Effects of spermine and spermi¬dine on cell division and wall morphogenesis in Saccharomyces cerevisiae

The effect of polyamines (PA) on the synthesis and deposition of wall constituents in Saccharomyces cerevisiae was investigated. Spermidine (Spd) in various doses was ineffective whereas spermine (Sp) in the same concentrations caused a marked inhibition (25-60%) of cell proliferation accompanied by evident morphogenetic malformations. Sp-treated cells were elongated, grouped in small clusters, and showed malformed septa and aberrant wall thickenings. The PATAg technique revealed that the aberrations consisted of an abnormal accumulation of both reactive materials, like 1,3-beta-glucans, and unstained chitin components. Since 1,3-beta-glucan synthases and chitin synthases are inserted in the plasma membrane, whose anionic sites interacted with the cation groups of Sp, it is assumed that the molecule determines a condition resulting in an unregulated activation of the two enzymes. The fact that Spd, which contains three cationic groups instead of the four contained in Sp, is without effect suggests that a compound must have at least four cation sites in order to affect the cell division and wall morphogenesis of S. cerevisiae.