanisms that maintain reproductive division of labor in social insects are still incompletely understood. Most studies focus on the relationship between adults, overlooking another important stakeholder - the juveniles. Recent studies show that not only the queen but also the brood regulate worker reproduction. However, how the two coordinate to maintain reproductive monopoly remained unexplored. Here, we disentangled the roles of the brood and the queen in primitively eusocial bees (Bombus impatiens) by examining their separated and combined effects on worker behavioral, physiological and brain gene expression. We found that young larvae produce a releaser effect on workers, decreasing oviposition and aggression, while the queen produces both releaser and primer effects, modifying worker behavior and reproductive physiology. The expression of reproduction- and aggression-related genes was altered in the presence of both queen and brood but was stronger or the same in the presence of the queen. We identified two types of interactions between the queen and the brood in regulating worker reproduction: (1) synergistic interactions regulating worker physiology, where the combined effect of the queen and the brood on worker physiology was greater than their separate effects; (2) additive interactions, where the combined effect of the queen and the brood on worker behavior was similar to the sum of their separate effects. Our results suggest that the queen and the brood interact synergistically and additively to regulate worker behavior and reproduction, and this interaction exists at multiple regulatory levels.
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Affiliation(s)
- Margarita Orlova
- Department of Entomology, Center for Chemical Ecology, Center for Pollinator Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Jesse Starkey
- Department of Entomology, Center for Chemical Ecology, Center for Pollinator Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Etya Amsalem
- Department of Entomology, Center for Chemical Ecology, Center for Pollinator Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
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19
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Pandey A, Motro U, Bloch G. Juvenile hormone interacts with multiple factors to modulate aggression and dominance in groups of orphan bumble bee (Bombus terrestris) workers. Horm Behav 2020; 117:104602. [PMID: 31647921 DOI: 10.1016/j.yhbeh.2019.104602] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 09/16/2019] [Accepted: 09/19/2019] [Indexed: 02/07/2023]
Abstract
Juvenile hormone (JH) is a key regulator of insect development and reproduction. Given that JH commonly affects adult insect fertility, it has been hypothesized to also regulate behaviors such as dominance and aggression that are associated with reproduction. We tested this hypothesis in the bumble bee Bombus terrestris for which JH has been shown to be the major gonadotropin. We used the allatoxin Precocene-I (P-I) to reduce hemolymph JH titers and replacement therapy with the natural JH to revert this effect. In small orphan groups of workers with similar body size but mixed treatment, P-I treated bees showed lower aggressiveness, oogenesis, and dominance rank compared with control and replacement therapy treated bees. In similar groups in which all bees were treated similarly, there was a clear dominance hierarchy, even in P-I and replacement therapy treatment groups in which the bees showed similar levels of ovarian activation. In a similar experiment in which bees differed in body size, larger bees were more likely to be dominant despite their similar JH treatment and ovarian state. In the last experiment, we show that JH manipulation does not affect dominance rank in groups that had already established a stable dominance hierarchy. These findings solve previous ambiguities concerning whether or not JH affects dominance in bumble bees. JH positively affects dominance, but bees with similar levels of JH can nevertheless establish dominance hierarchies. Thus, multiple factors including JH, body size, and previous experience affect dominance and aggression in social bumble bees.
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Affiliation(s)
- Atul Pandey
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Israel
| | - Uzi Motro
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Israel
| | - Guy Bloch
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Israel.
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20
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Li KL, Yuan SY, Nanda S, Wang WX, Lai FX, Fu Q, Wan PJ. The Roles of E93 and Kr-h1 in Metamorphosis of Nilaparvata lugens. Front Physiol 2018; 9:1677. [PMID: 30524315 PMCID: PMC6262030 DOI: 10.3389/fphys.2018.01677] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 11/08/2018] [Indexed: 11/21/2022] Open
Abstract
Metamorphosis is a crucial process in insect development. Ecdysone-induced protein 93 (E93) is a determinant that promotes adult metamorphosis in both hemimetabolous and holometabolous insects. Krüppel-homolog 1 (Kr-h1), an early juvenile hormone (JH)-inducible gene, participates in JH signaling pathway controlling insect metamorphosis. In the current study, an E93 cDNA (NlE93) and two Kr-h1 cDNA variants (NlKr-h1-a and NlKr-h1-b) were cloned from Nilaparvata lugens (Stål), one of the most destructive hemimetabolous insect pests on rice. Multiple sequence alignment showed that both NlE93 and NlKr-h1 share high identity with their orthologs from other insects. The expression patterns revealed that decreasing NlKr-h1 mRNA levels were correlated with increasing NlE93 mRNA levels and vice versa. Moreover, RNA interference (RNAi) assays showed that the knockdown of one of the two genes resulted in significantly upregulated expression of the other. Correspondingly, phenotypical observation of the RNAi insects revealed that depletion of NlE93 prevented nymph–adult transition (causing a supernumerary nymphal instar), while depletion of NlKr-h1 triggered precocious formation of incomplete adult features. The results suggest that Nlkr-h1 and NlE93 are mutual repressors, fitting into the MEKRE93 pathway. The balance between these two genes plays a critical role in the metamorphosis of N. lugens determining the proper timing for activating metamorphosis during the nymphal stage.
