The SUPERMAN orthologous genes PaSUP1/2/3 of Platanus × acerifolia have functional differentiation in transgenic Arabidopsis

The gene SUP (SUPERMAN) encodes a transcription factor that plays an important role in floral organ development in Arabidopsis thaliana. In the London plane (Platanus × acerifolia), there are three SUP orthologous genes PaSUP1/2/3, which encode two conserved domains, namely the C2H2-type zinc finger motif and the EAR-like repression motif. The spatial expression pattern of PaSUP1 indicated its sex-specific expression in the female inflorescence, while the temporal expression pattern in flower-bud reflected its role in the differentiation of unisexual flowers. However, the other two orthologous genes PaSUP2/3 showed inactive expression patterns throughout the year. The subcellular localizations of PaSUP1/2/3 suggested that they were more than nuclear-localized. Both 35S::PaSUP1 transgenic Arabidopsis and tobacco showed developmental defects in floral organs similar to the ectopic expression of SUP, whereas 35S::PaSUP2/3 transgenic Arabidopsis showed only an abnormal leaf phenotype. In 35S::PaSUP1 transgenic Arabidopsis and tobacco, floral organs were smaller than wild-type and the outer three whorls were more strongly suppressed compared to the fourth whorl. The epidermal cells on floral organs of 35S::PaSUP1 transgenic Arabidopsis were smaller than wild-type as observed by scanning electron microscopy. Transcriptome analysis of inflorescences of 35S::PaSUP1 transgenic Arabidopsis showed that the expression of genes related to anther and pollen development was significantly downregulated. Meanwhile, the yeast two-hybrid assay and BiFC analysis revealed interactions between PaSUP1 and TFL2, which may lead to the downregulation of auxin-related genes YUC1/4 in inflorescences of transgenic Arabidopsis. In addition, transgenic Arabidopsis with pPI::PaSUP1 showed normal vegetative growth without fructification. In the future, the PaSUP1 transgenic modification in London plane may help to produce sterile germplasm that can solve pollen allergy and seed hair problems in practical applications.