FvCYCA1 participates in the petal development of Fragaria vesca

Flower is the characteristic ornamental organ of plants, and its growth and development are associated with cell division and differentiation. Arabidopsis CYCA1;2 has a role in the first meiotic division, while its function in the growth of floral organs largely remains unknown. Here we identify the Fragaria vesca homolog FvCYCA1 and investigate its function in petal development of strawberry. FvCYCA1 localizes in the nucleus, and it has high expression in most tissues especially flowers. FvCYCA1 transcription in petals is negatively correlated with petal development in multiple diploid woodland strawberry varieties and at different developmental stages of petals in the variety of 'Hawaii-4 & PRIME;. Cytological analysis of petals indicates negative correlations between FvCYCA1 transcription and cell area or cell numbers in petals. Heterologous overexpression of FvCYCA1 in Arabidopsis reduces the cell area and cell number in petals consequently inhibiting petal development. Knocking out of CYCA1;2 in Arabidopsis using CRISPR-Cas9 technology results in increased cell area and cell number in leaves and petals consequently leading to enlarged leaf and petal sizes, all of which are complemented by overexpressing FvCYCA1 in Arabidopsis mutants. Nuclear DNA ploidy level analyses reveal overexpression of FvCYCA1 represses endocycle in Arabidopsis leaves and petals, which counteracts the promotion effects observed in Arabidopsis cyca1;2 mutants. Furthermore, overexpressing FvCYCA1 in 'Hawaii-4 & PRIME; results in same effects on petal and leaf development as that in Arabidopsis. Taken together, our results illustrate that FvCYCA1 is a functional homolog of that in Arabidopsis, and negatively regulates petal development through the modulation of cell cycle.