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Affiliation(s)
- Kai Long Li
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China.,Hunan Institute of Food Quality Supervision Inspection and Research, Changsha, China
| | - San Yue Yuan
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
| | - Satyabrata Nanda
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
| | - Wei Xia Wang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
| | - Feng Xiang Lai
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
| | - Qiang Fu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
| | - Pin Jun Wan
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
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21
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Chandra V, Fetter-Pruneda I, Oxley PR, Ritger AL, McKenzie SK, Libbrecht R, Kronauer DJC. Social regulation of insulin signaling and the evolution of eusociality in ants. Science 2018; 361:398-402. [PMID: 30049879 PMCID: PMC6178808 DOI: 10.1126/science.aar5723] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 04/01/2018] [Accepted: 05/30/2018] [Indexed: 12/15/2022]
Abstract
Queens and workers of eusocial Hymenoptera are considered homologous to the reproductive and brood care phases of an ancestral subsocial life cycle. However, the molecular mechanisms underlying the evolution of reproductive division of labor remain obscure. Using a brain transcriptomics screen, we identified a single gene, insulin-like peptide 2 (ilp2), which is always up-regulated in ant reproductives, likely because they are better nourished than their nonreproductive nestmates. In clonal raider ants (Ooceraea biroi), larval signals inhibit adult reproduction by suppressing ilp2, thus producing a colony reproductive cycle reminiscent of ancestral subsociality. However, increasing ILP2 peptide levels overrides larval suppression, thereby breaking the colony cycle and inducing a stable division of labor. These findings suggest a simple model for the origin of ant eusociality via nutritionally determined reproductive asymmetries potentially amplified by larval signals.
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Affiliation(s)
- Vikram Chandra
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Ingrid Fetter-Pruneda
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Peter R Oxley
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
- Samuel J. Wood Library, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Amelia L Ritger
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Sean K McKenzie
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland
| | - Romain Libbrecht
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany
| | - Daniel J C Kronauer
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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22
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Cardoso-Júnior CAM, Silva RP, Borges NA, de Carvalho WJ, Walter SL, Simões ZLP, Bitondi MMG, Ueira Vieira C, Bonetti AM, Hartfelder K. Methyl farnesoate epoxidase (mfe) gene expression and juvenile hormone titers in the life cycle of a highly eusocial stingless bee, Melipona scutellaris. JOURNAL OF INSECT PHYSIOLOGY 2017; 101:185-194. [PMID: 28800885 DOI: 10.1016/j.jinsphys.2017.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 06/07/2023]
Abstract
In social insects, juvenile hormone (JH) has acquired novel functions related to caste determination and division of labor among workers, and this is best evidenced in the honey bee. In contrast to honey bees, stingless bees are a much more diverse group of highly eusocial bees, and the genus Melipona has long called special attention due to a proposed genetic mechanism of caste determination. Here, we examined methyl farnesoate epoxidase (mfe) gene expression, encoding an enzyme relevant for the final step in JH biosynthesis, and measured the hemolymph JH titers for all life cycle stages of Melipona scutellaris queens and workers. We confirmed that mfe is exclusively expressed in the corpora allata. The JH titer is high in the second larval instar, drops in the third, and rises again as the larvae enter metamorphosis. During the pupal stage, mfe expression is initialy elevated, but then gradually drops to low levels before adult emergence. No variation was, however, seen in the JH titer. In adult virgin queens, mfe expression and the JH titer are significantly elevated, possibly associated with their reproductive potential. For workers we found that JH titers are lower in foragers than in nurse bees, while mfe expression did not differ. Stingless bees are, thus, distinct from honey bee workers, suggesting that they have maintained the ancestral gonadotropic function for JH. Hence, the physiological circuitries underlying a highly eusocial life style may be variable, even within a monophyletic clade such as the corbiculate bees.
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Affiliation(s)
- Carlos Antônio Mendes Cardoso-Júnior
- Departamento de Biologia Celular, Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, 14049-900 Ribeirão Preto, SP, Brazil.
| | - Renato Pereira Silva
- Departmento de Genética e Bioquímica, Universidade Federal de Uberlândia, Av. Pará 1720, 38400-902 Uberlândia, MG, Brazil.
| | - Naiara Araújo Borges
- Departmento de Genética e Bioquímica, Universidade Federal de Uberlândia, Av. Pará 1720, 38400-902 Uberlândia, MG, Brazil.
| | - Washington João de Carvalho
- Departmento de Genética e Bioquímica, Universidade Federal de Uberlândia, Av. Pará 1720, 38400-902 Uberlândia, MG, Brazil.
| | - S Leal Walter
- Department of Molecular and Cellular Biology, College of Biological Sciences University of California at Davis, One Shields Ave., Davis, CA 95616, USA.
| | - Zilá Luz Paulino Simões
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirãp Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
| | - Marcia Maria Gentile Bitondi
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirãp Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
| | - Carlos Ueira Vieira
- Departmento de Genética e Bioquímica, Universidade Federal de Uberlândia, Av. Pará 1720, 38400-902 Uberlândia, MG, Brazil.
| | - Ana Maria Bonetti
- Departmento de Genética e Bioquímica, Universidade Federal de Uberlândia, Av. Pará 1720, 38400-902 Uberlândia, MG, Brazil.
| | - Klaus Hartfelder
- Departamento de Biologia Celular, Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, 14049-900 Ribeirão Preto, SP, Brazil.
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Abstract
Reproduction in social insect societies reflects a delicate balance between cooperation and conflict over offspring production, and worker reproduction is widespread even in species showing strong reproductive skew in favor of the queen. To navigate these conflicts, workers are predicted to develop the means to estimate the queen's fecundity - potentially through behavioral and/or chemical cues - and to adjust their reproduction to maximize their fitness. Here, we introduced bumble bee, Bombus impatiens, workers to queens of different mating and reproductive status and examined worker reproduction and expression levels of two genes which were previously shown to be sensitive to the presence of the queen, vitellogenin and Krüppel-homolog 1. We further explored whether the queen's chemical secretion alone is sufficient to regulate worker reproduction, aggression and gene expression. We found that worker ovary activation was inhibited only in the presence of egg-laying queens, regardless of their mating status. Workers reared in the presence of newly-mated queens showed intermediate vitellogenin expression levels relative to workers reared with mated egg-laying and virgin queens. However, none of the whole-body chemical extracts of any of the queen treatment groups affected ovary activation, aggressive behavior, or gene expression in workers. Our findings indicate that only the presence of a freely-behaving, egg-laying queen can fully inhibit worker reproduction. It remains to be determined if workers detect differences in queen mating status and fecundity through differences in the queens' behavior alone or through the queen's behavior in concert with fertility signals.
