Evolutionary and Integrative Analysis of the Gibberellin 20-oxidase, 3-oxidase, and 2-oxidase Gene Family in Paeonia ostii: Insight into Their Roles in Flower Senescence

Abstract

The brief longevity of tree peony blossoms constrains its ornamental value and economic worth. Gibberellins (GAs) are crucial in the modulation of flower senescence, and GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox) catalyze the synthesis and deactivation of bioactive GAs. In Paeonia ostii, a total of three PoGA20ox, ten PoGA3ox, and twelve PoGA2ox proteins were identified and comprehensively analyzed. The analysis of the gene structures, conserved domains, and motifs revealed structural similarities and variances among the GA20ox, GA3ox, GA2ox-A, and GA2ox-B subfamilies. The synteny analysis indicated a scarcity of collinear blocks within the P. ostii genome, with no tandem or whole-genome duplication/segmental duplications found in PoGAoxs. The investigation into the binding of transcription factors to PoGAox promoters and the assessments of the expression levels suggest that PoGA2ox1 and PoGA2ox8.1 are promising candidate genes implicated in the regulation of floral senescence. Further, Pos.gene61099 (BPC6) and Pos.gene61094 (CIL2) appear to modulate PoGA2ox1 transcription in a positive and negative manner, respectively, while Pos.gene38359 (DDF1) and Pos.gene17639 (DREB1C) likely enhance PoGA2ox8.1’s expression. This study lays a foundation for an in-depth understanding of PoGAox functions and the development of strategies to delay flower senescence in tree peony.