Abstract

The mitogen activated protein kinase (MAPK/MPK) cascade is known to regulate several stress responses and developmental processes in eukaryotes. The cascade usually consists of three tier component comprising of MAPK , MAPK kinase (MAPKK/ MAP2K / MKK) and MAPKK kinase (MAPKKK/ MAP3K / MKKK). All these three components are connected to each other by an event of phosphorylation. Upon activation MAPK phosphorylates various cytosolic and nuclear proteins for appropriate cellular readjustment. The role of this cascade will be discussed in light signal transduction pathway during seedling development in Arabidopsis and submergence tolerance in rice. In Arabidopsis the activation and interaction of AtMPK6 with MYC2 transcription factor was observed to be blue light (BL) dependent. AtMKK3 was identified as an upstream kinase of AtMPK6 in the same pathway. The role of MYC2 has been deciphered as a negative regulator of blue light signaling in Arabidopsis. In rice we identified regulation of SUB1A1 specifically by OsMPK3. SUB1AI is one of the genes of SUBMERGENCE1 (SUB1) quantitative trait locus that confers submergence tolerance up to two weeks in certain varieties of rice. SUB1A1 was identified as an interacting partner as well as phosphorylation target of OsMPK3 in a submergence dependent manner. We propose a positive feedback loop that governs SUB1A1 interaction with MPK3 and impacts on submergence tolerance in rice.