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Jedlička P, Ernst UR, Votavová A, Hanus R, Valterová I. Gene Expression Dynamics in Major Endocrine Regulatory Pathways along the Transition from Solitary to Social Life in a Bumblebee, Bombus terrestris. Front Physiol 2016; 7:574. [PMID: 27932998 PMCID: PMC5121236 DOI: 10.3389/fphys.2016.00574] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Accepted: 11/10/2016] [Indexed: 01/28/2023] Open
Abstract
Understanding the social evolution leading to insect eusociality requires, among other, a detailed insight into endocrine regulatory mechanisms that have been co-opted from solitary ancestors to play new roles in the complex life histories of eusocial species. Bumblebees represent well-suited models of a relatively primitive social organization standing on the mid-way to highly advanced eusociality and their queens undergo both, a solitary and a social phase, separated by winter diapause. In the present paper, we characterize the gene expression levels of major endocrine regulatory pathways across tissues, sexes, and life-stages of the buff-tailed bumblebee, Bombus terrestris, with special emphasis on critical stages of the queen's transition from solitary to social life. We focused on fundamental genes of three pathways: (1) Forkhead box protein O and insulin/insulin-like signaling, (2) Juvenile hormone (JH) signaling, and (3) Adipokinetic hormone signaling. Virgin queens were distinguished by higher expression of forkhead box protein O and downregulated insulin-like peptides and JH signaling, indicated by low expression of methyl farnesoate epoxidase (MFE) and transcription factor Krüppel homolog 1 (Kr-h1). Diapausing queens showed the expected downregulation of JH signaling in terms of low MFE and vitellogenin (Vg) expressions, but an unexpectedly high expression of Kr-h1. By contrast, reproducing queens revealed an upregulation of MFE and Vg together with insulin signaling. Surprisingly, the insulin growth factor 1 (IGF-1) turned out to be a queen-specific hormone. Workers exhibited an expression pattern of MFE and Vg similar to that of reproducing queens. Males were characterized by high Kr-h1 expression and low Vg level. The tissue comparison unveiled an unexpected resemblance between the fat body and hypopharyngeal glands across all investigated genes, sexes, and life stages.
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Affiliation(s)
- Pavel Jedlička
- Department of Chemistry of Social Insects, The Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences Prague, Czechia
| | - Ulrich R Ernst
- Department of Chemistry of Social Insects, The Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences Prague, Czechia
| | | | - Robert Hanus
- Department of Chemistry of Social Insects, The Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences Prague, Czechia
| | - Irena Valterová
- Research Group of Infochemicals, The Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences Prague, Czechia
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25
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Padilla M, Amsalem E, Altman N, Hefetz A, Grozinger CM. Chemical communication is not sufficient to explain reproductive inhibition in the bumblebee Bombus impatiens. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160576. [PMID: 27853577 PMCID: PMC5099002 DOI: 10.1098/rsos.160576] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 09/12/2016] [Indexed: 05/29/2023]
Abstract
Reproductive division of labour is a hallmark of eusociality, but disentangling the underlying proximate mechanisms can be challenging. In bumblebees, workers isolated from the queen can activate their ovaries and lay haploid, male eggs. We investigated if volatile, contact, visual or behavioural cues produced by the queen or brood mediate reproductive dominance in Bombus impatiens. Exposure to queen-produced volatiles, brood-produced volatiles and direct contact with pupae did not reduce worker ovary activation; only direct contact with the queen could reduce ovary activation. We evaluated behaviour, physiology and gene expression patterns in workers that were reared in chambers with all stages of brood and a free queen, caged queen (where workers could contact the queen, but the queen was unable to initiate interactions) or no queen. Workers housed with a caged queen or no queen fully activated their ovaries, whereas ovary activation in workers housed with a free queen was completely inhibited. The caged queen marginally reduced worker aggression and expression of an aggression-associated gene relative to queenless workers. Thus, queen-initiated behavioural interactions appear necessary to establish reproductive dominance. Queen-produced chemical cues may function secondarily in a context-specific manner to augment behavioural cues, as reliable or honest signal.
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Affiliation(s)
- Mario Padilla
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Etya Amsalem
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Naomi Altman
- Department of Statistics, Huck Institutes of Life Sciences, Clinical and Translational Sciences Institute, The Pennsylvania State University, University Park, PA 16802, USA
| | - Abraham Hefetz
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Christina M. Grozinger
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, The Pennsylvania State University, University Park, PA 16802, USA
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26
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Shpigler HY, Siegel AJ, Huang ZY, Bloch G. No effect of juvenile hormone on task performance in a bumblebee (Bombus terrestris) supports an evolutionary link between endocrine signaling and social complexity. Horm Behav 2016; 85:67-75. [PMID: 27503109 DOI: 10.1016/j.yhbeh.2016.08.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 08/03/2016] [Accepted: 08/04/2016] [Indexed: 01/21/2023]
Abstract
A hallmark of insect societies is a division of labor among workers specializing in different tasks. In bumblebees the division of labor is related to body size; relatively small workers are more likely to stay inside the nest and tend ("nurse") brood, whereas their larger sisters are more likely to forage. Despite their ecological and economic importance, very little is known about the endocrine regulation of division of labor in bumblebees. We studied the influence of juvenile hormone (JH) on task performance in the bumblebee Bombus terrestris. We first used a radioimmunoassay to measure circulating JH titers in workers specializing in nursing and foraging activities. Next, we developed new protocols for manipulating JH titers by combining a size-adjusted topical treatment with the allatotoxin Precocene-I and replacement therapy with JH-III. Finally, we used this protocol to test the influence of JH on task performance. JH levels were either similar for nurses and foragers (three colonies), or higher in nurses (two colonies). Nurses had better developed ovaries and JH levels were typically positively correlated with ovarian state. Manipulation of JH titers influenced ovarian development and wax secretion, consistent with earlier allatectomy studies. These manipulations however, did not affect nursing or foraging activity, or the likelihood to specialize in nursing or foraging activity. These findings contrast with honeybees in which JH influences age-related division of labor but not adult female fertility. Thus, the evolution of complex societies in bees was associated with modifications in the way JH influences social behavior.
