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Fandino RA, Brady NK, Chatterjee M, McDonald JMC, Livraghi L, van der Burg KRL, Mazo-Vargas A, Markenscoff-Papadimitriou E, Reed RD. The ivory lncRNA regulates seasonal color patterns in buckeye butterflies. Proc Natl Acad Sci U S A 2024; 121:e2403426121. [PMID: 39352931 DOI: 10.1073/pnas.2403426121] [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: 02/18/2024] [Accepted: 08/19/2024] [Indexed: 10/04/2024] Open
Abstract
Long noncoding RNAs (lncRNAs) are transcribed elements increasingly recognized for their roles in regulating gene expression. Thus far, however, we have little understanding of how lncRNAs contribute to evolution and adaptation. Here, we show that a conserved lncRNA, ivory, is an important color patterning gene in the buckeye butterfly Junonia coenia. ivory overlaps with cortex, a locus linked to multiple cases of crypsis and mimicry in Lepidoptera. Along with a companion paper by Livraghi et al., we argue that ivory, not cortex, is the color pattern gene of interest at this locus. In J. coenia, a cluster of cis-regulatory elements (CREs) in the first intron of ivory are genetically associated with natural variation in seasonal color pattern plasticity, and targeted deletions of these CREs phenocopy seasonal phenotypes. Deletions of different ivory CREs produce other distinct phenotypes as well, including loss of melanic eyespot rings, and positive and negative changes in overall wing pigmentation. We show that the color pattern transcription factors Spineless, Bric-a-brac, and Ftz-f1 bind to the ivory promoter during wing pattern development, suggesting that they directly regulate ivory. This case study demonstrates how cis-regulation of a single noncoding RNA can exert diverse and nuanced effects on the evolution and development of color patterns, including modulating seasonally plastic color patterns.
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Affiliation(s)
- Richard A Fandino
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
| | - Noah K Brady
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
| | - Martik Chatterjee
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
| | - Jeanne M C McDonald
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
| | - Luca Livraghi
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
| | - Karin R L van der Burg
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
- Department of Biological Sciences, Clemson University, Clemson, SC 29631
| | - Anyi Mazo-Vargas
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
| | | | - Robert D Reed
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
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Livraghi L, Hanly JJ, Evans E, Wright CJ, Loh LS, Mazo-Vargas A, Kamrava K, Carter A, van der Heijden ESM, Reed RD, Papa R, Jiggins CD, Martin A. A long noncoding RNA at the cortex locus controls adaptive coloration in butterflies. Proc Natl Acad Sci U S A 2024; 121:e2403326121. [PMID: 39213180 PMCID: PMC11388343 DOI: 10.1073/pnas.2403326121] [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: 02/16/2024] [Accepted: 07/22/2024] [Indexed: 09/04/2024] Open
Abstract
Evolutionary variation in the wing pigmentation of butterflies and moths offers striking examples of adaptation by crypsis and mimicry. The cortex locus has been independently mapped as the locus controlling color polymorphisms in 15 lepidopteran species, suggesting that it acts as a genomic hotspot for the diversification of wing patterns, but functional validation through protein-coding knockouts has proven difficult to obtain. Our study unveils the role of a long noncoding RNA (lncRNA) which we name ivory, transcribed from the cortex locus, in modulating color patterning in butterflies. Strikingly, ivory expression prefigures most melanic patterns during pupal development, suggesting an early developmental role in specifying scale identity. To test this, we generated CRISPR mosaic knock-outs in five nymphalid butterfly species and show that ivory mutagenesis yields transformations of dark pigmented scales into white or light-colored scales. Genotyping of Vanessa cardui germline mutants associates these phenotypes to small on-target deletions at the conserved first exon of ivory. In contrast, cortex germline mutant butterflies with confirmed null alleles lack any wing phenotype and exclude a color patterning role for this adjacent gene. Overall, these results show that a lncRNA gene acts as a master switch of color pattern specification and played key roles in the adaptive diversification of wing patterns in butterflies.
