Genome wide identification and expression analysis of gibberellin oxidase family genes in sweet potato and its two diploid relatives

As essential plant hormones, gibberellins (GAs) regulate various growth and development processes. GA oxidases (GAoxs), including the GA2ox, GA3ox, and GA20ox subgroups, play prominent roles in the synthesis and degradation of GA; however, a systematic analysis of GAoxs has not been reported in sweet potato. Here, we identified GAox genes based on a comparative genomic analysis in sweet potato (I.batatas) and its two diploid wild relatives I. trifida and I. triloba. A total of 71 GAox genes were identified, with 23 in sweet potato, 25 in I. trifida and 23 in I. triloba. These genes can be divided into four phylogenetic groups based on their protein sequences. Each subgroup had their own conserved motif combination. The prediction of cis-elements in the promoter region showed that the most numerous elements in the promoter regions were related to hormone response. GAox genes in sweet potato respond to both plant hormones and abiotic stresses; notably, gene expression and co-expression analysis implicated ibGA2ox10 in tuber expansion, ibGA20ox3/ibGA3ox5 in indole-3-acetic acid (IAA) and gibberellin (GA) synergy, ibGA2ox5/ibGA3ox7 in gibberellin (GA) and paclobutrazol antagonism, and ibGA20ox1/ibGA3ox8 in abiotic stress response.