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Affiliation(s)
- Hagai Y Shpigler
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Adam J Siegel
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Zachary Y Huang
- Department of Entomology, Michigan State University, East Lansing, MI, USA
| | - Guy Bloch
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
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27
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Complex patterns of differential expression in candidate master regulatory genes for social behavior in honey bees. Behav Ecol Sociobiol 2016. [DOI: 10.1007/s00265-016-2071-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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28
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Amsalem E, Galbraith DA, Cnaani J, Teal PEA, Grozinger CM. Conservation and modification of genetic and physiological toolkits underpinning diapause in bumble bee queens. Mol Ecol 2015; 24:5596-615. [PMID: 26453894 DOI: 10.1111/mec.13410] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Revised: 10/02/2015] [Accepted: 10/06/2015] [Indexed: 02/02/2023]
Abstract
Diapause is the key adaptation allowing insects to survive unfavourable conditions and inhabit an array of environments. Physiological changes during diapause are largely conserved across species and are hypothesized to be regulated by a conserved suite of genes (a 'toolkit'). Furthermore, it is hypothesized that in social insects, this toolkit was co-opted to mediate caste differentiation between long-lived, reproductive, diapause-capable queens and short-lived, sterile workers. Using Bombus terrestris queens, we examined the physiological and transcriptomic changes associated with diapause and CO2 treatment, which causes queens to bypass diapause. We performed comparative analyses with genes previously identified to be associated with diapause in the Dipteran Sarcophaga crassipalpis and with caste differentiation in bumble bees. As in Diptera, diapause in bumble bees is associated with physiological and transcriptional changes related to nutrient storage, stress resistance and core metabolic pathways. There is a significant overlap, both at the level of transcript and gene ontology, between the genetic mechanisms mediating diapause in B. terrestris and S. crassipalpis, reaffirming the existence of a conserved insect diapause genetic toolkit. However, a substantial proportion (10%) of the differentially regulated transcripts in diapausing queens have no clear orthologs in other species, and key players regulating diapause in Diptera (juvenile hormone and vitellogenin) appear to have distinct functions in bumble bees. We also found a substantial overlap between genes related to caste determination and diapause in bumble bees. Thus, our studies demonstrate an intriguing interplay between pathways underpinning adaptation to environmental extremes and the evolution of sociality in insects.
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Affiliation(s)
- Etya Amsalem
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
| | - David A Galbraith
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
| | | | - Peter E A Teal
- Chemistry Research Unit, US Department of Agriculture, 1600-1700 SW, 23rd Drive, Gainesville, FL, 32608, USA
| | - Christina M Grozinger
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
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29
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Woodard SH, Lozier JD, Goulson D, Williams PH, Strange JP, Jha S. Molecular tools and bumble bees: revealing hidden details of ecology and evolution in a model system. Mol Ecol 2015; 24:2916-36. [PMID: 25865395 DOI: 10.1111/mec.13198] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 04/07/2015] [Accepted: 04/08/2015] [Indexed: 01/15/2023]
Abstract
Bumble bees are a longstanding model system for studies on behaviour, ecology and evolution, due to their well-studied social lifestyle, invaluable role as wild and managed pollinators, and ubiquity and diversity across temperate ecosystems. Yet despite their importance, many aspects of bumble bee biology have remained enigmatic until the rise of the genetic and, more recently, genomic eras. Here, we review and synthesize new insights into the ecology, evolution and behaviour of bumble bees that have been gained using modern genetic and genomic techniques. Special emphasis is placed on four areas of bumble bee biology: the evolution of eusociality in this group, population-level processes, large-scale evolutionary relationships and patterns, and immunity and resistance to pesticides. We close with a prospective on the future of bumble bee genomics research, as this rapidly advancing field has the potential to further revolutionize our understanding of bumble bees, particularly in regard to adaptation and resilience. Worldwide, many bumble bee populations are in decline. As such, throughout the review, connections are drawn between new molecular insights into bumble bees and our understanding of the causal factors involved in their decline. Ongoing and potential applications to bumble bee management and conservation are also included to demonstrate how genetics- and genomics-enabled research aids in the preservation of this threatened group.
