Involvement of a cucumber MAPK gene (CsNMAPK) in positive regulation of ROS scavengence and osmotic adjustment under salt stress

Mitogen-activated protein kinase (MAPK) cascades play a key role in plant growth and development as well as biotic and abiotic stress response. To unravel the roles of MAPK in cucumber, its expression in transgenic cucumber plants was reduced by an antisense approach. For this purpose, a 1113 bp cDNA fragment of cucumber MAPK gene (CsNMAPK) was expressed in antisense orientation driven by the 35S promoter of cauliflower mosaic virus. The pBI-CsNMAPK plasmid DNA was introduced into cucumber embryo by the pollen-tube pathway method. All seeds were sown in the soil and screened for transformants with kanamycin, polymerase chain reaction (PCR), Northern blot and real-time quantitative reverse transcriptative PCR (RT-PCR) analysis. Two independent transgenic plants were obtained and analyzed. The results showed that the transgenic cucumber plants exhibited retarded growth. The transgenic plant height was shorter and the leaves were smaller. Transgenic cucumber plants suppression CsNMAPK were more sensitive to salt stress than the wild-type (WT) plants. The fresh weight of shoot of the transgenic plants decreased more than WT after 50 mM NaCl treatment for 7 days. The malondialdehyde (MDA) content was higher, while the superoxide dismutase (SOD) activity and proline accumulation were lower in the transgenic plants than the WT plants after NaCl stress treatment. The evidence indicated that CsNMAPK was involved in positive regulation of reactive oxygen species (ROS) scavengence and osmotic adjustment under salt stress.

Research highlights▶ Antisense CsNMAPK transgenic cucumber plants were obtained via the pollen-tube pathway. ▶ Antisense transgenic cucumber plants exhibited retarded growth. ▶ Antisense CsNMAPK plants have lower SOD activity than WT plants under NaCl treatment. Antisense CsNMAPK plants accumulated less proline than WT plants under NaCl treatment.