Increasingly, as a result of recent biochemical work, there exists a realistic possibility of taking a molecular genetic approach to the manipulation of alkaloid-producing pathways in plant tissue cultures. In the pathways forming indole alkaloids in CATHARANTHUS ROSEUS, tropane alkaloids in DATURA and HYOSCYAMUS species, and nicotine in NICOTIANA species, recent studies have identified a number of key enzymes and at least some of the factors that regulate their levels of activity. Such knowledge contributes the basis upon which it has become feasible to design a strategy by which the flux in these pathways may be enhanced at the genomic level. This review presents a summary of the state-of-the-art pertaining to these pathways and discusses the strategy to be adopted for a molecular approach to their manipulation, together with some of the pitfalls that may arise when trying to alter their natural regulation.

10.1055/s-2006-960226

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Citations (22)

The Effects of Over-Expressing the Yeast Ornithine Decarboxylase Gene upon the Nicotine and Polyamine Levels in Transformed Roots of Nicotiana Rustica

Current plant science and biotechnology in agriculture (1990)

John D. Hamill Richard J. Robins A. J. Parr David M. Evans Judith M. Furze

Arginine decarboxylase

Polyamine

Ornithine decarboxylase antizyme

10.1007/978-94-009-2103-0_110

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Citations (4)

Manipulating secondary metabolism in culture

Springer eBooks (1993)

John D. Hamill Michael Rhodes

Phytochemical

Plant metabolism

Secondary metabolism

10.1007/978-94-011-2142-2_5

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Citations (102)

Metabolic consequences of knocking outUGT85B1, the gene encoding the glucosyltransferase required for synthesis of dhurrin inSorghum bicolor(L. Moench)

Plant and Cell Physiology (2015)

Cecilia K. Blomstedt Natalie H. O’Donnell Nanna Bjarnholt Alan Neale John D. Hamill

Many important food crops produce cyanogenic glucosides as natural defense compounds to protect against herbivory or pathogen attack. It has also been suggested that these nitrogen-based secondary metabolites act as storage reserves of nitrogen. In sorghum, three key genes, CYP79A1 , CYP71E1 and UGT85B1 , encode two Cytochrome P450s and a glycosyltransferase, respectively, the enzymes essential for synthesis of the cyanogenic glucoside dhurrin. Here, we report the use of targeted induced local lesions in genomes (TILLING) to identify a line with a mutation resulting in a premature stop codon in the N-terminal region of UGT85B1 . Plants homozygous for this mutation do not produce dhurrin and are designated tcd2 ( totally cyanide deficient 2 ) mutants. They have reduced vigor, being dwarfed, with poor root development and low fertility. Analysis using liquid chromatography–mass spectrometry (LC-MS) shows that tcd2 mutants accumulate numerous dhurrin pathway-derived metabolites, some of which are similar to those observed in transgenic Arabidopsis expressing the CYP79A1 and CYP71E1 genes. Our results demonstrate that UGT85B1 is essential for formation of dhurrin in sorghum with no co-expressed endogenous UDP-glucosyltransferases able to replace it. The tcd2 mutant suffers from self-intoxication because sorghum does not have a feedback mechanism to inhibit the initial steps of dhurrin biosynthesis when the glucosyltransferase activity required to complete the synthesis of dhurrin is lacking. The LC-MS analyses also revealed the presence of metabolites in the tcd2 mutant which have been suggested to be derived from dhurrin via endogenous pathways for nitrogen recovery, thus indicating which enzymes may be involved in such pathways.

Glucosyltransferases

TILLING

Vitaceae

10.1093/pcp/pcv153

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Citations (34)

Co-Culture of Hairy Roots and Shooty Teratomas

CRC Press eBooks (2020)

Muhammad Ahkam Subroto M.G.P. Mahagamasekera Kian H. Kwok John D. Hamill Pauline M. Doran

Hairy roots have been demonstrated to have great potential for production of plant secondary metabolites. This characteristic gives hairy roots an important intrinsic advantage compared with dedifferentiated tissues by overcoming problems with low yields of secondary metabolites in callus and suspension cultures. Thus, root-shoot co-culture becomes possible using hairy roots and their genetically transformed shoot counterparts, 'shooty teratomas'. Genetically transformed shooty teratomas are produced by infection of plant material with Agrobacterium tumefaciens. Like hairy roots, shooty teratomas display a wide range of morphologies as described by M. A. Subroto et al. The success of co-culture using transformed organs from different plant genera shows that, provided the roots and shoots require similar nutrients and culture conditions and do not secrete inhibitory by-products into the medium, biotransformations which do not normally occur in vivo could be carried out in vitro with the potential for commercial exploitation.

10.1201/9780367810610-7

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Citations (4)

Effects of PEG-induced osmotic stress on growth and dhurrin levels of forage sorghum

Plant Physiology and Biochemistry (2013)

Natalie H. O’Donnell Birger Lindberg Møller Alan Neale John D. Hamill Cecilia K. Blomstedt

10.1016/j.plaphy.2013.09.001

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Citations (74)

Desiccation-tolerance specific gene expression in leaf tissue of the resurrection plant Sporobolus stapfianus

Functional Plant Biology (2007)

Tuan Ngoc Le Cecilia K. Blomstedt Jianbo Kuang Jennifer R. Tenlen D. F. Gaff

The desiccation tolerant grass Sporobolus stapfianus Gandoger can modulate cellular processes to prevent the imposition of irreversible damage to cellular components by water deficit. The cellular processes conferring this ability are rapidly attenuated by increased water availability. This resurrection plant can quickly restore normal metabolism. Even after loss of more than 95% of its total water content, full rehydration and growth resumption can occur within 24 h. To study the molecular mechanisms of desiccation tolerance in S. stapfianus, a cDNA library constructed from dehydration-stressed leaf tissue, was differentially screened in a manner designed to identify genes with an adaptive role in desiccation tolerance. Further characterisation of four of the genes isolated revealed they are strongly up-regulated by severe dehydration stress and only in desiccation-tolerant tissue, with three of these genes not being expressed at detectable levels in hydrated or dehydrating desiccation-sensitive tissue. The nature of the putative proteins encoded by these genes are suggestive of molecular processes associated with protecting the plant against damage caused by desiccation and include a novel LEA-like protein, and a pore-like protein that may play an important role in peroxisome function during drought stress. A third gene product has similarity to a nuclear-localised protein implicated in chromatin remodelling. In addition, a UDPglucose glucosyltransferase gene has been identified that may play a role in controlling the bioactivity of plant hormones or secondary metabolites during drought stress.

Desiccation Tolerance

Drought Tolerance

10.1071/fp06231

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Citations (29)