Overexpression of ATHG1/AHL23 and ATPG3/AHL20, Arabidopsis AT-hook motif nuclear-localized genes, confers salt tolerance in transgenic Zoysia japonica

Zoysia japonica Steud. is a native turfgrass in the Korean peninsula and is used worldwide. Abnormal conditions of soil salinity inhibit plant growth and adversely affect the quality of the turfgrass. AT-hook motif nuclear-localized (AHL) family proteins known to co-regulate the transcription of genes as a chromatin remodeling factor play a role in plant developmental processes and stress responses. In this study, AT - Hook Protein of Genomine 1 ( ATHG1 ) /AT - Hook motif nuclear - Localized protein 23 ( AHL23 ) and AT - hook Protein of Genomine 3 ( ATPG3 ) /AT - Hook motif nuclear - Localized protein 20 ( AHL20 ), two AHL genes from A. thaliana , were transformed into Z. japonica under the control of a constitutive ubiquitin promoter. Southern blot analysis proved that ATHG1/AHL23 and ATPG3/AHL20 were introduced into the ATHG1/AHL23 -transgenic plants and ATPG3/AHL20 -transgenic plants, respectively. Overexpression of each ATHG1/AHL23 and ATPG3/AHL20 in all of the transgenic plants was confirmed by quantitative real-time PCR (qRT-PCR). To evaluate a tolerant response to salt stress of the transgenic plants, 4 transgenic plants including ATHG1 -overexpressing line 1 ( ATHG1 -OE1) and ATHG1 -OE2, and ATPG3 -overexpressing line 1 ( ATPG3 -OE1) and ATPG3 -OE2 were selected, respectively. All the transgenic plants showed higher salt-tolerant phenotype with higher chlorophyll and lower malondialdehyde (MDA) contents under salt treatment, compared to the wild types. Also, under salt treatment, the transgenic plants revealed higher activities of catalase (CAT) and peroxidase (POD), reactive oxygen species (ROS)-scavenging enzymes, than those of the wild-type plant. These results suggest that overexpression of ATHG1/AHL23 or ATPG3/AHL20 belonging to the AHL gene family confers salt tolerance to the transgenic zoysiagrass plants.