The B-class of MADS-box transcription factors has been studied in many plant species, but
remain functionally uncharacterized in the Rosaceae family. APETALA3 (AP3), a member of this
class, controls the identity of petals and stamens in Arabidopsis thaliana. In this work, we identified
two members of the AP3 lineage in the cultivated strawberry (Fragaria × ananassa): FaAP3
and FaTM6. Interestingly, FaTM6, and not FaAP3, shows an expression pattern equivalent to that
of AP3 in Arabidopsis. Genome editing using Cluster Regularly Interspaced Short Palindromic
Repeats (CRISPR)/Cas9 system is becoming a robust tool for targeted and stable mutagenesis
of DNA. However, whether it can be efficiently used in an octoploid species such as F. × ananassa
is not known. In our study, we report the application of the CRISPR/Cas9 in F. × ananassa to
characterize the function of FaTM6 in flower development. An exhaustive analysis by high-throughput
sequencing of the FaTM6 locus spanning the target sites showed a high efficiency genome
editing already in the T0 generation. The phenotypic characterization of the mutant lines
indicates that FaTM6 plays a key role in petal and especially in anther development in strawberry.
Our results validate the CRISPR/Cas9 strategy for gene functional analysis in an octoploid
species such as F. × ananassa, and offer new opportunities for engineering strawberry to improve
traits of interest in breeding programs.
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