Molecular mechanisms underlying the determination of axillary bud fate and outgrowth into branch crown in strawberry

Summary ▪ In strawberry, the axillary bud (AXB) can produce either an elongated stem called stolon giving a daughter-plant (asexual reproduction) or an inflorescence-bearing branch crown (BC) (sexual reproduction). The fate of the AXB depends on node position on the axis and on genetic and environmental factors. Here, in Fragaria vesca , we addressed the largely unanswered question of how molecular factors determine AXB fate. ▪ To get insights into the mechanisms already at play in a morphologically indistinguishable (undifferentiated) AXB, depending on its fate, we combined (1) the phenotypic characterization of AXB development throughout plant growth with (2) the RNA-seq analysis of undifferentiated AXBs, using three different genotypes producing either BCs or stolons ( fvetfl1 and fvega20ox mutants, FveFT3 overexpressor). ▪ Results allowed the identification of genes regulating AXB fate and outgrowth, among which FveBRC1 . The analysis of FveBRC1 expression in genotypes combining various traits (perpetual/seasonal flowering; runnering/runneless) and the generation of CRISPR/Cas9 brc1 mutants further demonstrated that FveBRC1 plays a central role in the determination of AXB fate in strawberry, in addition to its well-known function in BC outgrowth. ▪ These original results provide new insights into the determination of AXB fate and, consequently, the control of fruit yield in strawberry.