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Affiliation(s)
- S Hollis Woodard
- Department of Integrative Biology, University of Texas, Austin, TX, 78712, USA.,Department of Entomology, University of California, Riverside, CA, 92521, USA
| | - Jeffrey D Lozier
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, 35401, USA
| | - David Goulson
- Evolution, Behaviour & Environment, School of Life Sciences, University of Sussex, Falmer, East Sussex, BN1 9QG, UK
| | - Paul H Williams
- Department of Life Sciences, Natural History Museum, London, SW7 5BD, UK
| | - James P Strange
- USDA-ARS, Pollinating Insect Research Unit, Utah State University, Logan, UT, 84322, USA
| | - Shalene Jha
- Department of Integrative Biology, University of Texas, Austin, TX, 78712, USA
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30
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Marchal E, Hult EF, Huang J, Pang Z, Stay B, Tobe SS. Methoprene-tolerant (Met) knockdown in the adult female cockroach, Diploptera punctata completely inhibits ovarian development. PLoS One 2014; 9:e106737. [PMID: 25197795 PMCID: PMC4157775 DOI: 10.1371/journal.pone.0106737] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 07/08/2014] [Indexed: 02/06/2023] Open
Abstract
Independent of the design of the life cycle of any insect, their growth and reproduction are highly choreographed through the action of two versatile hormones: ecdysteroids and juvenile hormones (JH). However, the means by which JH can target tissues and exert its pleiotropic physiological effects is currently still not completely elucidated. Although the identity of the one JH receptor is currently still elusive, recent evidence seems to point to the product of the Methoprene-tolerant gene (Met) as the most likely contender in transducing the action of JH. Studies on the role of this transcription factor have mostly been focused on immature insect stages. In this study we used the viviparous cockroach Diploptera punctata, a favorite model in studying JH endocrinology, to examine the role of Met during reproduction. A tissue distribution and developmental profile of transcript levels was determined for Met and its downstream partners during the first gonadotropic cycle of this cockroach. Using RNA interference, our study shows that silencing Met results in an arrest of basal oocyte development; vitellogenin is no longer transcribed in the fat body and no longer taken up by the ovary. Patency is not induced in these animals which fail to produce the characteristic profile of JH biosynthesis typical of the first gonadotropic cycle. Moreover, the ultrastructure of the follicle cells showed conspicuous whorls of rough endoplasmic reticulum and a failure to form chorion. Our study describes the role of Met on a cellular and physiological level during insect reproduction, and confirms the role of Met as a key factor in the JH signaling pathway.
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Affiliation(s)
- Elisabeth Marchal
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | - Ekaterina F. Hult
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | - Juan Huang
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | - Zhenguo Pang
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| | - Barbara Stay
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Stephen S. Tobe
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
- * E-mail:
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31
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Amsalem E, Teal P, Grozinger CM, Hefetz A. Precocene-I inhibits juvenile hormone biosynthesis, ovarian activation, aggression and alters sterility signal production in bumble bee (Bombus terrestris) workers. ACTA ACUST UNITED AC 2014; 217:3178-85. [PMID: 25013106 DOI: 10.1242/jeb.107250] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Juvenile hormone (JH) is an important regulator of development and physiology in insects. While in many insect species, including bumble bees, JH functions as gonadotropin in adults, in some highly eusocial insects its role has shifted to regulate social behavior including division of labor, dominance and aggression. Studying JH functions across social insect species is important for understanding the evolution of sociality; however, these studies have been limited because of the inability to reduce JH levels without surgically removing its glandular source, the corpora allata. Precocene is known to inhibit JH biosynthesis in several non-social insects, but has been poorly studied in social insects. Here, we tested whether precocene-I can effectively reduce JH levels in Bombus terrestris workers, and examined its effects on their physiology and behavior. Precocene-I treatment of three-worker groups decreased JH titer and ovarian activation, irrespective of the bees' dominance rank within the group, and was remedied by JH replacement therapy. Precocene-I also decreased aggressiveness and increased ester-sterility signal production; these changes were rank-dependent, and affected mainly the most reproductive and the least aggressive workers, respectively, and could not be remedied by JH replacement therapy. These results clearly confirm the role of JH as a gonadotropin and mediator of aggression in B. terrestris, and indicate that JH effects are associated with worker dominance rank. The ability to chemically reduce JH titer provides us with a non-intrusive method to probe the evolutionary changes associated with JH and the hormonal mechanisms that are associated with reproduction and behavior in social insects.
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Affiliation(s)
- E Amsalem
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, The Pennsylvania State University, University Park, PA 16802, USA
| | - P Teal
- Chemistry Research Unit, 1600-1700 SW, 23rd Drive, Gainesville, FL 32608, USA
| | - C M Grozinger
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, The Pennsylvania State University, University Park, PA 16802, USA
| | - A Hefetz
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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32
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Shpigler H, Amsalem E, Huang ZY, Cohen M, Siegel AJ, Hefetz A, Bloch G. Gonadotropic and physiological functions of juvenile hormone in Bumblebee (Bombus terrestris) workers. PLoS One 2014; 9:e100650. [PMID: 24959888 PMCID: PMC4069101 DOI: 10.1371/journal.pone.0100650] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 05/29/2014] [Indexed: 11/21/2022] Open
Abstract
The evolution of advanced sociality in bees is associated with apparent modifications in juvenile hormone (JH) signaling. By contrast to most insects in which JH is a gonadotropin regulating female fertility, in the highly eusocial honey bee (Apis mellifera) JH has lost its gonadotrophic function in adult females, and instead regulates age-related division of labor among worker bees. In order to shed light on the evolution of JH signaling in bees we performed allatectomy and replacement therapies to manipulate JH levels in workers of the "primitively eusocial" bumblebee Bombus terrestris. Allatectomized worker bees showed remarkable reduction in ovarian development, egg laying, Vitellogenin and Krüppel homolog 1 fat body transcript levels, hemolymph Vitellogenin protein abundance, wax secretion, and egg-cell construction. These effects were reverted, at least partially, by treating allatectomized bees with JH-III, the natural JH of bees. Allatectomy also affected the amount of ester component in Dufour's gland secretion, which is thought to convey a social signal relating to worker fertility. These findings provide a strong support for the hypothesis that in contrast to honey bees, JH is a gonadotropin in bumblebees and lend credence to the hypothesis that the evolution of advanced eusociality in honey bees was associated with major modifications in JH signaling.
