Genetic factors regulating cluster roots of white lupin

• Applicant: Professor Dr. Uwe Ludewig
• Subject Area: Plant Cultivation, Plant Nutrition, Agricultural Technology ; Plant Genetics and Genomics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 413902939

Phosphorus is a globally limited, essential macroelement for plant growth, but its bioavailability in soil is typically low. The legume white lupin (Lupinus albus) has an outstanding ability to mobilize and acquire sparingly soluble soil orthophosphates (Pi) under phosphate-deficient conditions. Special brush-like root structures, so-called cluster roots, which develop under iron- and phosphate-deficiency, serve for this purpose. Cluster roots are also found in some wild plants that are best adapted to highly P impoverished soils. The initiation of clusters relies on the dense positioning of lateral root primordia behind the root tips of first order laterals. Shortly after the initiation and outgrowth of densely root-hair-covered rootlets, their meristems die in a coordinated manner to restrict their length. The cluster rootlets finally release high amounts of P-solubilizing organic anions, which liberate soil Pi for subsequent uptake. Systemic, metabolic and phytohormonal signals involved in cluster root formation resemble factors that are involved in lateral root formation in other plants, but essential genetic factors for clusters are still unknown. In some model plants and several legumes, the lateral rooting is also regulated by small, processed peptides and their receptors. Furthermore, similar receptors regulate nodule density in legumes. Most interestingly, first data suggest that one peptide is involved in cluster root formation. As a consequence, peptides and their receptors may be the missing link to understand cluster root formation. We will isolate small peptides from native clusters and screen candidate peptides for their effects on clusters. The "hairy-root" transformation method for white lupin is chosen to further test the importance of a certain receptor / peptide pair. The proposed work may identify necessary genetic factors for the formation of cluster roots. Underlying genes are not only of great scientific interest to understand a peculiar characteristic in specialist plant species, but also might enable long-term transfer of the cluster root trait to other crop species.

• DFG Programme: Research Grants