C2H2 zinc‐finger transcription factor FveJAG cooperates with SIMPLE LEAF1 to regulate compound leaf morphogenesis in strawberry

Leaves play a vital role in photosynthesis, respiration, and transpiration, significantly impacting a plant's adaptability and crop yield. Strawberry plants develop trifoliate compound leaves, the molecular regulatory pathways of which are not well-understood. Here, we identified a woodland strawberry (Fragaria vesca) mutant, designated simple leaf 2 (sl2), which exhibits the complete suppression of the two lateral leaflets. The causal gene encodes a C2H2 zinc-finger transcription factor that is homologous to JAGGED and is named FveJAG. A point mutation located within the intron triggers alternative splicing and generates a premature stop codon. The prior key transcriptional regulator of leaflet initiation, SIMPLE LEAF1 (SL1), directly targets the promoter of FveJAG to activate its transcription. The synergistic interaction between sl1 and sl2 indicates that SL1 and FveJAG function within the same regulatory pathway. Genetic and expression analyses suggest that FveJAG also acts downstream of FveMYB117a during leaflet initiation. Taken together, our results uncover a direct SL1 target gene and elucidate a complex regulatory network involving SL1, FveJAG, and FveMYB117a in strawberry compound leaf morphogenesis, offering further mechanistic insights into the genetic regulation of leaf complexity.