Executive Summary : | Nitrogen is a crucial element for proper growth and development of plants which considerably enhances the yield in the field. Plants consume nitrogen (N) in the form of ammonium (NH4) and nitrates (NO3); therefore, farmers maintain soil fertility by using nitrogen manures to enhance crop yield. To circumvent the adverse effects of excessive use of fertilizers on the environment, BNF (biological nitrogen fixation) is a powerful approach for modern agricultural perspectives. For example, soil bacteria rhizobia can contribute at least 70 million tonnes of nitrogen per year by forming symbiotic relationship with leguminous plants. Rhizobia form a mutualistic association with legumes by establishing a specialized organ called root nodules. Within nodules, rhizobia fix nitrogen from the atmosphere for the host plants, and in turn, the plant furnishes other nutrients to the bacteria thus, building a symbiotic association. Increased plant yield and reduced depletion of soil nitrogen would be possible by enhancing root nodule symbiosis (RNS) in legumes. Peanut is one of the major oil seed legumes in India and therefore, improvement in root nodulation in peanut could be one of the suitable ways to increase its productivity in farming land. NIN (Nodule inception) gene is a central modulator of symbiosis signaling as it regulates rhizobial entry, development of the root nodule and autoregulation of nodulation. There is extensive knowledge of NIN-mediated signaling in the infection thread model prevalent in Medicago truncatula and Lotus japonicus. However, NIN dependent regulation of RNS involved in crack entry model in peanut (Arachis hypogeae) is largely unknown. Functional characterization of multiple NIN genes will decipher how NIN-mediated signaling cascades monitor genetic networks necessitating root nodulation in allopolyploid peanut. Identification and comprehensive analysis of NIN targeted genes in response to rhizobial infection will enhance our understanding, in the broader context, of how NIN-mediated signaling mechanisms fine-tune downstream components and its cross-talk with other signaling networks. Further functional analysis of downstream components will divulge a NIN- dependent fundamental molecular mechanisms of nodule formation in peanut and probably other legumes. These evidences may have long-term implications for a better understanding of the interaction between rhizobia and peanut. The knowledge gained from this research will be beneficial for breeding and engineering traits to develop nitrogen-rich plants, which is currently one of the major challenges for sustainable agriculture. In addition, my extensive research experience on heterotrimeric G-protein-mediated root nodule symbiosis using genetic, biochemical, and molecular approaches will be helpful to efficiently address this proposal's overall objectives. |