Two LEAFY homologs regulate floral patterning and development without affecting flowering time in kiwifruit

Actinidia chinensis (kiwifruit) are economically important fruit-bearing woody perennial vines, but with a long juvenile phase which slows plant breeding efforts. LEAFY (LFY) encodes a plant specific transcription factor central to the reproductive pathway in many plants, and its overexpression can accelerate flowering including in some trees. We identified two kiwifruit LFY (AcLFY) genes, expressed in actively-growing apical buds. Overexpression of AcLFY1 or AcLFY2 promoted flowering in Arabidopsis, but did not accelerate flowering in kiwifruit. Instead, branching at the lower nodes and changes in leaf morphology were observed. CRISPR-Cas9 targeted mutagenesis of AcLFY1 and/or AcLFY2 in a fast-flowering hermaphrodite kiwifruit background generated single and double mutants. The mutants flowered at the same time as control lines. Single mutants developed normal flowers, but double knockout mutations had severe effects on floral patterning and floral organ development. Petals and stamens were strongly affected, impacting on self-pollination, fruit size and shape. RNA-seq showed the two AcLFY genes were differentially regulated by the expression of floral repressors AcCENTRORADIALIS genes. These results suggest that the AcLFY genes control plant architecture and contribute together to floral organ development and floral patterning which has implications for successful pollination and fruit set in kiwifruit.