Polyamines and Morphogenesis - Effects of Methylglyoxal-bis(guanylhydrazone)

The effects of methylglyoxal-bis(guanylhydrazone) (MGBG), an inhibitor of polyamine biosynthesis were studied on tuberization and cellular polyamine content using in vitro Solanum tuberosum (cv Binjte) plants. When MGBG was added to the culture medium, it produced a partial inhibition of the growth of stems and leaves; it totally blocked rhizogenesis and strongly stimulated tuber formation. Morphogenetic effects of MGBG were correlated to a 40 % decrease in free putrescine, spermidine, spermine content of the leaves and to a 28 % decrease in spermidine titer of the stems. In the tubers, this inhibitor did not change the free polyamine titer but increased by up to 85 % the titer of conjugated putrescine, spermidine, spermine. When the plants were grown in the dark, MGBG produced, like benzyladenine, a stimulation of the rate of tuberization and enhanced the content of conjugated polyamines in the tuber. These results support the hypothesis that polyamines play an important role in the morphogenesis of potato plants. The role of polyamine conjugation in tuber development is discussed.