Inducible alkaloid biosynthesis

The production of toxins is only one aspect of plant defense strategy. As a result of the persistent battle of plants and herbivores, many optimized phenotypes have evolved, such as the preferential accumulation of alkaloids in tissues with a pattern that is consistent with predictions of optimal defense theory,65 i.e., the defense metabolites are allocated preferentially to tissues with a high probability of attack.66 The inducibility of pathways leading to plant secondary compounds as a strategy to minimize the costs of plant defense is a result of permanent optimization. One of a few examples of inducible alkaloid biosynthesis is the different Nicotiana species that exhibit dramatic wound-induced increases of nicotine, nomicotine, or anabasine.67... 

PAULI, H.H., KUTCHAN, T.M., Molecular cloning and functional heterologous expression of two alleles encoding (5)-Y-methylcoclaurine 3 -hydroxylase (CYP80B1), a new methyl jasmonate-inducible cytochrome P-450-dependent monooxygenase of benzylisoquinoline alkaloid biosynthesis, Plant J., 1998,13, 793-801. 

SCHRODER, G., UNTERBUSCH, E KALTENBACH, M SCHMIDT, J., STRACK, D., DE LUCA, V., SCHRODER, J., Light induced cytochrome P450-dependent enzyme in indole alkaloid biosynthesis tabersonine 16 hydroxylase., FEBSLett., 1999,458,97-102. 

Schroeder, G., E. Unterbusch, M. Kaltenbach, J. Schmidt, D. Strack, V. De Luca et al. (1999). Light-induced cytochrome P450-dependent enzyme in indole alkaloid biosynthesis Tabersonine 6-hydroxylase. FEBS Lett. 458, 97-102. 

Besides the induction of some of the steps of indole alkaloid biosynthesis, it was found that the enzyme isochorismate synthase was also induced by fungal elicitors (e.g., P. aphanidermatum), at the same time 2,3-dihydroxybenzoic acid (DHBA) was produced (151,163,339). 5-Chloro-sali-cylic acid and 2,6-dichloro-isonicotinic acid enhanced the elicitor effect in... 

The alkaloid biosynthesis is thus not expressed in the cell suspension cultures. However, another secondary metabolite pathway is operative. The yellow-orange coloured products formed by the cell cultures were identified as anthraquinones, at that time not yet known as product from Cinchona trees. Further studies proved that these compounds probably acts as phytoalexins in Cinchona (37). They have antimicrobial activity, their production can be induced by microrganisms (e.g. fungi) and preparations thereof. Also in infected Cinchona trees we have been able to proof the presence of anthraquinones, whereas healthy ones are free of these compounds (38). 

Salim V, Yu F, Altarejos J, DeLuca V (2013) Virus-induced gene silencing identifies Catharanthus roseus 7-deoxyloganic acid-7-hydroxylase, a step in iridoid and monterpene indole alkaloid biosynthesis. Plant J 76 754-765... 

Enzymes of alkaloid biosynthesis are induced in a coordinated manner by an internal signal during development of the mold. However, the rates of alkaloid production increase later than enzyme activities, The increase of both processes can be stopped by addition of inhibitors of gene expression, e.g., 6-fluorouracil or cycloheximide (cf. arrows), indicating that alkaloid production is controlled by the formation of a protein which is not an enzyme of alkaloid biosynthesis. Ordinate relative values A A anthranilic acid adenylyl transferase (a) CD cyclopeptine dehydrogenase (v) DE dehydrocyclopeptine epoxidase ( ) CmH cyclopenin m-hydroxvlase (A)... 

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