Alkaloids, genetics

In fhe early 1980s, root cultures of Nicotiana, Hyoscyamus, Datura and Duboisia species were found fo give high yields of nicotine and tropane alkaloids and have proved useful fools for recent studies of the biosynthetic pathways to these alkaloids. Genetically transformed and untransformed root cultures have been generated and used as models for biosynthetic studies (Rhodes et al, 1990 Robins et al, 1994a,b Wildi and Wink, 2002). 

Sawaya AHE, Vaz BG, Eberlin MN, Mazzafera P (2011) Screening species of Pilocarpus (Rutaceae) as sources of pilocarpine and other imidazole alkaloids. Genet Resour Crop Evol 58 471 80. doi 10.1007/s 10722-011-9660-2... 

Most alkaloid genetics research has been performed on interspecific crosses. There are some disadvantages of such studies. While the parent plants are fertile and viable, the hybrid is usually sterile, and the development of most plants is abnormal however, occasional hybrids are viable and vigorous. Seeds are produced in some instances, but the ratio of developed seeds to the number of ovules produced is very low. Also, only a small percentage of the pollen grains is viable. To secure the large number... 

Although low levels of methylxanthines have been detected in the leaves and flowers of T. cacao, the primary storage location is within the seed or bean.16 The cocoa bean is the major natural source of the methylxanthine theobromine, but contains only small amounts of caffeine. Theophylline has been detected in cacao beans, but at such low concentrations that its presence generally is ignored. Together, theobromine and caffeine account for up to 99% of the alkaloid content of T. cacao beans. Alkaloid content is affected by genetic makeup, maturity of beans at harvest, and fermentation process. Analytical methodology also is partially responsible for some of the disparity in methylxanthine values since many early methods were unable to separate theobromine and caffeine. 

Since 1988, the methods that we use to isolate cDNAs of alkaloid biosynthesis have become ever more facile and sensitive, allowing for more efficient cDNA identification. We do not, however, yet understand enough about the cellular localization of alkaloid formation or about the nature of the catalysts to move completely away from enzymology and biochemistry and to use only molecular genetic techniques to dissect these biosynthetic pathways. Even our most recently successful cDNA isolations and identifications involved classical protein purification. We are beginning now to use proteomics and EST sequencing to identify natural product biosynthetic cDNAs, but these approaches are more feasible when a specialized cell/tissue type in which secondary metabolite biosynthetic pathways are active, can be isolated and used as a protein or RNA source. 

Yang described the Pd-induced cyclization of an aryl bromide onto a pendant cyano group leading to y-carbolines and related compounds [488], Genet studied the use of chiral palladium complexes in the construction of the C-ring of ergot alkaloids, a study that culminated in a synthesis of (-)-chanoclavine I [489-491]. For example, nitroindole 388 is cyclized to 389 in 57% yield and with enantioselectivities of up to 95% using Pd(OAc)2 and (S)-(-)-BINAP. 

We were forced to review our interpretation of the corematal message. HD, it seemed, could serve not only for proclamation of alkaloid load and of a genetic capacity, but for advertisement of a nuptial gift. We postulated that the magnitude of the male s PA offering should be proportional to his PA load, and we found this to be the case (24). 

T. rufonigra from India and T penzigu T. clypeata and T. sp. cf. emeryU all three from Africa, had no tetraponerines. Surprisingly, the extract from another collection of T. allaborans was also devoid of alkaloids. Thus, the presence or absence of tetraponerine alkaloids cannot be considered a taxonomic marker for the genus until the genetic or environmental factors responsible for their production are uncovered and understood [131]. 

Hashimoto T, Yun D-J, Yamada Y. (1993) Production of tropane alkaloids in genetically engineered root cultures. Phytochemistry 32 713-718. 

Daly, J. W., Secunda, S. I., Garaffo, H. M., et al. (1992). Variability in alkaloid profiles in neotropical poison frogs (Dendrobatidae) genetic versus environmental determinants. Toxicon 30,887-898. 

Easton HS et al., Ryegrass host genetic control of concentrations of endophyte-derived alkaloids. Crop Sci 42 51-57, 2002. 

Spiering MJ et al.. Expressed sequence tags and genes associated with lofine alkaloid expression by the fungal endophyte Neotyphodium uncinatum. Fungal Genet Biol 5G.2A2—2 yli, 2002. 

Spiering MJ et al. Gene clusters for insecticidal loline alkaloids in the grass-endophytic fungus Neotyphodium uncinatum, Genetics 169 1403—1414, 2005. 

Although L-phenylalanine is a protein amino acid, and is known as a protein acid type of alkaloid precursor, its real role in biosynthesis (providing C and N atoms) only relates to carbon atoms. L-phenylalanine is a part of magic 20 (a term deployed by Crick in his discussion of the genetic code) and just for this reason should also be listed as a protein amino acid type of alkaloid precursor, although its duty in alkaloid synthesis is not the same as other protein amino acids. However, in relation to magic 20 it is necessary to observe that only part of these amino acids are well-known alkaloid precursors. They are formed from only two amino acid families Histidine and Aromatic and the Aspartate family . 

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