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Control of development is an important issue in the production of ornamental plants. Gibberellins (GAs) play a key role in regulating plant growth and development. DELLA is nuclear negative regulators of GA signaling. We identified two DELLA homologous genes, PmDELLA1 and PmDELLA2, in the genome of mei (Prunus mume) genome. We analyzed the structure, expression patterns and molecular functions of both genes. Tissue expression analysis showed that both genes were transcriptionally active. PmDELLA1 showed higher expression in seeds than PmDELLA2. This indicated that PmDELLA2 plays different roles from PmDELLA1 in seed germination. The expressions of both genes at various flowering stages were relatively low. We speculated that PmDELLAs might be positive regulators of flowering by releasing the repression of GA during floral blooming. Transgenic arabidopsis (Arabidopsis thaliana) lines overexpressing the two genes showed dwarf and delayed flowering. We confirmed that the two PmDELLAs were partially conserved with genes encoding DELLA proteins in arabidopsis. Our bioinformatics and functional analyses provide information that may be valuable to improve the economic, agronomic and ecological properties of mei and other Rosaceae fruit trees.
The MADS-box gene SOC1/TM3 (suppressor of overexpression of constans 1/tomato MADS-box gene 3) integrates multiple flowering signals to regulate the transition from vegetative to reproductive development in arabidopsis (Arabidopsis thaliana). Although SOC1-like genes have been isolated from a wide range of plant species, their orthologs are not well characterized in mei (Prunus mume), an important ornamental and fruit plant in east Asia. To better understand the molecular regulation of flower development in mei, we isolated and characterized three putative orthologs of arabidopsis SOC1, including PmSOC1-1, PmSOC1-2, and PmSOC1-3. The phylogenetic tree revealed that these genes fall into different subgroups within the SOC1-like gene group, suggesting distinct functions. PmSOC1-1 and PmSOC1-3 were mainly expressed in vegetative organs and at low expression levels in floral parts of the plants, whereas PmSOC1-2 was expressed only in vegetative organs. Furthermore, the expression level decreased significantly during flower bud differentiation development, suggesting a role for these genes in the transition from the vegetative to the reproductive phase. Overexpression of PmSOC1-1, PmSOC1-2, and PmSOC1-3 in arabidopsis caused early flowering. Early flowering also increased expression levels of four other flowering promoters, agamous-like 24 (AGL24), leafy (LFY), apetala 1 (AP1), and fruitfull (FUL). Moreover, the overexpression of PmSOC1-1 and PmSOC1-2 resulted in a range of floral phenotype changes such as sepals into leaf-like structures, petal color into green, and petal into filament-like structures. These results suggested that the genes PmSOC1-1, PmSOC1-2, and PmSOC1-3 play an evolutionarily conserved role in promoting flowering in mei, and may have distinct roles during flower development. Our findings will help elucidate the molecular mechanisms involved in the transition from vegetative to reproductive development in mei.