The SUPERMAN orthologous Genes PaSUP1/2/3 of Platanus × acerifolia Have Functional Differentiation in Transgenic Arabidopsis

Abstract The gene SUP (SUPERMAN) encodes a transcription factor that plays an important role in floral organ development in Arabidopsis thaliana. There are three SUP orthologous genes PaSUP1/2/3 in London plane (Platanus × acerifolia) that contain two conserved domains involving C2H2-type zinc finger motif and EAR-like repression motif. The spatial expression pattern of PaSUP1 indicated its sex-specific expression at female inflorescences, while the temporal expression pattern in flower-bud reflected its role in the differentiation of unisexual flowers. Nevertheless, other two orthologous genes PaSUP2/3 had inactive expression patterns around the year. The subcellular localizations of PaSUP1/2/3 implied 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 abnormal leaf phenotype. In 35S::PaSUP1 transgenic Arabidopsis and tobacco, floral organs were smaller than wild-type and the outer three whorls had been more strongly suppressed compared to the fourth whorl. The epidermal cells on floral organs of 35S::PaSUP1 transgenic Arabidopsis were smaller than wild-type through scanning electron microscopy observation. Transcriptome analysis at inflorescences of 35S::PaSUP1 transgenic Arabidopsis indicated that anther and pollen developmental related genes were significantly downregulated. Meanwhile, the yeast two-hybrid assay and BiFC analysis demonstrated interactions between PaSUP1 and TFL2, which may lead to the downregulation of auxin-related genes YUC1/4 in inflorescences of transgenic Arabidopsis. Moreover, transgenic Arabidopsis with pPI::PaSUP1 showed normal vegetative growth without fruits. In the future, PaSUP1 transgenic modification in London plane may help to cultivate sterile germplasm, which can solve problems of pollen allergy and seed hairs in practical applications.