EFFECT OF THE ROL GENES FROM AGROBACTERIUM-RHIZOGENES ON POLYAMINE METABOLISM IN TOBACCO ROOTS

Using tobacco root cultures, we explored the possibility of a correlat ion between the expression of the rol genes from the TL-DNA (rolA, rol B, rolC) of Agrobacterium rhizogenes and changes in polyamine content and metabolism. Transgenic roots were induced by inoculation of Nicoti ana tabacum cv. Xanthi leaf discs with a disarmed strain of A. tumefac iens harbouring the rolA, rolB and rolC genes either singly or in comb ination; the presence of these genes on the plant genome was confirmed by Southern blot analysis. Transgenic roots, especially those transfo rmed either by a combination of the three rol genes (A+B+C) or the rol C alone, grew faster than the untransformed roots. Putrescine, spermid ine and traces of spermine were present in all samples, both in free a nd bound forms. While rolA roots showed increased levels of free and b ound polyamines as compared with controls, accumulation of polyamines in rolB and rolC roots was inhibited or maintained, with the exception of a 66 and 48% increase, respectively, in the PCA-soluble conjugated fraction. In roots transgenic for all three rol genes (A+B+C), the po lyamine content remained almost unaltered compared with controls, sugg esting that rolB and rolC genes could nullify or compensate the rolA e ffects. The higher polyamine contents found in roots transformed by ro lA paralleled with higher ornithine (EC 4.1.1.17) and arginine (EC 4.1 .1.19) decarboxylase activities as well as higher nicotine production. It is suggested that polyamine metabolism in root cultures is altered by expression of rol genes.