Activity of Lectin-Like Proteins of the Cell Walls and the Outer Organelle Membranes as Related to Endogenous Ligands in Cold-Adapted Seedlings of Winter Wheat

The hemagglutinating activity (HA) of lectin-like components in the cell walls and the outer organelle membranes was studied in freezing-tolerant winter wheat (Triticum aestivum L., cv. Mironovskaya 808) plants in the course of hardening at 2°C, in parallel with the effects of endogenous ligands from the soluble fraction on HA. Low hardening temperature divergently changed HA of the lectin-like components in the cell walls, the outer membranes of nuclei, plastids, and mitochondria, and the microsomal membranes: HA increased in the cell walls, nuclei, and plastids and decreased in the mitochondria and microsomal membranes. Under hardening conditions, with plant growth slowed down, HA of the lectin-like proteins from the outer organelle membranes was inhibited in the presence of the soluble fraction components (soluble ligands); such inhibition was not observed in the case of actively growing nonhardened seedlings. The authors put forward a hypothesis that the lectin-like proteins from both peripheral (cell walls) and intracellular (outer organelle membranes) compartments are essential for developing freezing tolerance. HA of the cell walls and the outer membranes of nuclei and plastids enhanced by hardening manifested positive correlation with freezing tolerance and negative correlation with the growth rate. In contrast, HA of the outer membranes of mitochondria and microsomes was positively related to plant growth and negatively, to freezing tolerance. As negative and positive effectors of membrane-dependent processes, the lectin-like components of the outer organelle membranes seem to control membrane functional activities in the course of cold adaptation.