Overexpression of a cytosolic ascorbate peroxidase from Panax ginseng enhanced salt tolerance in Arabidopsis thaliana

Ascorbate peroxidase (APX) plays an essential role in the antioxidant defense mechanism in the plant, serving in the ascorbate-glutathione cycle for the cellular H2O2 metabolism process. As the perennial plant, Panax ginseng Meyer encounters a lot of unfavorable growth conditions, and among them soil salinity significantly decreases the yield. Two APX genes from Panax ginseng were isolated and designated as PgAPX1 and PgAPX2, which are most similar with previously characterized cytosolic APX of Daucus carota and Spuriopimpinella brachycarpa, as revealed by sequence analysis of their deduced amino acid sequences. PgAPXs transcripts are most abundant in leaf tissue, whereas PgAPX1 expression level was higher compared to PgAPX2. Consistent with higher PgAPX1 expression during salt stress in ginseng, PgAPX1-overexpressing Arabidopsis lines (PgAPX1 (ox)) increased the germination rate and root length compared with wild-type (WT) under 200 mM NaCl stress treatment. Furthermore, higher chlorophyll content, relative water content, total APX activity, proline content, and lower H2O2 accumulation were shown in PgAPX1 (ox) plants compared to WT under 200 mM NaCl stress condition. Transcription analysis showed that PgAPX1 (ox) Arabidopsis lines were more salt-tolerant by upregulating the ion homeostasis mechanism.