A Specific Gibberellin 20-Oxidase Dictates the Flowering-Runnering Decision in Diploid Strawberry

Abstract

Asexual and sexual reproduction occur jointly in many angiosperms. Stolons (elongated stems) are used for asexual reproduction in the crop species potato (Solanum tuberosum) and strawberry (Fragaria spp), where they produce tubers and clonal plants, respectively. In strawberry, stolon production is essential for vegetative propagation at the expense of fruit yield, but the underlying molecular mechanisms are unknown. Here, we show that the stolon deficiency trait of the runnerless (r) natural mutant in woodland diploid strawberry (Fragaria vesca) is due to a deletion in the active site of a gibberellin 20-oxidase (GA20ox) gene, which is expressed primarily in the axillary meristem dome and primordia and in developing stolons. This mutation, which is found in all r mutants, goes back more than three centuries. When FveGA20ox4 is mutated, axillary meristems remain dormant or produce secondary shoots terminated by inflorescences, thus increasing the number of inflorescences in the plant. The application of bioactive gibberellin (GA) restored the runnering phenotype in the r mutant, indicating that GA biosynthesis in the axillary meristem is essential for inducing stolon differentiation. The possibility of regulating the runnering-flowering decision in strawberry via FveGA20ox4 provides a path for improving productivity in strawberry by controlling the trade-off between sexual reproduction and vegetative propagation.

Mechanism of auxin and GA crosstalk in diploid strawberry fruit initiation

“…The rga1-1 (u230) mutant was previously generated by ENU chemical mutagenesis in a ga20ox4 loss of function mutant background (Tenreira et al, 2017; Caruana et al, 2018). This rga1-1; ga20ox4 was backcrossed with WT (H4) to yield rga1-1 single mutant, which was used in all analyses.…”

A roadmap for research in octoploid strawberry

“…The R locus was also recently mapped, and a mutation in a gene encoding gibberellin (GA) biosynthetic enzyme GA20-oxidase (FvGA20ox4) was found. This gene is highly expressed in axillary buds, and the mutated enzyme is not able to convert GA12 to GA20, a precursor of bioactive GA1 75 .…”

“…Inhibitors of GA biosynthesis, in contrast, enhance crown branching and yield in cultivated strawberry 89,90 . Furthermore, FvSOC1 was found to control runner formation and regulate the expression of several GA biosynthetic genes, including the recently identified FvGA20ox4, which likely encodes a rate limiting enzyme of the GA biosynthetic pathway in axillary buds 75,78 . These data suggest a model in which FvSOC1 activates FvGA20ox4 and possibly other GA biosynthetic genes in axillary buds, leading to high bioactive GA1 levels, degradation of SLR proteins, and runner formation (Fig.…”

A Time to Divide and a Time to Expand: Histone Deacetylases Flip a Gibberellin Oxidase-Mediated Switch in Root Meristem Cells

“…29: 2082-2083, September 2017, www.plantcell.org 2017 development (Tenreira et al, 2017; also see Lockhart, 2017). Therefore, surveying and integrating the functions of GA oxidases will improve our understanding of plant development.…”