title: Effect of various inhibitors of polyamine synthesis on the growth of Helianthus tuberosus.
abstract: The growth effect of various inhibitors of polyamine synthesis was studied on explants obtained from Helianthus tuberosus tubers during dormancy and dormancy break and cultured for 20 days on a sterile agarized medium. Explant growth was strongly inhibited by canavanine and canaline, natural non-protein amino acid analogues of arginine and ornithine, respectively, as well as by canavanine in combination with putrescine. Methylglyoxal-bis-guanylhydrazone, an inhibitor of S-adenosylmethionine decarboxylase, did not increase growth inhibition caused by canavanine. Methylglyoxal-bis-guanylhydrazone alone, as well as alpha-methylornithine, 1,3-diaminopropane and 1,3-diaminopropan-2-o1 - which are inhibitors of ornithine decarboxylase - showed no growth inhibition with respect to the control treated with 2,4-dichlorophenoxyacetic acid. 1,3-Diaminopropane caused a paradoxic enhancement of callus growth and a much greater polyamine accumulation than in the control with 2,4-dichlorophenoxyacetic acid alone. During the first cell cycle inactivated tuber slices, 40 microM methylglyoxal-bis-guanylhydrazone inhibited spermidine and spermine synthesis up to 6 h, and their accumulation up to 1 h; RNA synthesis and accumulation and DNA accumulation were reduced at 1 h, and later enhanced. During the same period, 1 mM canavanine inhibited putrescine synthesis in the S and M phases, and spermidine and spermine synthesis only at 24 h; accumulation of putrescine and spermidine was reduced only at 12 h. Canavanine also reduced RNA synthesis throughout the S and M phases, while RNA accumulation was reduced at 18 and 24 h. Two different hypotheses are put forward concerning the induction of new pathways of polyamine synthesis.
mesh_terms: D012437:Adenosylmethionine Decarboxylase / Q000037:antagonists & inhibitors; D002172:Canavanine / Q000494:pharmacology; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors; D002453:Cell Cycle; D006368:Helianthus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D008935:Mitoguazone / Q000494:pharmacology; D009696:Nucleic Acids / Q000378:metabolism; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines / Q000096:biosynthesis*
chemical_list: D009696:Nucleic Acids; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; D002172:Canavanine; D002262:Carboxy-Lyases; C019722:arginine decarboxylase; D012437:Adenosylmethionine Decarboxylase; D008935:Mitoguazone