The role of tubulin transport between the nucleus and the cytoplasm

Tubulin is the basic building block of microtubules which ensure intracellular transport, morphological changes, the connection of proteins of metabolic pathways, the segregation of chromosomes during mitosis and many other essential processes in plant cells. The localization of tubulin regarding nucleus is strictly controlled and during the interphase, tubulin is usually not present in the nucleus. As we previously showed, one of the exceptions of the presence of tubulin in the nucleus is the cold stress condition. Also, we discovered several plant-specific nuclear export sequences (NES) in tubulin molecules: one in α-tubulin and two in β-tubulin. In this work I found that double mutation of both functional β-tubulin NESes cause slight accumulation of the protein in the nuclei. However, the phenotype of the transgenic plants expressing β-tubulin with mutations is probably not affected by the presence of the mutated protein. The effect of the expression of the mutated β-tubulins was observed in Nicotiana tabacum BY-2 cells as well. The expression of β-tubulin carrying a single NES3 mutation or double mutation of both NESes bring changes of the division activity of the cells, while the NES2 mutation does not have any effect. Furthermore, it was discovered that the 0řC cold tr eatment does not cause..