Genome-wide identification and expression analysis of ACS and ACO gene family in Ziziphus jujuba mill during fruit ripening

The jujube (Ziziphus jujuba Mill.) cultivar 'Dongzao' is globally popular as a fresh fruit but faces challenges with shelf life, which is positively associated with ethylene production. The two key enzymes involved in ethylene biosynthesis, 1-Aminocyclopropane-1-Carboxylic acid Synthase (ACS) and 1-Aminocyclopropane-1-Carboxylic acid Oxidase (ACO), are encoded by ACS and ACO gene families, respectively. This study identified 7 ZjACS genes and 36 ZjACO genes in 'Dongzao' and revealed extensive evolutionary divergence between 'Dongzao' and Arabidopsis thaliana. Phylogenetic relationships were more apparent when analyzing genes with similar structures, motifs and subcellular localization predictions. Transcriptome profiling showed that a substantial number of the ZjACS and ZjACO genes displayed stage-specific expression tendency during fruit development. Co-expression analysis showed that 4 ZjACS and 9 ZjACO genes were linked to transcription factors (TFs) involved in fruit ripening. The diverse regulatory factors, including ERF, NAC and WRKY TFs and cis-acting regulatory elements, likely contribute to the complex roles of the ZjACSs and ZjACOs during ripening of jujube fruits. This study sheds light on the genetic regulation of ethylene biosynthesis in 'Dongzao' jujube ripening, providing insights for postharvest research in this economically important species.