Summary: The genes that encode the ethylene biosynthesis enzyme 1‐aminocyclopropane‐1‐carboxylate oxidase (ACO) are thought to be involved in flower senescence. Hence, we investigated whether the transcript levels of PhACO genes (PhACO1, PhACO3 and PhACO4) in Petunia cv. Mirage Rose are associated with ethylene production at different flowering stages. High transcript levels were detected in the late flowering stage and linked to high ethylene levels. PhACO1 was subsequently edited using the CRISPR/Cas9 system, and its role in ethylene production was investigated. PhACO1‐edited T₀ mutant lines, regardless of mutant type (homozygous or monoallelic), exhibited significantly reduced ethylene production and enhanced flower longevity compared with wild‐type. Flower longevity and the reduction in ethylene production were observed to be stronger in homozygous plants than in their monoallelic counterparts. Additionally, the transmission of the edited gene to the T₁ (lines 6 and 36) generation was also confirmed, with the results for flower longevity and ethylene production proving to be identical to those of the T₀ mutant lines. Overall, this study increases the understanding of the role of PhACO1 in petunia flower longevity and also points to the CRISPR/Cas9 system being a powerful tool in the improvement of floricultural quality.

Roses (Rosa hybrida) are a highly merchandised flower but lack blue varieties. Overexpression of the flavonoid 3′,5′-hydroxylase (F3′5′H) gene can increase the accumulation of blue pigment (delphinidin anthocyanin). However, sometimes the effect of F3′5′H gene alone is inadequate for producing blue flowers. Furthermore, the internal environment of the cell, such as an increase in pH, can also help the conversion of anthocyanins to blue pigments. Nonetheless, genetic engineering methods can simultaneously introduce multiple genes at the same time to regulate the development of blue pigments to achieve the ultimate breeding goal of producing blue color in roses. In the present study, to simultaneously adjust the accumulation of delphinidin and vacuolar pH, we introduced the Viola tricolor flavonoid 3′,5′-hydroxylase (VtF3′5′H) and Rosa hybrida Na+/H+ exchanger (RhNHX) genes into the white rose line “KR056002” using Agrobacterium-mediated transformation. The quantitative real time polymerase chain reaction (qRT-PCR) results showed that the heterologous genes in the transgenic lines were highly expressed in petals and leaves, and simultaneously promoted the expression of related anthocyanin synthesis structural genes. Obvious color changes were observed in both petals and young leaves, especially when petals changed from white to red-purple. The formation of delphinidin was not detected in the petals of control plants, whereas the petals of transgenic lines had higher delphinidin content (135–214 μg/l) and increased pH value (0.45–0.53) compared with those of control plants.

We examined the effects of different sucrose concentrations (3%, 5%, and 7%) on anthocyanin accumulation and plant growth in wild type (WT) and transgenic (T₂) torenia cultivar “Kauai Rose” overexpressing the anthocyanin regulatory transcription factors B-Peru + mPAP1 or RsMYB1. Sucrose increased anthocyanin production in both WT and transgenic plants, with higher anthocyanin production in transgenic plants compared to WT plants. Higher sucrose concentrations increased production of anthocyanin in transgenic and WT plants, with increased anthocyanin production associated with increased expression of anthocyanin biosynthesis genes. Higher sucrose concentrations reduced growth of WT and transgenic plants. Our results indicate that sucrose enhances anthocyanin production in torenia by regulating anthocyanin biosynthesis genes.