Research Projects

Leguminous plants and soil-resident bacteria, known as rhizobia, form specialized organs called nodules on the root system. These nodules serve as an intracellular niche for atmospheric nitrogen fixation, beneficial to plants under nitrogen-limiting conditions. Nodule organogenesis is a post-embryonic developmental program characterized by de-differentiation and reactivation of specific groups of differentiated cells in the root system. In Dalbergioids legumes like Arachis hypogaea, a unique mode of infection by Bradyrhizobium spp through crack entry is observed. Following crack entry, Bradyrhizobium is internalized by root cells, triggering cell divisions in differentiated cortical cells through changes in phytohormones. This initiation requires a developmental reprogramming, leading to the formation of a nodule primordium containing a specialized group of cells within the infection zone called nodule meristem (NM). In Arachis, the NM remains active only during early stages of organogenesis, and the nodules are morphologically distinct from those with indeterminate nodule meristem. Recent studies have shown that root and nodule developmental pathways share several common meristem regulators, including the ortholog of Arabidopsis thaliana WUsCLE RELATED HOMEOBOX5 (WOX5). In Arachis hypogaea, AhWOX5 transcript was detected in the infection zone and abutting vascular bundles of the nodule primordium. However, the spatio-temporal expression pattern and role of AhWOX5 during determinate nodule meristem maintenance are currently unknown. This study aims to establish the role of AhWOX5 and cytokinin signaling cross talk in the context of determinate nodule organogenesis.