Identification and functional characterization of pineapple AcGPX5 in oxidative stress response

Pineapple (Ananas comosus), a globally significant crop, stands as the world's third most important tropical fruit. Throughout its extensive domestication history, mitotic recombination has contributed to the formation of terminal homozygosity regions on chromosomes. However, the functional genomic landscape and biological significance of these regions remain largely unexplored. In this study, we systematically investigated these regions. Functional enrichment analyses revealed that genes residing within these regions are predominantly associated with critical biochemical processes, including ADP binding, oxidoreductase activity, response to oxidative stress, and the catabolic metabolism of macromolecules. Utilizing transcriptomic profiling across fruit developmental stages, we classified these genes into five distinct clusters, each exhibiting unique expression patterns. Notably, genes within these clusters showed significant transcriptional dynamics during fruit ripening, suggesting a coordinated regulatory role in this process. Among these genes, AcGPX5, a cluster 1 gene, was identified as a strong candidate because of its markedly high expression levels during fruit development. To elucidate its functional role, we characterized AcGPX5 in terms of sequence architecture, predicted protein structure, and subcellular localization. Additionally, we conducted preliminary functional validation through enzyme activity assays and transgenic experiments. The enzyme activity assays confirmed that recombinant AcGPX5 possesses thioredoxin-dependent glutathione peroxidase activity, while multiple transgenic assays demonstrated that AcGPX5 plays an essential role in plant oxidative stress resistance. Collectively, this study identifies a set of ripening-related candidate genes embedded in chromosome terminal homozygosity regions and functionally characterizes AcGPX5 as a representative member. These findings advance our understanding of pineapple genome evolution and domestication and provide an experimental basis for exploiting these unique genetic resources in crop improvement.