Class III peroxidase genes in the moss Dicranum scoparium: Identification and abiotic stress induced expression analysis

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Class III peroxidases (POD: EC 1.11.1.7) are classical secretory plant peroxidases belonging to a large multigene family with diverse functions. Members of the POD family have been well-studied and characterized in many plants, including three species of bryophytes, but not from the moss Dicranum scoparium Hedw. Ecologically, D. scoparium is a very important species, which has a widespread distribution throughout the Holarctic. Here we present the first comprehensive report on the POD gene family in D. scoparium, identifying 22 genes encoding PODs (DsPODs), two of which were cloned for verification. All genes were deposited to GenBank under the third-party annotation (Accession numbers TPA: BK061169 – BK061190). Here, we present an in silico study of the physicochemical properties of these proteins. Analyses of conserved domains and subcellular localization suggested that DsPODs have classical peroxidase domain structure; they are secretory proteins and most of them are extracellular. Eight DsPODs highly homologous to Class III peroxidases from the mosses Pohlia nutans and Physcomitrium patens were further microcharacterized. All eight DsPODs possess a haem ligand and active sites necessary for enzymatic activity; they also contained sites for posttranslational modifications. Prediction of secondary structure indicated that these proteins mainly consist of α-helices and random coils. Experiments involving the reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) showed that DsPOD1, DsPOD2, DsPOD6, and DsPOD8 are differentially upregulated in response to stress. The stresses applied here included CdCl2, paraquat, unfavorable temperatures, and a hydration-desiccation-rehydration cycle. Our results indicate that Class III PODs contribute to the abiotic stress tolerance of D. scoparium, and specific DsPOD genes may play diverse roles in the response of the moss to stress.