Two types of root nodule symbioses between nitrogen-fixing bacteria and plants are known. Rhizobia interact with legumes (Fabaceae) and Parasponia (Cannabaceae). Frankia actinobacteria enter symbioses with a diverse group of actinorhizal plants from eight families. All root nodule-forming plants go back to a common ancestor. Recent phylogenomic studies revealed that the ancestor was symbiotic, and subsequently, the symbiosis was lost in most lineages. In the lineages that retained the symbiosis, it was adapted. Nevertheless, some features are common to all root nodule symbioses. The genetic toolbox for plants to communicate with bacteria is shared with arbuscular mycorrhizal symbiosis.

In most types of root nodules, infected cells are arranged in a developmental gradient. In the senescence zone of legume nodules, papain-like cysteine proteinases (PLCPs) are formed and responsible for the breakdown of the intracellular microsymbionts. The same enzymes have been also implicated in the degradation of arbuscules, containing fungal intracellular microsymbionts. A nodule-specific PLCP, AgCP1, had been previously identified in the actinorhizal tree Alnus glutinosa. Homologs have been identified in other actinorhizal species. The goal of this study is to find out whether the regulation of nodule-specific PLCP expression is conserved in legumes and actinorhizal plants.

This project involves:

• Genome analysis
• RT-qPCR
• Preparation of promoter(mutant):reporter constructs using the GoldenGate technology
• Hairy root transformation of Lotus japonicus (legume) and Datisca glomerata (actinorhizal)

Contact

If interested, please contact:

Katharina Pawlowski:
katharina.pawlowski@su.se