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LaFountain AM, McMahon HE, Reid NM, Yuan YW. To stripe or not to stripe: the origin of a novel foliar pigmentation pattern in monkeyflowers (Mimulus). New Phytol 2023; 237:310-322. [PMID: 36101514 PMCID: PMC10601762 DOI: 10.1111/nph.18486] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 09/07/2022] [Indexed: 06/15/2023]
Abstract
The origin of phenotypic novelty is one of the most challenging problems in evolutionary biology. Although genetic regulatory network rewiring or co-option has been widely recognised as a major contributor, in most cases how such genetic rewiring/co-option happens is completely unknown. We have studied a novel foliar pigmentation pattern that evolved recently in the monkeyflower species Mimulus verbenaceus. Through genome-wide association tests using wild-collected samples, experimental crosses of laboratory inbred lines, gene expression analyses, and functional assays, we identified an anthocyanin-activating R2R3-MYB gene, STRIPY, as the causal gene triggering the emergence of the discrete, mediolateral anthocyanin stripe in the M. verbenaceus leaf. Chemical mutagenesis revealed the existence of upstream activators and repressors that form a 'hidden' prepattern along the leaf proximodistal axis, potentiating the unique expression pattern of STRIPY. Population genomics analyses did not reveal signatures of positive selection, indicating that nonadaptive processes may be responsible for the establishment of this novel trait in the wild. This study demonstrates that the origin of phenotypic novelty requires at least two separate phases, potentiation and actualisation. The foliar stripe pattern of M. verbenaceus provides an excellent platform to probe the molecular details of both processes in future studies.
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Affiliation(s)
- Amy M. LaFountain
- Department of Ecology and Evolutionary Biology, University of Connecticut, 75 North Eagleville Road, Storrs, CT, USA. 06269-3043
| | - Hayley E. McMahon
- Department of Ecology and Evolutionary Biology, University of Connecticut, 75 North Eagleville Road, Storrs, CT, USA. 06269-3043
| | - Noah M. Reid
- Institute for Systems Genomics, University of Connecticut, 67 North Eagleville Road, Storrs, CT, USA 06269-3197
| | - Yao-Wu Yuan
- Department of Ecology and Evolutionary Biology, University of Connecticut, 75 North Eagleville Road, Storrs, CT, USA. 06269-3043
- Institute for Systems Genomics, University of Connecticut, 67 North Eagleville Road, Storrs, CT, USA 06269-3197
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Ding B, Li J, Gurung V, Lin Q, Sun X, Yuan YW. The leaf polarity factors SGS3 and YABBYs regulate style elongation through auxin signaling in Mimulus lewisii. New Phytol 2021; 232:2191-2206. [PMID: 34449905 DOI: 10.1111/nph.17702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 08/18/2021] [Indexed: 06/13/2023]
Abstract
Style length is a major determinant of breeding strategies in flowering plants and can vary dramatically between and within species. However, little is known about the genetic and developmental control of style elongation. We characterized the role of two classes of leaf adaxial-abaxial polarity factors, SUPPRESSOR OF GENE SILENCING3 (SGS3) and the YABBY family transcription factors, in the regulation of style elongation in Mimulus lewisii. We also examined the spatiotemporal patterns of auxin response during style development. Loss of SGS3 function led to reduced style length via limiting cell division, and downregulation of YABBY genes by RNA interference resulted in shorter styles by decreasing both cell division and cell elongation. We discovered an auxin response minimum between the stigma and ovary during the early stages of pistil development that marks style differentiation. Subsequent redistribution of auxin response to this region was correlated with style elongation. Auxin response was substantially altered when both SGS3 and YABBY functions were disrupted. We suggest that auxin signaling plays a central role in style elongation and that the way in which auxin signaling controls the different cell division and elongation patterns underpinning natural style length variation is a major question for future research.
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Affiliation(s)
- Baoqing Ding
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Jingjian Li
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, 510642, China
| | - Vandana Gurung
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Qiaoshan Lin
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Xuemei Sun
- Qinghai Key Laboratory of Genetics and Physiology of Vegetables, Qinghai University, Xining, 810008, China
| | - Yao-Wu Yuan
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
- Institute for Systems Genomics, University of Connecticut, Storrs, CT, 06269, USA
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Yuan YW. Monkeyflowers (Mimulus): new model for plant developmental genetics and evo-devo. New Phytol 2019; 222:694-700. [PMID: 30471231 DOI: 10.1111/nph.15560] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/18/2018] [Indexed: 06/09/2023]
Abstract
Contents Summary 694 I. Introduction 694 II. The system 695 III. Regulation of carotenoid pigmentation 695 IV. Formation of periodic pigmentation patterns 696 V. Developmental genetics of corolla tube formation and elaboration 697 VI. Molecular basis of floral trait variation underlying pollinator shift 698 VII. Outlook 699 Acknowledgements 699 References 699 SUMMARY: Monkeyflowers (Mimulus) have long been recognized as a classic ecological and evolutionary model system. However, only recently has it been realized that this system also holds great promise for studying the developmental genetics and evo-devo of important plant traits that are not found in well-established model systems such as Arabidopsis. Here, I review recent progress in four different areas of plant research enabled by this new model, including transcriptional regulation of carotenoid biosynthesis, formation of periodic pigmentation patterns, developmental genetics of corolla tube formation and elaboration, and the molecular basis of floral trait divergence underlying pollinator shift. These examples suggest that Mimulus offers ample opportunities to make exciting discoveries in plant development and evolution.
