Identification of genes involved in regulating terminal bud growth and death during long and short days in Paulownia

•Transcriptome profiles for Paulwonia terminal buds under different photoperiods provided evidence for the causes of terminal bud death and growth.•The genes of ABF, CYCD3, ERF1, and ARR-A are crucial for the regulation of terminal bud death.•TOC1 and LHY play an important role in the terminal bud growth of Paulwonia. The Paulownia is well-known for wood production and is called the tree of the future. A significant limitation of Paulownia cultivation is the "large crown and short stem" caused by the death of the terminal buds in autumn. In a previous study, we observed that the short day (SD, 8 h light and 16 h dark) results in the death of the terminal bud, whereas the long day (LD, 24 h light) results in sustained growth. To understand the molecular basis underlying this phenomenon, we conducted the RNA-Seq analysis of apical shoots in Paulownia under the SD and LD growth conditions for the three periods (2, 4, and 6 weeks). The metabolic pathways enrichment analysis was identified under the SD conditions, whereas the plant hormone signal transduction pathway plays an important regulatory role. After the cessation of growth, the ABF (a family of ABA-responsive element binding factors) in abscisic acid (ABA) signaling was downregulated. In addition, ERF1 in the ethylene (ETH) pathway, CYCD3 in the brassinosteroid (BR) pathway, and ARR-A in the cytokinin (CTK) pathway were upregulated. These may lead to reduced resistance of the terminal buds, continued cell division activity in the shoot apical meristem (SAM), and, ultimately, failure to form regular dormant buds. On the other hand, under LD conditions, TOC1 was upregulated, and LHYs were downregulated, along with genes involved in circadian rhythm, resulting in sustained growth. The findings help to elucidate the molecular mechanism of different photoperiods inducing terminal bud growth and death in the Paulownia species.