Collaborative Research: EDGE CMT: Genomic and molecular bases of pollination syndrome evolution in monkeyflowers

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Variation of complex traits (e.g., human height) are usually caused by multiple genes. Identification and characterization of the causal genes and mutations underlying these polygenic traits remain a central challenge in biology. One of the most intriguing examples of polygenic adaptations in plants is the pollination syndrome, a suite of floral traits that enable specialized associations between flowers and their animal pollinators (e.g., bees, hummingbirds, hawkmoths). For example, hummingbird-pollinated flowers are usually large in size, red in color, with copious nectar production and exerted reproductive organs, whereas bee-pollinated flowers usually display various colors (but not red), a smaller quantity of nectar, inserted reproductive organs, and a clear landing platform. Evolutionary transitions from one pollination syndrome to another require coordinated changes of multiple floral traits, with each trait controlled by multiple genes, yet these switches occur rapidly in nature in many plant groups. This study employs a new genetic model system, monkeyflowers, to investigate how pollination syndrome switches occur at the genomic and molecular level. Furthermore, this study integrates research with student education and public outreach through the lens of pollination syndromes. Specific activities include organized pollinator observation experiments in a common garden on the University of Connecticut campus to raise public awareness of animal pollination service, creation of a bioinformatic Course-based Undergraduate Research Experience at Haverford College, and production of professional videos that bring pollination syndrome research to life and that will be released on a highly subscribed YouTube channel, Science IRL (‘in real life’).The overall objective of this project is to systematically dissect the genomic and molecular bases of floral trait variation among three closely related monkeyflower (Mimulus) species that display three distinct pollination syndromes, including the bee-pollinated M. lewisii, the hummingbird-pollinated M. cardinalis, and the self-pollinated M. parishii. These species are amenable to fine-scale genetic mapping and rigorous functional interrogation through stable transgenics. We plan to accomplish our overall objective by pursuing the following specific aims: (i) Generate high-quality near-isogenic lines (NILs), which differ from a parental species by only a single floral trait locus introgressed from another species, and use the NILs to genetically dissect each quantitative trait locus (QTL) underlying the pollination syndrome switches. (ii) Functionally characterize the causal genes and mutations under individual QTLs using stable transgenic experiments. (iii) Construct gene regulatory networks/modules that control pollination syndrome component traits using weighted gene co-expression network analysis. Results from this study are anticipated to provide an in-depth, genome-wide view of the causal genes underlying pollination syndrome switches, to identify a set of gene regulatory modules controlling individual floral traits that should be widely applicable in other plant systems, and to reveal novel molecular mechanisms that can inform studies of phenotypic evolution in not only plants, but also other organisms.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.