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Affiliation(s)
- Luca Livraghi
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom
| | - Joseph J Hanly
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
- Department of Biology, Duke University, Durham, NC 27708
- Smithsonian Tropical Research Institute, Gamboa, Panama
| | - Elizabeth Evans
- Department of Biology, University of Puerto Rico at Río Piedras, San Juan 00925, Puerto Rico
| | - Charlotte J Wright
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1RQ, United Kingdom
| | - Ling S Loh
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
| | - Anyi Mazo-Vargas
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
- Department of Biology, Duke University, Durham, NC 27708
| | - Kiana Kamrava
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
| | - Alexander Carter
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
| | - Eva S M van der Heijden
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1RQ, United Kingdom
| | - Robert D Reed
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853
| | - Riccardo Papa
- Department of Biology, University of Puerto Rico at Río Piedras, San Juan 00925, Puerto Rico
- Comprehensive Cancer Center, University of Puerto Rico, San Juan 00925, Puerto Rico
- Molecular Sciences and Research Center, University of Puerto Rico, San Juan 00926, Puerto Rico
- Dipartimento di Scienze Chimiche della Vita e della Sostenibilità Ambientale, Università di Parma, Parma 43124, Italy
| | - Chris D Jiggins
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom
| | - Arnaud Martin
- Department of Biological Sciences, The George Washington University, Washington, DC 20052
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Nakazato Y, Otaki JM. Socket Array Irregularities and Wing Membrane Distortions at the Eyespot Foci of Butterfly Wings Suggest Mechanical Signals for Color Pattern Determination. INSECTS 2024; 15:535. [PMID: 39057268 PMCID: PMC11276954 DOI: 10.3390/insects15070535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2024] [Revised: 07/09/2024] [Accepted: 07/14/2024] [Indexed: 07/28/2024]
Abstract
Eyespot foci on butterfly wings function as organizers of eyespot color patterns during development. Despite their importance, focal structures have not been examined in detail. Here, we microscopically examined scales, sockets, and the wing membrane in the butterfly eyespot foci of both expanded and unexpanded wings using the Blue Pansy butterfly Junonia orithya. Images from a high-resolution light microscope revealed that, although not always, eyespot foci had scales with disordered planar polarity. Scanning electron microscopy (SEM) images after scale removal revealed that the sockets were irregularly positioned and that the wing membrane was physically distorted as if the focal site were mechanically squeezed from the surroundings. Focal areas without eyespots also had socket array irregularities, but less frequently and less severely. Physical damage in the background area induced ectopic patterns with socket array irregularities and wing membrane distortions, similar to natural eyespot foci. These results suggest that either the process of determining an eyespot focus or the function of an eyespot organizer may be associated with wing-wide mechanics that physically disrupt socket cells, scale cells, and the wing membrane, supporting the physical distortion hypothesis of the induction model for color pattern determination in butterfly wings.
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Affiliation(s)
| | - Joji M. Otaki
- The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara 903-0213, Okinawa, Japan
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Tian S, Asano Y, Banerjee TD, Wee JLQ, Lamb A, Wang Y, Murugesan SN, Ui-Tei K, Wittkopp PJ, Monteiro A. A micro-RNA is the effector gene of a classic evolutionary hotspot locus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.09.579741. [PMID: 38659873 PMCID: PMC11042203 DOI: 10.1101/2024.02.09.579741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
In Lepidoptera (butterflies and moths), the genomic region around the gene cortex is a 'hotspot' locus, repeatedly used to generate intraspecific melanic wing color polymorphisms across 100-million-years of evolution. However, the identity of the effector gene regulating melanic wing color within this locus remains unknown. Here, we show that none of the four candidate protein-coding genes within this locus, including cortex, serve as major effectors. Instead, a micro-RNA (miRNA), mir-193, serves as the major effector across three deeply diverged lineages of butterflies, and its function is conserved in Drosophila. In Lepidoptera, mir-193 is derived from a gigantic long non-coding RNA, ivory, and it functions by directly repressing multiple pigmentation genes. We show that a miRNA can drive repeated instances of adaptive evolution in animals.
