Integrative transcriptomic and genome wide analysis reveals class III peroxidase responses to abiotic stresses in...

Selenicereus undatus (S.undatus) is an epiphyte cacti and it is largely grown in Asia. Drought, salinity and heavy metal stress are the major restricting factors in its growth and productivity in nature. Class III peroxidases (PODs) are important genes in response of plants to oxidative and abiotic stresses, as was found by a number of studies. Nevertheless, the genomic structure and functional analyses of POD genes in S. undatus have not been well investigated.

In this study, the physiological and molecular responses of Selenicereus undatus to single and multi-factorial environmental stresses were investigated in comparison with melatonin supplementation. However, stress significantly increased the activities of peroxidase (POD), proline content and hydrogen peroxide (H₂O₂) accumulation, which were strongly attenuated by the application of melatonin through maintaining an equilibrium in redox status to promote growth. Transcriptome analysis observed obvious differential expression in the HuPOD gene family when under different stress treatments. In the S. undatus genome 75 HuPOD genes were identified and classified into five phylogenetic subgroups. Among them, HuPOD-02/05/06/12/13/29 were strongly up-regulated under combined stress while HuPOD-36/56 showed slight downregulation to single stresses conditions. KEGG enrichment analysis revealed that under single and multi-factorial stresses, differentially expressed HuPOD genes were significantly enriched in the MAPK signaling pathway, glutathione metabolism, and phenylpropanoid biosynthesis, suggesting pivotal roles in oxidative stress regulation and signal transduction in S. undatus. RT-qPCR validation confirmed RNA-seq expression patterns for five representative genes (HuPOD-01/10/36/56/62), with HuPOD-10/62 showing the highest induction under melatonin-supplemented stresses (Cd+S+D+M).

These findings suggested that POD gene family may participate in the response to single and multifactorial stress in S.undatus This study provides a scientific basis for the further development and functional validation of the POD gene family in S.undatus.