Repeating particles associated with membranes of transfer cells

Area of Science:

• Plant biology
• Cell biology
• Microbiology

Background:

• Root nodules in legumes like Trifolium repens are crucial for symbiotic nitrogen fixation.
• Transfer cells play a vital role in nutrient exchange between the plant and bacteria.
• Understanding the membrane structure of these cells is key to elucidating symbiotic efficiency.

Purpose of the Study:

• To investigate the ultrastructure of unfixed root nodule transfer cells in Trifolium repens.
• To identify and characterize particle arrangements on the plasmalemma and bacteroid membranes.
• To provide structural insights into the symbiotic interface.

Main Methods:

• Freeze etching technique applied to unfixed root nodule tissues.
• Transmission electron microscopy for visualizing membrane structures.
• Analysis of particle distribution and lattice arrangement.

Main Results:

• Regular arrays of 11 nm particles were observed on the plasmalemma of transfer cells.
• These particles formed a hexagonal lattice with 15 nm spacing, associated with wall ingrowths.
• Smaller, similarly arranged particles were also found on bacteroid membrane envelopes.

Conclusions:

• The observed particle arrays suggest specialized membrane domains in Trifolium repens transfer cells.
• These structures may be involved in nutrient transport or signaling during symbiosis.
• The findings highlight the structural organization of membranes at the plant-microbe interface.