Sterol composition and synthesis in potato tuber discs in relation to glycoalkaloid synthesis

Bergenstråhle, Annika; Borgå, Peter; Jonsson, Lisbeth

doi:10.1016/0031-9422(95)00554-4

Cited by 28 publications

(19 citation statements)

References 25 publications

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“…24-methylcholesterol, sitosterol, and stigmasterol). It is of special interest in view of the role of cholesterol as the precursor of various secondary products such as glycoalkaloids (Bergenstråhle et al 1996). Cholesterol has been also found to accumulate at specific stages of development, especially early in floral development (Hobbs et al 1996).…”

Section: Sterol Methyl Transferasesmentioning

confidence: 99%

“…It generally accounts for a few percent of the sterol mixture of most plants, but amounts to 30 to 40% in members of some families (e.g. Solanaceae, Liliaceae, and Scrophylariaceae), where it serves as a precursor of steroidal saponins and glycoalkaloids (Bergenstråhle et al 1996). In early stages of apical development of Brassica campestris (Hobbs et al 1996) or in the epicuticular waxes of rape leaves (Noda et al 1988), cholesterol represents around 70 % of total sterols.…”

Section: Sterol Structural Diversity and Occurrence In Higher Plantsmentioning

confidence: 99%

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5 Sterol metabolism and functions in higher plants

Hartmann

2003

Lipid Metabolism and Membrane Biogenesis

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Higher plants synthesize a bewildering array of sterols, with sitosterol, stigmasterol, and 24-methylcholesterol as major compounds. All plant tissues contain free and conjugated sterols. The first steps of sterol biosynthesis occur via the classical acetate/mevalonate pathway, concomitantly with synthesis of many other isoprenoids. A crosstalk between cytosolic and plastid 2-C-methylerythritol phosphate pathways has been clearly demonstrated. Squalene synthase is the first enzyme of the sterol branch. All subsequent steps occur within the endoplasmic reticulum. In addition to their recognized role in regulating membrane properties, sitosterol, and 24-methylcholesterol modulate a variety of metabolic and ontogenetic events. The enzyme 3-hydroxy-3-methylglutaryl CoA reductase is a rate-limiting step for carbon flux toward sterols and also positively or negatively responds to a depletion of endogenous sterols or accumulation of intermediates. Sterol methyltransferases and acyltransferase participate in sterol homeostasis. A coordinated regulation of the biosynthetic pathways of sterols and some specific lipids may occur during membrane biogenesis.

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Section: Sterol Methyl Transferasesmentioning

confidence: 99%

Section: Sterol Structural Diversity and Occurrence In Higher Plantsmentioning

confidence: 99%

5 Sterol metabolism and functions in higher plants

Hartmann

2003

Lipid Metabolism and Membrane Biogenesis

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“…Moreover, enzymes involved in the biosynthesis of sterols, such as cholesterol (7-dehydrocholesterol reductase), were up-regulated in S. nigrum. Sterol contents in Solanum species are tightly linked to levels of glycoalkaloids, and cholesterol is thought to be a precursor of steroidal alkaloids (Bergenstrahle et al, 1996), which in turn suggests increased production of glycoalkaloids in S. nigrum in response to M. sexta feeding. Further evidence for the deployment of alkaloidal defenses in S. nigrum is the up-regulation of a 2-oxoglutaratedependent dioxygenase, which is homologous to hyoscyamine 6b-hydroxylase of Hyoscyamus niger (Lantin et al, 1999).…”

Section: Secondary Metabolismmentioning

confidence: 99%

Specificity in Ecological Interactions. Attack from the Same Lepidopteran Herbivore Results in Species-Specific Transcriptional Responses in Two Solanaceous Host Plants

et al. 2005

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Model systems have proven enormously useful in elucidating the biochemical function of plant genes. However their ecological function, having been sculpted by evolutionary forces specific to a species, may be less conserved across taxa. Responses to wounding and herbivore attack differ among plant families and are known to be mediated by oxylipin, ethylene, and systemin-signaling networks. We analyzed transcriptional responses of two native Solanaceous species to the attack of an herbivore whose elicitors are known not to be influenced by diet. With The Institute for Genomic Research 10k-cDNA potato (Solanum tuberosum) microarray, we compared the transcriptional responses of Nicotiana attenuata with those of black nightshade (Solanum nigrum) when both were attacked by the Solanaceous generalist herbivore, Manduca sexta. Based on an NADH dehydrogenase subunit F phylogeny, S. nigrum is more closely related to potato than N. attenuata but responded significantly less to M. sexta attack. Apart from transcriptional differences anticipated from their differences in secondary metabolism, both species showed distinct transcriptional patterns (with only 10% overlap in significantly regulated genes), which point to fundamental differences in the signaling cascades and downstream genes mediating herbivore resistance. The lackluster transcriptional response of S. nigrum could not be attributed to its inability to respond to elicitation, because methyl jasmonate elicitation of S. nigrum resulted in a strong transcriptional response. Given that attack from the same herbivore elicits profoundly different responses in two Solanaceaous taxa, we conclude that blueprints for commonly regulated responses to plant-herbivore interactions appear unlikely.

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“…The SMT1 acts at the branching point between cholesterol and the 24-alkylated sterols, and is of special interest in view of the proposed role of cholesterol as the precursor for various secondary compounds with a steroid skeleton, such as the poisonous glycoalkaloids in potato (BergenstraÊ hle et al 1996). Furthermore, reports from studies of sterol composition and SMT activity in potato slices (Hartmann and Benveniste 1974;BergenstraÊ hle et al 1993) and of transgenic tobacco plants overproducing sterols as a consequence of increased expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (Schaller et al 1995) indicate that SMT under the experimental conditions has a rate-regulatory role in the overall biosynthesis of sterols.…”

Section: Introductionmentioning

confidence: 99%

Sterol composition and growth of transgenic tobacco plants expressing type-1 and type-2 sterol methyltransferases

Sitbon

Jonsson

2001

Planta

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Transgenic tobacco (Nicotiana tabacum L.) plants with altered sterol composition were generated by transformation with plant cDNAs encoding type-1 and type-2 sterol methyltransferases (SMTs; EC 2.1.1.41). For both SMT1 and SMT2 transformants, the transformation was associated with a reduction in the level of cholesterol, a non-alkylated sterol. In SMT1 transformants a corresponding increase of alkylated sterols, mainly 24-methyl cholesterol, was observed. On the other hand, in SMT2 transformants the level of 24-methyl cholesterol was reduced, whereas the level of sitosterol was raised. No appreciable alteration of total sterol content was observed for either genotype. The general phenotype of transformants was similar to that of controls, although SMT2 transformants displayed a reduced height at anthesis. The results show that plant sterol composition can be altered by transformation with an SMT1 cDNA without adverse effects on growth and development, and provide evidence, in planta, that SMT1 acts at the initial step in sterol alkylation.

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Sterol composition and synthesis in potato tuber discs in relation to glycoalkaloid synthesis

Cited by 28 publications

References 25 publications

5 Sterol metabolism and functions in higher plants

5 Sterol metabolism and functions in higher plants

Specificity in Ecological Interactions. Attack from the Same Lepidopteran Herbivore Results in Species-Specific Transcriptional Responses in Two Solanaceous Host Plants

Sterol composition and growth of transgenic tobacco plants expressing type-1 and type-2 sterol methyltransferases

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