Cytoskeleton-induced Alterations of Lectin Activity in Modification of the Calcium Signaling System

The roots of 7-d seedlings of two winter wheat cultivars differing in frost resistance were used to study changes in lectin activity using the inhibitor of microtubule polymerization oryzalin (15 μM) in unhardened (23oC) and hardened (2–3oC, 3–7 d) plants. Plants were grown with the antagonist of calmodulin, chlorpromazine (250 μM) or without chlorpromazine in medium. It was shown that the dynamic of lectin activity during cold hardening differed in two culrivars investigted. Disruption of the calcium signaling chain using chlorpromazine eliminates these differences in lectin activity. As a result we observed the same alterations in the activity of cell wall lectins. Pretreatment of plants with oryzalin increased the activity of cell wall lectins and decreased the activity of soluble lectins. It is supposed that an interaction exists between lectins of cell wall and microtubules. Plant cold hardening decreased the oryzalin effect on the lectin activity. These results could be explained by the appearance of tolerant microtubules with less affinity to the inhibitor. As with oryzalin, chlorpromazine decreased the activity of soluble lectins and increased the activity of cell wall lectins but to a greater degree. Apparently, injury of microtubule phosphorylation results in a more considerable microtubule disorganization than that observed after oryzalin effects. However, in cold hardened plants of Albidum 114, chlorpromazine promoted the oryzalin effect on lectin activity. It is possible that injury of Ca2+-signaling system blocks the appearance of tolerant microtubules during cold hardening. Therefore, functioning of the Ca2+-signaling system is necessary for microtubule stabilization. It is concluded that the activity of cell wall lectins depends on microtubule status which is regulated by the calcium signaling system.