Research Projects

Mitogen-activated protein kinases (MAPKs) are ubiquitously present kinases in eukaryotes and are known to regulate the cellular homeostasis of a plant pertaining to a variety of stimuli. They are involved in a variety of signal transduction pathways operating in abiotic and biotic stresses, and developmental processes. However, there is no report that suggests a direct role of MAPKs in regulating photosynthesis. Based on the preliminary results obtained in PI’s laboratory, the present proposal is devised to elucidate the regulation of photosynthesis by MAPKs. We observed that the rice transgenic over-expressing two of the important members of the MAPK gene family namely, OsMPK3 and OsMPK6 under the control of inducible promoter exhibit a significant change in net photosynthesis rate and related parameters compared to its wild-type relatives. Moreover, the transcript accumulation of photosynthesis-related genes was also found to be differentially regulated in MPK3 and MPK6 OE lines. One such gene is ACTPK1, a member of the family of dual specificity kinases in rice whose homologues are reported to have a role in chloroplast differentiation and photosynthetic activity regulation in Arabidopsis. In silico data and preliminary transcript expression results suggest that this family is regulated by light, hinting towards its possible role in photosynthetic processes and are potential substrates of rice MAPKs. Since MAPKs are known to be confined to the nucleus and cytoplasm, we hypothesize that ACTPK1 could be a phosphorylation target of OsMPK3 and/or OsMPK6. The MAPK-mediated phosphorylation of ACTPK1 subsequently regulates the transit-peptides of nuclear-encoded photosynthesis related protein for targeting them to the chloroplast. We propose to generate at least four transgenics related to ACTPK1 in rice to elucidate the underlying mechanism of action of ACTPK1 in regulating photosynthesis. First, we will develop knock-out mutants and over-expressing lines of ACTPK1 in rice. After establishing the interaction and phosphorylation of MAPK, we will over-express phosphor-mimetic and phosphor-dead versions of ACTPK1 in the background of actpk1 knock-out mutant rice lines under the control of its native promoter. The study will elucidate the fundamental knowledge of regulation photosynthesis by versatile MAPK cascade by regulating ACTPK1 that may have its application in improving the rice yield.