关键词: 牡丹, 基因鉴定, AP2/ERF, 花发育, 基因组, 主成分分析, qRT-PCR

Abstract:

【Objective】 To investigate the roles of the AP2/ERF gene family in peony flower development and provide a theoretical foundation for the precise regulation of flower type breeding in peony. 【Method】 Using the peony genome as a reference, we systematically identified members of the AP2/ERF gene family and performed phylogenetic, gene structure, cis-element, and repeat event analyses. Genome sequences of Arabidopsis thaliana, rice, grape, and sweetgum were retrieved from public databases for interspecific synteny analysis using peony as the reference. RNA-seq datasets from various peony tissue types were obtained from global public repositories, processed by file segmentation and sequence alignment, and subsequently used to construct heatmaps with TBtools for functional prediction of AP2/ERF gene family members. Principal component and hierarchical clustering analyses were conducted to evaluate overall sample correlations. Tissue-specific expression patterns were further validated via quantitative real-time PCR (qRT-PCR) of 12 selected genes. 【Result】 A total of 126 AP2/ERF family members were identified and classified into four subfamilies (AP2, ERF, DREB, and RAV) and one unclassified group (Soloists) based on phylogenetic analysis. Synteny analysis revealed that 122 of these genes were anchored to the five chromosomes of peony, comprising 73 syntenic gene pairs. The number of homologous gene pairs between peony and sweetgum or grape was substantially higher than that between peony and Arabidopsis thaliana or rice, indicating a high degree of subfamily conservation, frequently accompanied by loss of the untranslated region (UTR). Cis-element analysis indicated that AP2/ERF family genes in peony are predominantly involved in plant growth and development, hormone signaling, abiotic stress responses, and light signal regulation. Expression profiling revealed that 48% of the 126 identified AP2/ERF members were associated with flower development. Twelve genes potentially related to flower development were identified, including three from the AP2 subfamily, six from the DREB subfamily, and three from the ERF subfamily. Using roots, stems, leaves, fully bloomed petals, and flower buds at five differentiation stages of the Fengdanbai cultivar as materials, qRT-PCR validation was performed. The results showed that 83% of these genes exhibited expression patterns consistent with RNA-seq predictions. 【Conclusion】 The expansion of the peony AP2/ERF gene family is attributed to both tandem and segmental duplications and occurred subsequent to the divergence between peony and Arabidopsis thaliana. In addition to members of the AP2 subfamily, certain genes from the ERF and DREB subfamilies also contribute to flower development in peony, highlighting a notable functional divergence of AP2/ERF family members in peony compared to other plant species.

Key words: peony, gene identification, AP2/ERF, flower development, genome, principal component analysis, qRT-PCR