| NSF Org: |
IOS Division Of Integrative Organismal Systems |
| Recipient: |
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| Initial Amendment Date: | June 18, 2018 |
| Latest Amendment Date: | August 3, 2020 |
| Award Number: | 1755373 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Kimberly Gallagher
IOS Division Of Integrative Organismal Systems BIO Directorate for Biological Sciences |
| Start Date: | July 15, 2018 |
| End Date: | June 30, 2023 (Estimated) |
| Total Intended Award Amount: | $588,044.00 |
| Total Awarded Amount to Date: | $588,044.00 |
| Funds Obligated to Date: |
FY 2020 = $179,578.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
438 WHITNEY RD EXTENSION UNIT 1133 STORRS CT US 06269-9018 (860)486-3622 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
75 N. Eagleville Road Uniy 3043 Storrs CT US 06269-3043 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | PLANT FUNGAL & MICROB DEV MECH |
| Primary Program Source: |
01002021DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.074 |
ABSTRACT
About one third of the ~300,000 flowering plant species (e.g., petunia, snapdragon, primrose, rhododendron) produce flowers with petals fused into a tubular structure referred to as the corolla tube. The corolla tube encloses and protects the nectaries and reproductive organs. Differences in the length, width, and curvature of the corolla tube have led to an endless variety of differently shaped flowers that attract specialized groups of pollinators (e.g., beeflies, hawkmoths, hummingbirds, nectar bats). Because of its importance in plant reproduction, the corolla tube is considered a key morphological innovation that contributes to plant diversification and speciation. This study employs a new genetic model system, monkeyflowers (Mimulus lewisii), to identify and characterize the genes responsible for corolla tube development, including the genes responsible for coordinated organ fusion and the generation of a diversity of corolla tube shape. The flower images, pollination videos, and interactive, multimedia illustrations resulting from this project will be incorporated into a new Plant Biology section on the nationally and internationally recognized Learn.Genetics website as online educational resources for K-16 students. Multi-disciplinary training in genetics, development, and evolution includes post-doctoral associates, graduate students and undergraduate students, including members of under-represented groups enrolled in the McNair Scholars Program at UConn.
This study leverages recently developed genomic resources, stable transgenic tools, and chemically induced mutants of monkeyflowers (Mimulus) to identify and characterize genes that control corolla tube formation. Results from preliminary work in the investigator's laboratory allows the formulation of a new conceptual model for the developmental genetic control of corolla tube formation. At the heart of the model is auxin signaling that mediates coordinated growth between the bases of the initially separate petal primordia and the inter-primordial regions. Upstream of this core module is the genetic regulatory network (GRN) controlling lateral expansion of the petal primordia, essentially the same GRN that controls leaf adaxial/abaxial polarity and lamina growth. Downstream of this core module lie the organ boundary genes that suppress localized tissue growth if not repressed by auxin signaling. Two specific aims will be pursued to test these hypotheses: (i) Determine the functional roles of the major regulators of leaf polarity in corolla tube formation using in situ hybridization, ectopic gene expression, and RNA interference in the model species Mimulus lewisii. (ii) Identify additional components of the GRN controlling corolla tube formation by bulk segregant analyses of several additional non-allelic mutants of M. lewisii with unfused corollas. Genetic interactions among the newly identified genes and the known leaf polarity regulators will be determined by generating double or higher order combinatorial mutants and transgenic lines. RNA-Seq analyses of selected regulatory mutants and transgenic lines of the leaf polarity regulators will be conducted to identify downstream genes.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The major goal of this project is to elucidate the developmental mechanisms underlying the process of congenital petal fusion that forms the corolla tube, a floral structure that is found in over 80,000 flowering plants and plays a critical role in plant-pollinator interactions and speciation. To this end, we employed a new plant genetic model system, Mimulus lewisii, a monkeyflower species bearing flowers with a conspicuous corolla tube. Through genetic analyses of M. lewisii mutants with split corolla tubes and a series of transgenic experiments, we identified several regulatory genes that are required for corolla tube formation. By detailed comparison of the ontogenesis between the mutants and wild type, we found that the key to corolla tube formation is the synchronized growth between the bases of the petal primordia and the inter-primordial regions during early stages of flower development. Using a fluorescent reporter (DR5:RFP) for the phytohormone auxin, we discovered that auxin signaling is continuous in the synchronized growth zone during the critical stage of corolla tube formation in the wild type, but is much weaker or completely disrupted in the corolla tube mutants. Taken together, these results enabled us to establish a regulatory pathway and a new conceptual model for the developmental genetic control of corolla tube formation. At the heart of this model is auxin-induced synchronized growth of the marginal meristematic cells at the base of the petal primordia and the inter-primordial cells. Upstream of this core module is the tasiRNA-ARF3/4 pathway that regulates auxin homeostasis in the synchronized growth zone; downstream is an organ boundary gene (MlNAC1) that suppresses localized tissue growth if not repressed by auxin signaling. We expect that the conceptual model and regulatory pathway (i.e., tasiRNA-ARF3/4-auxin-MlNAC1) revealed in this study will serve the foundation for all future research on corolla tube development and evolution.
Another important outcome from this project is the auxin response reporter lines and plasma membrane marker lines that were generated to track auxin response dynamics by confocal microscopy in early-stage floral buds, where cell boundaries are clearly marked by the plasma membrane reporter protein. These auxin response reporter lines and plasma membrane marker lines will be an invaluable, permanent genetic resource for studying not only corolla tube formation, but also the development of all other plant organs in Mimulus.
As part of the Broad Impact activities, we have developed Mimubase (http://mimubase.org/), a centralized resource and information port for the entire Mimulus research community. We have also worked with a professional science communicator to produce a video that highlights the power of Mimulus in investigating the developmental genetics of understudied plant traits such as corolla tubes. The video will be released on the highly subscribed YouTube channel, Science IRL (‘in real life’). Furthermore, this project has contributed to the training and professional development of one postdoctoral researcher, two graduate students and two undergraduate students. All trainees have learned a great deal of developmental genetics, confocal imaging, and bioinformatics through this project, and have proceeded with their desired career paths (i.e., faculty, bioinformatician/postdoc, and graduate student).
Last Modified: 12/08/2023
Modified by: Yaowu Yuan
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