The MIKC-type MADS-box (MIKC) gene family is essential for controlling various plant developmental processes, including flowering time and dormancy transitions. Although the MIKC gene family has been widely studied across different plants, its characterization and functional study in herbaceous peony remain limited. In this study, 19 Paeonia lactiflora Pall. MIKC-type (PlMIKC) genes were identified from the transcriptome of a low-chilling requirement Paeonia lactiflora Pall. cultivar ‘Hang Baishao’. These MIKC genes were categorized into seven clades: six were classified as MIKC^C-type, including FUL/AP1, DAM, PI, AGL18, AGL12, AG, and SOC1, and one, AGL30, was classified as MIKC*-type. Notably, the FLC clade genes were absent in Paeonia lactiflora Pall. The PlMIKC genes were predominantly localized to the nucleus, and their sequences contained highly conserved MADS and K-domains. Phylogenetic analysis demonstrated that PlMIKC genes share a strong evolutionary affinity with the MIKC genes from grapevine (Vitis vinifera) and poplar (Populus trichocarpa). A low-temperature-induced bud dormancy transition (BDT) experiment revealed that PlMIKC genes, such as PlFUL and PlDAM, were highly expressed during dormancy maintenance, while PlSOC1, PlAGL12, and PlAGL30 were upregulated during BDT. Additionally, the transient overexpression of PlSOC1 in ‘Hang Baishao’ significantly accelerated BDT and promoted bud break, suggesting that SOC1, traditionally linked to flowering regulation, also plays a key role in dormancy transition. Since limited literature on the MIKC gene family is currently available in herbaceous peony, this study expands the knowledge of the MIKC genes in Paeonia lactiflora Pall. and offers valuable insights into the molecular regulation of bud dormancy in response to low temperatures.

Grafting involves complex hormonal interactions at graft interfaces that are not yet fully understood. In this study, we analyzed hormone fluctuations and gene expression during callus proliferation and vascular tissue differentiation in hickory (Carya cathayensis Sarg.) grafts. Cytokinin and ethylene precursor ACC levels steadily increased after grafting. The biosynthetic genes for these hormones (IPT3, ACS1, ACO1, and ACO5) exhibited heightened expression. Genes related to cytokinin signaling (RR3, ARR4, and ZFP5) and ethylene signaling (MKK9, ESE1, and ESE3) were similarly upregulated. Conversely, genes associated with jasmonic acid, abscisic acid, and strigolactone pathways were downregulated, including synthesis genes (AOC4 and AOS) and those involved in signal transduction (NAC3, WRKY51, and SMAX1). Correspondingly, JA-Ile and 5-deoxystrigol levels significantly decreased. Indole-3-acetic acid (IAA) levels also dropped during the early stages of graft union formation. These results suggest that low auxin concentrations may be essential in the initial stages after grafting to encourage callus proliferation, followed by an increase at later stages to facilitate vascular bundle differentiation. These findings imply that maintaining a balance between low auxin levels and elevated cytokinin and ethylene levels may be critical to support cell division and callus formation during the initial proliferation phase. Later, during the vascular differentiation phase, a gradual rise in auxin levels, accompanied by elevated ethylene, may facilitate the differentiation of vascular bundles in hickory grafts.