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Affiliation(s)
- Hagai Shpigler
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
- * E-mail:
| | - Etya Amsalem
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Zachary Y. Huang
- Department of Entomology, Michigan State University, East Lansing, Michigan, United States of America
| | - Mira Cohen
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Adam J. Siegel
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Abraham Hefetz
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Guy Bloch
- Department of Ecology, Evolution, and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
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33
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Amsalem E, Malka O, Grozinger C, Hefetz A. Exploring the role of juvenile hormone and vitellogenin in reproduction and social behavior in bumble bees. BMC Evol Biol 2014; 14:45. [PMID: 24618396 PMCID: PMC4007805 DOI: 10.1186/1471-2148-14-45] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 02/21/2014] [Indexed: 12/12/2022] Open
Abstract
Background The genetic and physiological pathways regulating behavior in solitary species are hypothesized to have been co-opted to regulate social behavior in social species. One classic example is the interaction between vitellogenin (an egg-yolk and storage protein) and juvenile hormone, which are positively correlated in most insect species but have modified interactions in highly eusocial insects. In some of these species (including some termites, ants, and the honey bee), juvenile hormone and vitellogenin levels are negatively correlated and juvenile hormone has shifted its role from a gonadotropin to a regulator of maturation and division of labor in the primarily sterile workers. The function of vitellogenin also seems to have broadened to encompass similar roles. Thus, the functions and molecular interactions of juvenile hormone and vitellogenin are hypothesized to have undergone changes during the evolution of eusociality, but the mechanisms underlying these changes are unknown. Bumble bees offer an excellent model system for testing how the relationship between juvenile hormone and vitellogenin evolved from solitary to social species. Bumble bee colonies are primitively eusocial and comprised of a single reproductive queen and facultatively sterile workers. In Bombus terrestris, juvenile hormone retains its ancestral role as a gonadotropin and is also hypothesized to regulate aggressive behavior. However, the function of vitellogenin and its interactions with juvenile hormone have not yet been characterized. Results By characterizing vitellogenin RNA expression levels (vg) in B. terrestris we show that vg is not associated with task and only partially associated with worker age, queen presence, and caste (queen vs worker). The correlations of vg with ovarian activation were not consistent across experiments, but both vg and ovarian activation were significantly associated with levels of aggression experienced by workers. Treatment with juvenile hormone did not affect vg levels in queenless groups. Conclusions We suggest that social interactions affect vg levels more strongly than a worker’s reproductive physiological state, and that juvenile hormone and vg are uncoupled in this species. Thus, although juvenile hormone maintains its traditional role as gonadotropin in B. terrestris, vg has already been co-opted into a novel role, consistent with the model that Bombus represents an intermediate stage in the evolution of eusociality.
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Affiliation(s)
- Etya Amsalem
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, The Pennsylvania State University, University Park, PA 16802, USA.
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34
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Woodard SH, Bloch GM, Band MR, Robinson GE. Molecular heterochrony and the evolution of sociality in bumblebees (Bombus terrestris). Proc Biol Sci 2014; 281:20132419. [PMID: 24552837 DOI: 10.1098/rspb.2013.2419] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Sibling care is a hallmark of social insects, but its evolution remains challenging to explain at the molecular level. The hypothesis that sibling care evolved from ancestral maternal care in primitively eusocial insects has been elaborated to involve heterochronic changes in gene expression. This elaboration leads to the prediction that workers in these species will show patterns of gene expression more similar to foundress queens, who express maternal care behaviour, than to established queens engaged solely in reproductive behaviour. We tested this idea in bumblebees (Bombus terrestris) using a microarray platform with approximately 4500 genes. Unlike the wasp Polistes metricus, in which support for the above prediction has been obtained, we found that patterns of brain gene expression in foundress and queen bumblebees were more similar to each other than to workers. Comparisons of differentially expressed genes derived from this study and gene lists from microarray studies in Polistes and the honeybee Apis mellifera yielded a shared set of genes involved in the regulation of related social behaviours across independent eusocial lineages. Together, these results suggest that multiple independent evolutions of eusociality in the insects might have involved different evolutionary routes, but nevertheless involved some similarities at the molecular level.
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Affiliation(s)
- S Hollis Woodard
- Department of Integrative Biology, University of Texas at Austin, , Austin, TX 78712, USA, Department of Ecology, Evolution and Behavior, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, , Jerusalem 91904, Israel, W. M. Keck Center for Comparative and Functional Genomics, University of Illinois, , Urbana, IL 61801, USA, Department of Entomology, University of Illinois, , Urbana, IL 61801, USA, Institute for Genomic Biology, University of Illinois, , Urbana, IL 61801, USA, Neuroscience Program, University of Illinois, , Urbana, IL 61801, USA
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35
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Atallah J, Plachetzki DC, Jasper WC, Johnson BR. The utility of shallow RNA-Seq for documenting differential gene expression in genes with high and low levels of expression. PLoS One 2013; 8:e84160. [PMID: 24358338 PMCID: PMC3865247 DOI: 10.1371/journal.pone.0084160] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 11/20/2013] [Indexed: 11/18/2022] Open
Abstract
The sequencing depth necessary for documenting differential gene expression using RNA-Seq has been little explored outside of model systems. In particular, the depth required to analyze large-scale patterns of differential transcription factor expression is not known. The goal of the present study is to explore the effectiveness of shallow (relatively low read depth) RNA-Seq. We focus on two tissues in the honey bee: the sting gland and the digestive tract. The sting gland is an experimentally well-understood tissue that we use to benchmark the utility of this approach. We use the digestive tract to test the results obtained with the sting gland, and to conduct RNA-Seq between tissue types. Using a list of experimentally verified genes conferring tissue-specific functions in the sting gland, we show that relatively little read depth is necessary to identify them. We argue that this result should be broadly applicable, since genes important for tissue-specific functions often have robust expression patterns, and because we obtained similar results in our analysis of the digestive tract. Furthermore, we demonstrate that the differential expression of transcription factors, which are transcribed at low levels compared to other genes, can nevertheless often be determined using shallow RNA-Seq. Overall, we find over 150 differentially expressed transcription factors in our tissues at a read depth of only 12 million. This work shows the utility of low-depth sequencing for identifying genes important for tissue-specific functions. It also verifies the often-held belief that transcription factors show low levels of expression, while demonstrating that, in spite of this, they are frequently amenable to shallow RNA-Seq. Our findings should be of benefit to researchers using RNA-Seq in many different biological systems.