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Affiliation(s)
- Yao-Wu Yuan
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
- Institute for Systems Genomics, University of Connecticut, Storrs, CT, 06269, USA
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Sagawa JM, Stanley LE, LaFountain AM, Frank HA, Liu C, Yuan YW. An R2R3-MYB transcription factor regulates carotenoid pigmentation in Mimulus lewisii flowers. New Phytol 2016; 209:1049-57. [PMID: 26377817 DOI: 10.1111/nph.13647] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 08/14/2015] [Indexed: 05/19/2023]
Abstract
Carotenoids are yellow, orange, and red pigments that contribute to the beautiful colors and nutritive value of many flowers and fruits. The structural genes in the highly conserved carotenoid biosynthetic pathway have been well characterized in multiple plant systems, but little is known about the transcription factors that control the expression of these structural genes. By analyzing a chemically induced mutant of Mimulus lewisii through bulk segregant analysis and transgenic experiments, we have identified an R2R3-MYB, Reduced Carotenoid Pigmentation 1 (RCP1), as the first transcription factor that positively regulates carotenoid biosynthesis during flower development. Loss-of-function mutations in RCP1 lead to down-regulation of all carotenoid biosynthetic genes and reduced carotenoid content in M. lewisii flowers, a phenotype recapitulated by RNA interference in the wild-type background. Overexpression of this gene in the rcp1 mutant background restores carotenoid production and, unexpectedly, results in simultaneous decrease of anthocyanin production in some transgenic lines by down-regulating the expression of an activator of anthocyanin biosynthesis. Identification of transcriptional regulators of carotenoid biosynthesis provides the 'toolbox' genes for understanding the molecular basis of flower color diversification in nature and for potential enhancement of carotenoid production in crop plants via genetic engineering.
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Affiliation(s)
- Janelle M Sagawa
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Lauren E Stanley
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Amy M LaFountain
- Department of Chemistry, University of Connecticut, Storrs, CT, 06269, USA
| | - Harry A Frank
- Department of Chemistry, University of Connecticut, Storrs, CT, 06269, USA
| | - Chang Liu
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Yao-Wu Yuan
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
- Institute for Systems Genomics, University of Connecticut, Storrs, CT, 06269, USA
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Yuan YW, Sagawa JM, Frost L, Vela JP, Bradshaw HD. Transcriptional control of floral anthocyanin pigmentation in monkeyflowers (Mimulus). New Phytol 2014; 204:1013-27. [PMID: 25103615 PMCID: PMC4221532 DOI: 10.1111/nph.12968] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 07/05/2014] [Indexed: 05/04/2023]
Abstract
A molecular description of the control of floral pigmentation in a multi-species group displaying various flower color patterns is of great interest for understanding the molecular bases of phenotypic diversification and pollinator-mediated speciation. Through transcriptome profiling, mutant analyses and transgenic experiments, we aim to establish a 'baseline' floral anthocyanin regulation model in Mimulus lewisii and to examine the different ways of tinkering with this model in generating the diversity of floral anthocyanin patterns in other Mimulus species. We find one WD40 and one bHLH gene controlling anthocyanin pigmentation in the entire corolla of M. lewisii and two R2R3-MYB genes, PELAN and NEGAN, controlling anthocyanin production in the petal lobe and nectar guide, respectively. The autoregulation of NEGAN might be a critical property to generate anthocyanin spots. Independent losses of PELAN expression (via different mechanisms) explain two natural yellow-flowered populations of M. cardinalis (typically red-flowered). The NEGAN ortholog is the only anthocyanin-activating MYB expressed in the M. guttatus flowers. The mutant lines and transgenic tools available for M. lewisii will enable gene-by-gene replacement experiments to dissect the genetic and developmental bases of more complex floral color patterns, and to test hypotheses on phenotypic evolution in general.
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Affiliation(s)
- Yao-Wu Yuan
- Department of Biology, University of Washington, Seattle, WA 98195, USA
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Janelle M. Sagawa
- Department of Biology, University of Washington, Seattle, WA 98195, USA
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Laura Frost
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - James P. Vela
- Department of Biology, University of Washington, Seattle, WA 98195, USA
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