Molecular cloning and characterization of a partial mitogen-activated protein kinase cDNA, CnMAPK1 induced in response to water stress in coconut

Plants have developed a fine-tuned complex of stress responses, among which one of the earliest signaling pathways after perception of stimuli is the evolutionary conserved mitogen-activated protein kinase (MAPK) cascade. These cascades are major pathways by which extracellular signals are transduced into internal responses. In this study, oligonucleotide primers were designed based on conserved regions of plant MAPK sequences available in pubic databases. A cDNA clone of 467 bp encoding a MAPK (designated CnMAPK1) was isolated by RT-PCR from leaves of coconut plantlets subjected to water stress using polyethylene glycol (PEG) treatment. CnMAPK1 was significantly homologous to other plant MAPKs viz., MPK7 and MPK5 from Zea mays, SIPK and MAPK6 from Oryza sativa and FLRS from Triticum aestivum (93% identity). Coconut MAPK belongs to the Serine/Threonine Kinases (STKs), Plant TEY MAPK subfamily group A. Molecular modeling of the coconut MAPK was also undertaken.