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Affiliation(s)
- Joel Atallah
- Department of Entomology, University of California Davis, Davis, California, United States of America
| | - David C. Plachetzki
- Department of Ecology and Evolution, University of California Davis, Davis, California, United States of America
| | - W. Cameron Jasper
- Department of Entomology, University of California Davis, Davis, California, United States of America
| | - Brian R. Johnson
- Department of Entomology, University of California Davis, Davis, California, United States of America
- * E-mail:
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Transcriptional regulation of tissue organization and cell morphogenesis: the fly retina as a case study. Dev Biol 2013; 385:168-78. [PMID: 24099926 DOI: 10.1016/j.ydbio.2013.09.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 09/27/2013] [Accepted: 09/29/2013] [Indexed: 12/11/2022]
Abstract
Understanding how a functional organ can be produced from a small group of cells remains an outstanding question in cell and developmental biology. The developing compound eye of Drosophila has long been a model of choice for addressing this question by dissecting the cellular, genetic and molecular pathways that govern cell specification, differentiation, and multicellular patterning during organogenesis. In this review, the author focussed on cell and tissue morphogenesis during fly retinal development, including the regulated changes in cell shape and cell packing that ultimately determine the shape and architecture of the compound eye. In particular, the author reviewed recent studies that highlight the prominent roles of transcriptional and hormonal controls that orchestrate the cell shape changes, cell-cell junction remodeling and polarized membrane growth that underlie photoreceptor morphogenesis and retinal patterning.
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37
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Establishment of a versatile cell line for juvenile hormone signaling analysis in Tribolium castaneum. Sci Rep 2013; 3:1570. [PMID: 23535851 PMCID: PMC3610134 DOI: 10.1038/srep01570] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 03/13/2013] [Indexed: 11/09/2022] Open
Abstract
The red flour beetle, Tribolium castaneum, has been widely used as a laboratory model for analyzing gene function. In this study, we established a novel cell line (Tc81) from T. castaneum embryos and validated the utility of this cell line by analyzing the juvenile hormone (JH) signaling pathway. In Tc81 cells, the Krüppel homolog 1 gene (Kr-h1), which is a JH-dependent repressor of insect metamorphosis, was rapidly induced by subnanomolar levels of JHs. Bioinformatics analysis and reporter assays identified 2 JH response elements (kJHREs) located in the region upstream of the transcription start site and in the first intron of Kr-h1. Furthermore, methoprene tolerant (Met) and steroid receptor co-activator (SRC) RNAi reduced JH-dependent induction of Kr-h1 transcripts and kJHRE-reporter activities. Thus, this novel Tc81 cell line is useful for the elucidation of JH signaling and is a promising tool for the functional analysis of genes by RNAi and reporter assays.
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Sasaki K, Akasaka S, Mezawa R, Shimada K, Maekawa K. Regulation of the brain dopaminergic system by juvenile hormone in honey bee males (Apis mellifera L.). INSECT MOLECULAR BIOLOGY 2012; 21:502-509. [PMID: 22805503 DOI: 10.1111/j.1365-2583.2012.01153.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Dopamine (DA) and juvenile hormone (JH) are multifunctional regulators of behaviour in social insects, with distinct effects across species and even between different dominance positions within the same species. We examined the effects of JH on the brain dopaminergic system in honey bee males to investigate the potential relationship between JH and DA within Apis mellifera. Both DA content and the expression of three DA receptor genes (Amdop1, Amdop2 and Amdop3) increased in the male honey bee brain from day 4 to day 8 after emergence. Treatment of 4-day-old males with a JH analogue (methoprene, JHA) enhanced brain DA levels. Brain expression of Amdop1 was also enhanced by JHA but not by a DA receptor agonist 2-amino 6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN), indicating that Amdop1 up-regulation was not mediated by increased DA receptor stimulation. Furthermore, Amdop1 expression was still enhanced when JHA was co-applied with the DA receptor antagonist cis-(Z)-flupenthixol. Expression levels of Amdop2 and Amdop3 were not altered by JHA, 6,7-ADTN or by JHA plus the DA receptor antagonist. Regulation of the brain dopaminergic system by JH, as observed in solitary species, is conserved in male honey bees but not in female honey bees and other advanced eusocial insects.
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Affiliation(s)
- K Sasaki
- Graduate Program in Bioscience and Chemistry, Human Information Systems, Kanazawa Institute of Technology, Ishikawa, Japan.
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Greenberg JK, Xia J, Zhou X, Thatcher SR, Gu X, Ament SA, Newman TC, Green PJ, Zhang W, Robinson GE, Ben-Shahar Y. Behavioral plasticity in honey bees is associated with differences in brain microRNA transcriptome. GENES BRAIN AND BEHAVIOR 2012; 11:660-70. [PMID: 22409512 DOI: 10.1111/j.1601-183x.2012.00782.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Small, non-coding microRNAs (miRNAs) have been implicated in many biological processes, including the development of the nervous system. However, the roles of miRNAs in natural behavioral and neuronal plasticity are not well understood. To help address this we characterized the microRNA transcriptome in the adult worker honey bee head and investigated whether changes in microRNA expression levels in the brain are associated with division of labor among honey bees, a well-established model for socially regulated behavior. We determined that several miRNAs were downregulated in bees that specialize on brood care (nurses) relative to foragers. Additional experiments showed that this downregulation is dependent upon social context; it only occurred when nurse bees were in colonies that also contained foragers. Analyses of conservation patterns of brain-expressed miRNAs across Hymenoptera suggest a role for certain miRNAs in the evolution of the Aculeata, which includes all the eusocial hymenopteran species. Our results support the intriguing hypothesis that miRNAs are important regulators of social behavior at both developmental and evolutionary time scales.
