Molecular cloning and potential function prediction of homologous SOC1 genes in tree peony

The central flower integrator PsSOC1 was isolated and its expression profiles were analyzed; then the potential function of PsSOC1 in tree peony was postulated. The six flowering genes PrSOC1, PdSOC1, PsSOC1, PsSOC1-1, PsSOC1-2, and PsSOC1-3 were isolated from Paeonia rockii, Paeonia delavayi, and Paeonia suffruticosa, respectively. Sequence comparison analysis showed that the six genes were highly conserved and shared 99.41% nucleotide identity. Further investigation suggested PsSOC1 was highly homologous to the floral integrators, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), from Arabidopsis. Phylogenetic analysis showed that the SOC1 protein clustering has family specificity and PsSOC1 has a close relationship with homologous SOC1 from Asteraceae species. The studies of PsSOC1's expression patterns in different buds and flower buds, and vegetative organs indicated that PsSOC1 could express in both vegetative and reproductive organs. While the expression of PsSOC1 in different developmental stages of buds was different; high expression levels of PsSOC1 occurred in the bud at the bud sprouting stage and the type I aborted the flower bud. PsSOC1 expression was also shown to be affected by gibberellins (GA), low temperature, and photoperiod. One of the pathways that regulates tree peony flowering may be the GA-inductive pathway. Ectopic expression of PsSOC1 in tobacco demonstrated that greater PsSOC1 expression in the transgenic tobacco plants not only promoted plant growth, but also advanced the flowering time. Finally, the potential function of PsSOC1 in tree peony was postulated.