Trifolin: a Rhizobium recognition protein from white clover

Area of Science:

• Plant-microbe interactions
• Molecular biology
• Biochemistry

Background:

• Symbiotic relationships between legumes and rhizobia are vital for nitrogen fixation.
• Plant lectins and agglutinins play roles in host recognition during symbiosis.
• Understanding clover-Rhizobium interactions is key to improving agricultural practices.

Purpose of the Study:

• To purify and characterize trifoliin, a protein from white clover.
• To investigate the role of trifoliin in the recognition of Rhizobium trifolii by clover roots.
• To elucidate the binding mechanism of trifoliin to Rhizobium trifolii.

Main Methods:

• Protein purification from white clover seeds and roots.
• Agglutination assays with Rhizobium trifolii.
• Antibody production and binding studies on clover seedlings.
• Elution studies using 2-deoxy-D-glucose.

Main Results:

• Trifoliin was purified and characterized as a protein with a Mr of approximately 50,000 and an isoelectric point of 7.3.
• Trifoliin specifically agglutinated Rhizobium trifolii at low concentrations and bound to encapsulated bacteria.
• Antibodies to trifoliin localized to clover root hairs, particularly at sites of bacterial binding, and did not bind to other legume roots.
• 2-Deoxy-D-glucose eluted trifoliin, indicating carbohydrate-mediated binding to root cell walls.

Conclusions:

• Trifoliin is a key component of white clover involved in the specific recognition of Rhizobium trifolii.
• The carbohydrate-binding properties of trifoliin are essential for its anchoring to clover root cell walls.
• Trifoliin likely mediates the initial interaction between clover and its symbiotic partner, Rhizobium trifolii.