Genetic control of alkaloid production

Williams, W., Harrison, J. E. M. and Jayasekera, S. 1984. Genetic control of alkaloid production in Lupinus mutabilis on the effect of a mutant alle mutal isolated following chemical mutagenesis. Euphytica, 33 811-817. 

References for Chapter 2, Genetic Control of Alkaloid Production... 

Nevertheless, genetic engineering of a key enzyme in a chosen pathway does not always result in the enhancement of the end product thus, overexpression of pmt gene carried out in A. belladonna resulted in a 5-fold increased in pmt transcript level but an unchanged tropane alkaloid profile (hyoscyamine and scopolamine), as well as the tropane alkaloids biosynthetic precursors tropine, pseudotropine and tropinone which were not affected [134-135], Similarly, the overexpression of tobacco pmt gene in Dubosia hybrid hairy root cultures produced amounts of tropane alkaloid similar to control roots [131, 136]. All these results seem to indicate the presence of different points of control in the tropane alkaloid metabolic pathway. 

The biosynthetic pathways are universal in plants and are responsible for the occurrence of both primary metabolites (carbohydrates, proteins, etc.) and secondary metabolites (phenols, alkaloids, etc.). Secondary compounds were once regarded as simple waste products of a plant s metabolism. However, this argument is weakened by the existence of specialist enzymes, strict genetic controls and the high metabolic requirements of these componnds (Waterman and Mole 1994). Today most scientists accept that many of these componnds serve primarily to repel grazing animals or destrnctive pathogens (Cronquist 1988). 

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