Plants - unlike animals- cannot escape when they find themselves in an inhospitable environment. Instead, plants cope by changing themselves, their final form or by delaying/accelerating the transition through phases in their lifecycle. Key to these coping strategies are small proteins that can move from one part of the plant to another, called florigen and antiflorigen. Florigen promotes more rapid development and flower formation, while antiflorigen has the opposite effect. The two regulators oppose each other and together act like a rheostat. What trajectory plants will eventually follow depends on the relative abundance of florigen to antiflorigen, which in turn is controlled by temperature, daylength and other cues. How does the balance of florigen and antiflorigen change plant form or the rate of its developmental transitions? Addressing this question has been hampered by technical challenges, florigen and antiflorigen can modulate accumulation of other key regulators; but, do not bind DNA to change transcription. The principal investigators have overcome these challenges and can now dissect where in the plant these developmental choice decisions are made, the precise processes put in place by antiflorigen and how it opposes florigen. Insights gained from these studies will be of broad general interest both by advancing understanding of the activity of these important regulators and by impacting agriculture. Traits modulated by florigen and antiflorigen in different crop species include such key agronomical traits such as tuberization, bulb formation, tree bud set and bud burst, seed dormancy, photoperiod-dependent flowering and flower architecture.

This project will leverage state-of the-art genetic, genomic, biochemical and cell biological approaches to provide mechanistic insight into the transcriptional pathways regulated by antiflorigen (TFL1), its repressive activity and the site of competitive action with florigen (FT). Specifically, imaging and genetic studies will probe whether FT, like TFL1, accumulates in and controls fate of axillary meristems. Standard and cell type specific RNAseq combined with network analyses will identify the pathways and the key components in each directly repressed by TFL1/FD. Finally, dual affinity purification combined with mass spectrometry (conducted in laboratory course) will uncover proteins that interact with and shape activity of the TFL1 complex. The combined activities will provide novel mechanistic insight into the question how key regulators of plant form and function execute their roles. The broader impacts, besides training of undergraduate students, graduate students and postdocs in independent research, will include mentoring of female scientists and training of 40 undergraduate students in research in laboratory courses. Students in two authentic research lab courses will conduct dual affinity purification combined with mass spectrometry, interpret the results and conduct follow-up experiments of their design. Finally, a lecture on research conducted in this proposal will be given to high school students during a summer research academy at Penn. Graduate students involved in the project will lead summer research academy lab sections, workshops and boot camps.

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.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
Standard Grant (Standard)
Application #
Program Officer
Anne W. Sylvester
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Pennsylvania
United States
Zip Code