Topping-induced transcriptome changes reveal PaSPL-mediated regulation of plant architecture in Platanus acerifolia

Plant architecture is one of the most important qualities of Platanus acerifolia Willd., enabling it to be known as "the king of street trees". However, there are few reports available on its molecular regulatory mechanisms. Shoot branching is a key process in regulating plant architecture. In this study, topping experiments and transcriptome sequencing analyses were performed to elucidate the molecular mechanisms underlying axillary bud growth and development in P. acerifolia. After 3 d of topping, the axillary buds in P. acerifolia exhibited significant growth, with the trend increasing over subsequent days. The KEGG enrichment analysis revealed considerable changes in the expression levels of genes involved in the auxin signal transduction pathway. Additionally, the expression of most PaSPL genes was downregulated after topping. While Pla-miR156f regulated Arabidopsis plant architecture, flowering transition and flower development, this regulation was not directly influenced by the topping pathway. These results contribute to a better understanding of P. acerifolia plant architecture regulation and provide valuable insights into the regulation of other plants, particularly woody plants.