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 genes that are 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. We used CRISPR-Cas9 targeted mutagenesis of LFY1 and/or LFY2 in a fast-flowering hermaphrodite kiwifruit background to generate single- and double-mutants, which flowered at the same time as control lines. However, whilst single-mutants developed normal flowers, double-knockout mutations had severe effects on floral patterning and floral organ development. Petals and stamens were strongly affected, impacting on self-pollination, and fruit size and shape. RNA-seq showed that the two LFY genes were differentially regulated via the expression of CENTRORADIALIS genes that encode floral repressors. Our results suggest that the LFY 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.