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Affiliation(s)
- Shen Tian
- Department of Biological Sciences, Faculty of Science, National University of Singapore; Singapore, 117543, Singapore
| | - Yoshimasa Asano
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo; Tokyo, 113-0033, Japan
| | - Tirtha Das Banerjee
- Department of Biological Sciences, Faculty of Science, National University of Singapore; Singapore, 117543, Singapore
| | - Jocelyn Liang Qi Wee
- Department of Biological Sciences, Faculty of Science, National University of Singapore; Singapore, 117543, Singapore
| | - Abigail Lamb
- Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, The University of Michigan; Ann Arbor, MI 48109-1085, USA
| | - Yehan Wang
- Department of Biological Sciences, Faculty of Science, National University of Singapore; Singapore, 117543, Singapore
| | - Suriya Narayanan Murugesan
- Department of Biological Sciences, Faculty of Science, National University of Singapore; Singapore, 117543, Singapore
| | - Kumiko Ui-Tei
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo; Tokyo, 113-0033, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo; Chiba, 277-8561, Japan
| | - Patricia J. Wittkopp
- Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, The University of Michigan; Ann Arbor, MI 48109-1085, USA
- Department of Ecology and Evolutionary Biology, College of Literature, Science, and the Arts, The University of Michigan; Ann Arbor, MI 48109-1085, USA
| | - Antónia Monteiro
- Department of Biological Sciences, Faculty of Science, National University of Singapore; Singapore, 117543, Singapore
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Tendolkar A, Mazo-Vargas A, Livraghi L, Hanly JJ, Van Horne KC, Gilbert LE, Martin A. Cis-regulatory modes of Ultrabithorax inactivation in butterfly forewings. eLife 2024; 12:RP90846. [PMID: 38261357 PMCID: PMC10945631 DOI: 10.7554/elife.90846] [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] [Indexed: 01/24/2024] Open
Abstract
Hox gene clusters encode transcription factors that drive regional specialization during animal development: for example the Hox factor Ubx is expressed in the insect metathoracic (T3) wing appendages and differentiates them from T2 mesothoracic identities. Hox transcriptional regulation requires silencing activities that prevent spurious activation and regulatory crosstalks in the wrong tissues, but this has seldom been studied in insects other than Drosophila, which shows a derived Hox dislocation into two genomic clusters that disjoined Antennapedia (Antp) and Ultrabithorax (Ubx). Here, we investigated how Ubx is restricted to the hindwing in butterflies, amidst a contiguous Hox cluster. By analysing Hi-C and ATAC-seq data in the butterfly Junonia coenia, we show that a Topologically Associated Domain (TAD) maintains a hindwing-enriched profile of chromatin opening around Ubx. This TAD is bordered by a Boundary Element (BE) that separates it from a region of joined wing activity around the Antp locus. CRISPR mutational perturbation of this BE releases ectopic Ubx expression in forewings, inducing homeotic clones with hindwing identities. Further mutational interrogation of two non-coding RNA encoding regions and one putative cis-regulatory module within the Ubx TAD cause rare homeotic transformations in both directions, indicating the presence of both activating and repressing chromatin features. We also describe a series of spontaneous forewing homeotic phenotypes obtained in Heliconius butterflies, and discuss their possible mutational basis. By leveraging the extensive wing specialization found in butterflies, our initial exploration of Ubx regulation demonstrates the existence of silencing and insulating sequences that prevent its spurious expression in forewings.
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Affiliation(s)
- Amruta Tendolkar
- Department of Biological Sciences, The George Washington UniversityWashington, DCUnited States
| | - Anyi Mazo-Vargas
- Department of Biological Sciences, The George Washington UniversityWashington, DCUnited States
| | - Luca Livraghi
- Department of Biological Sciences, The George Washington UniversityWashington, DCUnited States
| | - Joseph J Hanly
- Department of Biological Sciences, The George Washington UniversityWashington, DCUnited States
- Smithsonian Tropical Research InstitutePanama CityPanama
| | - Kelsey C Van Horne
- Department of Biological Sciences, The George Washington UniversityWashington, DCUnited States
| | - Lawrence E Gilbert
- Department of Integrative Biology, University of Texas – AustinAustinUnited States
| | - Arnaud Martin
- Department of Biological Sciences, The George Washington UniversityWashington, DCUnited States
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