Arsenic stress activates MAP kinase in rice roots and leaves.

The toxic metalloid arsenite has become a potential threat to rice growing regions leading to serious contamination in food chain. In the present study effect of different physiological concentration of arsenite that is toxic and triggers the molecular events were evaluated in rice seedlings. Along with severe effect on the growth of rice seedling, production of reactive oxygen species (ROS) and nitric oxide (NO) in arsenite treated rice roots was also observed. Activation of a 42kDa mitogen activated protein kinase (MAPK/MPK) by arsenite was observed in rice leaves and 42 and 44kDa in roots in dose dependent manner. The activated MAPK could be immunoprecipitated with anti-phospho-tyrosine antibody, 4G10. The kinetic of MAPK activation by arsenite was found to be dose dependent. Transcript analysis of MAPK family and immunokinase assay in arsenite treated rice seedling revealed significant level of induction in OsMPK3 transcripts in leaves and OsMPK3, OsMPK4 transcripts in roots. Among MAPK kinase (MKKs) gene family, OsMKK4 transcripts were found to be induced in arsenite treated rice leaves and roots. In-silico homology modeling and docking analysis supported OsMPK3-OsMKK4 interaction. The data indicates that arsenite stress is transduced through MAPK signaling cascade in rice.