Identification and characterization of the Chenopodium quinoa gibberellin oxidase gene family and its role in seed germination

Abstract

Pre-harvest sprouting (PHS) is an urgent problem in the quinoa breeding process. Gibberellin oxidases are key enzymes in the biosynthesis and degradation of gibberellins, playing a significant role in the regulation of active gibberellins (GAs). In this study, 18 CqGAox genes were identified in quinoa and characterized according to phylogenetic relationships, gene structure, conserved motifs, codon use pattern, and expression patterns. Based on their phylogenetic relationships, the CqGAox genes were classified into four groups: C19CqGA2ox, C20CqGA2ox, CqGA3ox, and CqGA20ox. Evolutionary analyses showed that homologous GAox genes from Arabidopsis, rice, and quinoa have been subject to purifying selection during evolution. According to the codon use patterns, mutational stress may cause codon bias in CqGAox genes. Prediction of promoter cis-regulatory elements suggested that the CqGAox genes contained multiple elements that responded to phytohormones and stress. We further evaluated the transcriptional responses of CqGAox genes during quinoa seed germination and under low-temperature stress treatments of seedlings. Moreover, qRT-PCR was used to confirm the changes in CqGAox gene expression during quinoa seed germination under GA₃ and paclobutrazol (PAC) treatments. Compared with the control, expression of CqGAox genes was significantly altered by treatment with GA₃ or PAC. These findings indicated that the CqGAox genes are essential for regulating GA biosynthesis and degradation. This study lays the foundation for further investigations of the roles of CqGAox genes in GA-regulated quinoa seed germination and provides potential targets for addressing the challenge of quinoa PHS.