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Affiliation(s)
- J K Greenberg
- Department of Biology, Washington University, St. Louis, MO, USA
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Lozano J, Belles X. Conserved repressive function of Krüppel homolog 1 on insect metamorphosis in hemimetabolous and holometabolous species. Sci Rep 2011; 1:163. [PMID: 22355678 PMCID: PMC3240953 DOI: 10.1038/srep00163] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 11/08/2011] [Indexed: 11/26/2022] Open
Abstract
Insect metamorphosis is regulated by ecdysteroids, which induce molts, and juvenile hormone
(JH), which inhibits metamorphic changes. The molecular action of ecdysteroids has been
thoroughly studied, but that of JH is poorly understood, with data currently only being
available for holometabolous species, like Drosophila melanogaster and Tribolium
castaneum. We studied the function of Krüppel homolog 1 (Kr-h1) in Blattella
germanica, a hemimetabolous model. Kr-h1 is a Zn finger transcription factor whose
function as transductor of the antimetamorphic action of JH has recently been demonstrated
in D. melanogaster and T. castaneum. The RNAi experiments reported herein
indicated that Kr-h1 transduces the antimetamorphic action of JH also in B.
germanica, thereby suggesting that this role is an ancestral condition that has been
conserved in insect evolution from hemimetabolous to holometabolous species.
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Affiliation(s)
- Jesus Lozano
- Institut de Biologia Evolutiva (CSIC-UPF), Passeig Martim de la Barceloneta 37 , 08003 Barcelona, Spain
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Bloch G, Grozinger CM. Social molecular pathways and the evolution of bee societies. Philos Trans R Soc Lond B Biol Sci 2011; 366:2155-70. [PMID: 21690132 PMCID: PMC3130366 DOI: 10.1098/rstb.2010.0346] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Bees provide an excellent model with which to study the neuronal and molecular modifications associated with the evolution of sociality because relatively closely related species differ profoundly in social behaviour, from solitary to highly social. The recent development of powerful genomic tools and resources has set the stage for studying the social behaviour of bees in molecular terms. We review 'ground plan' and 'genetic toolkit' models which hypothesize that discrete pathways or sets of genes that regulate fundamental behavioural and physiological processes in solitary species have been co-opted to regulate complex social behaviours in social species. We further develop these models and propose that these conserved pathways and genes may be incorporated into 'social pathways', which consist of relatively independent modules involved in social signal detection, integration and processing within the nervous and endocrine systems, and subsequent behavioural outputs. Modifications within modules or in their connections result in the evolution of novel behavioural patterns. We describe how the evolution of pheromonal regulation of social pathways may lead to the expression of behaviour under new social contexts, and review plasticity in circadian rhythms as an example for a social pathway with a modular structure.
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Affiliation(s)
- Guy Bloch
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.
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Graham AM, Munday MD, Kaftanoglu O, Page RE, Amdam GV, Rueppell O. Support for the reproductive ground plan hypothesis of social evolution and major QTL for ovary traits of Africanized worker honey bees (Apis mellifera L.). BMC Evol Biol 2011; 11:95. [PMID: 21489230 PMCID: PMC3100260 DOI: 10.1186/1471-2148-11-95] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 04/13/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The reproductive ground plan hypothesis of social evolution suggests that reproductive controls of a solitary ancestor have been co-opted during social evolution, facilitating the division of labor among social insect workers. Despite substantial empirical support, the generality of this hypothesis is not universally accepted. Thus, we investigated the prediction of particular genes with pleiotropic effects on ovarian traits and social behavior in worker honey bees as a stringent test of the reproductive ground plan hypothesis. We complemented these tests with a comprehensive genome scan for additional quantitative trait loci (QTL) to gain a better understanding of the genetic architecture of the ovary size of honey bee workers, a morphological trait that is significant for understanding social insect caste evolution and general insect biology. RESULTS Back-crossing hybrid European x Africanized honey bee queens to the Africanized parent colony generated two study populations with extraordinarily large worker ovaries. Despite the transgressive ovary phenotypes, several previously mapped QTL for social foraging behavior demonstrated ovary size effects, confirming the prediction of pleiotropic genetic effects on reproductive traits and social behavior. One major QTL for ovary size was detected in each backcross, along with several smaller effects and two QTL for ovary asymmetry. One of the main ovary size QTL coincided with a major QTL for ovary activation, explaining 3/4 of the phenotypic variance, although no simple positive correlation between ovary size and activation was observed. CONCLUSIONS Our results provide strong support for the reproductive ground plan hypothesis of evolution in study populations that are independent of the genetic stocks that originally led to the formulation of this hypothesis. As predicted, worker ovary size is genetically linked to multiple correlated traits of the complex division of labor in worker honey bees, known as the pollen hoarding syndrome. The genetic architecture of worker ovary size presumably consists of a combination of trait-specific loci and general regulators that affect the whole behavioral syndrome and may even play a role in caste determination. Several promising candidate genes in the QTL intervals await further study to clarify their potential role in social insect evolution and the regulation of insect fertility in general.
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Affiliation(s)
- Allie M Graham
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27403, USA
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