ANNOUNCEMENTS
Rice (Oryza sativa) is the second most widely grown cereal and staple food worldwide. It is a primary source of energy but heavily relies on synthetic fertilizers, has low nitrogen use efficiency and harms the environment. In contrast, legumes possess the unique ability to establish root nodule symbiosis (RNS) with rhizobia, which allows them to fix biological nitrogen. Transferring this capability to rice represents a promising strategy for sustainable agriculture. This thesis investigates whether rice can perceive rhizobial NFs and determine if the nod signal is appropriately communicated via CSSP in the roots and transmission of the nod signal in the root cell by the introduction of key legume-derived Nod factor (NF) receptors and nodulation transcription factors (TFs) genes. Legume-specific NF receptor genes (MtNFP and MtLYK3), along with supporting signaling components (MtDMI2, LjLNP, and MtSYMREM1) and nodulation-related TFs MtNSP1, MtNSP2, MtERN1, and MtNIN , were introduced into rice via biolistic transformation. Transgenic rice lines were molecularly characterized to confirm stable integration and expression of the transgenes.
The studies revealed that transgenic rice plants perceive NF exhibiting early symbiotic responses upon treatment with NF or inoculation with S. meliloti. These responses included significant root hair deformation, surface colonization, and activation of Ca²⁺ fluxes and oscillations/ spiking. Expression of symbiosis-related genes was also upregulated in transgenic roots, indicating successful transmission of Nod factor signals through the rice symbiotic signaling network. This work provides a foundational step toward developing nitrogen-fixing cereal crops and reducing dependence on synthetic nitrogen fertilizers.
