The floral transition in Chinese cabbage (Brassica rapa ssp. pekinensis) is governed by a complex interplay of gene expression and hormonal regulation. Temporal transcriptome profiling was conducted across three developmental stages: pre-bolting (PBS), bolting (BS), and flowering stages (FS), to investigate the underlying molecular mechanisms. A total of 7092 differentially expressed genes (DEGs) were identified, exhibiting distinct expression trajectories during the transition. Moreover, functional enrichment analyses revealed strong associations with plant hormone signaling, MAPK pathways, and developmental regulation processes. Key flowering-related genes, such as BrFLM, BrAP2, BrFD, BrFT, and BrSOC1s displayed antagonistic expression patterns. Hormonal pathways involving auxin, ABA, ET, BR, GA, JA, CK, and SA showed stage-dependent modulation. Further, orphan genes (OGs), especially EARLY FLOWERING 1 (EF1), showed significant upregulation during the transition, which exhibited 1.84-fold and 1.93-fold increases at BS and FS compared to PBS, respectively (p < 0.05). Functional validation through EF1 overexpression (EF1OE) in Arabidopsis consistently promoted early flowering. The expression levels of AtFT and AtSOC1 were significantly upregulated in EF1OE lines compared to wild-type (WT) plants. The findings contribute to understanding the coordinated genetic and hormonal events driving floral development in Chinese cabbage, suggesting EF1 as a candidate for bolting resistance breeding. This work also expands the existing regulatory framework through the successful integration of OGs into the complex floral induction system of Brassica crops.

Orphan genes (OGs) lack homologs in related species and have been associated with adaptive evolution. However, it is poorly characterized in Brassica napus (rapeseed). This study aims to identify and characterize OGs in rapeseed to evaluate their association with stress adaptation and lineage-specific traits. Through comprehensive comparative genomics analysis, all rapeseed genes were categorized into four distinct evolutionary classes. Furthermore, bioinformatics analyses were carried out to evaluate the structural, evolutionary, and expression dynamics, which were further validated by qRT-PCR analysis of different tissues and in cold stress. In total, 4 B. napus OGs (BnaOGs), 2859 Brassica-specific genes (BSGs), 9650 Cruciferae-specific genes (CSGs), and 94,720 evolutionarily conserved genes (ECGs) were identified. BnaOGs and BSGs indicated shorter sequences, higher GC content, fewer transcription factors, and limited functional annotation compared to ECGs. Similarly, transcriptomic analysis determined the tissue-specific and stress-responsive expression patterns in BnaOGs and BSGs. qRT-PCR validation revealed four BnaOGs and five BSGs from different tissue-specific and cold-responsive expression modules in rapeseed. Overall, this study identified OGs associated with lineage-specific adaptation in rapeseed, potentially related to cold tolerance and phenotypic diversity. The identified expression patterns and structural divergence provide novel insights for breeding stress-resilient varieties.