Molecular framework underlying stolon development in strawberry

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Strawberry is an immensely important fruit crop contributing to human nutrition and agricultural output. As current strawberry varieties are all derived from traditional crossbreeding efforts, they need to be propagated through daughter clones to preserve their unique hybrid combination. These daughter clones, known as runners, are produced from long and hortizontal stems named stolons. However, little is known about how stolon formation is regulated and why strawberry is one of the few plants endowed with the molecular machinery to conduct asexual reproduction through stolon. The experiments are aimed at revealing the molecular mechanisms that underlie this special and highly important developmental trait of strawberry. Further, the project will train next generation scientists in critical thinking, communication, as well as experimental design and execution. Additionally, a professor at the Virginia State University will bring two undergraduate students to the University of Maryland each summer to learn DNA sequence analysis and conduct research. Overall, the project will provide knowledge base and tools to switch on and off stolon, leading to improved strawberry production when stolon formation is switched on or increased fruit yield when stolon formation is turned off. The data generated from the project such as RNA sequence data and network analyses will be easily accessible through websites and public depository; the research materials will be shared with the scientific community. The results will advance basic understanding of plant development and provide novel strategies in the improvement of strawberry productivity. In strawberry, the interesting mode of asexual reproduction through stolon provides an unusual opportunity to investigate axillary meristem cell fate determination as each axillary meristem either develops into a stolon or a branch crown (a shoot that terminates with flowers). Previous studies using a diploid strawberry Fragaria vesca identified a key signaling component of gibberellin, FveRGA1, as a repressor of stolon formation. The experiments will investigate the mechanism of how FveRGA1 represses stolon formation in F. vesca by first isolating null alleles of FveRGA1 with CRISPR and then characterizing the mutant phenotype. Transcriptome and consensus co-expression networks will identify genes expressed in the axillary meristem that gives rise to stolon. Proteins that directly interact with FveRGA1 in the axillary meristem will be identified through a yeast two-hybrid screen and confirmed by Bimolecular Fluorescence Complementation. The role of identified candidate genes in stolon development will be determined using RNAi and over-expression in transgenic F. vesca. Finally, forward genetic approach will be used to map and isolate genes defined by new mutants with altered ability in stolon formation. These experiments will provide novel insights into the molecular underpinnings of stolon development and illuminate the mechanisms of molecular interaction between the identified genes and FveRGA1 in controling stolon formation. The ablity to suppress stolon production will maximize branch crown formation, leading to more flowers and higher fruit yield. Insights derived from this project will provide knowledge and tools to switch on and off stolon, leading to improved strawberry production and yields.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.