Importance of plant sterols in pattern formation and hormone signalling

Lindsey, Keith; Pullen, Margaret; Topping, Jennifer F.

doi:10.1016/j.tplants.2003.09.012

Cited by 136 publications

(100 citation statements)

References 30 publications

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“…Recent findings with the aid of molecular genetics approaches have suggested possible involvement of phytosterols in BRindependent processes of embryonic and postembryonic development (Clouse, 2000;Lindsey et al, 2003). Thus, Arabidopsis thaliana mutants in the sterol biosynthetic pathway (Figure 1) display severe impairment in embryogenesis and development at specific stages, which cannot be rescued by the application of exogenous BRs.…”

Section: Introductionmentioning

confidence: 99%

Cytochrome P450CYP710AEncodes the Sterol C-22 Desaturase inArabidopsisand Tomato

et al. 2006

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D22-Unsaturated sterols, containing a double bond at the C-22 position in the side chain, occur specifically in fungi and plants. Here, we describe the identification and characterization of cytochrome P450s belonging to the CYP710A family as the plant C-22 desaturase. Recombinant proteins of CYP710A1 and CYP710A2 from Arabidopsis thaliana and CYP710A11 from tomato (Lycopersicon esculentum) were expressed using a baculovirus/insect system. The Arabidopsis CYP710A1 and tomato CYP710A11 proteins exhibited C-22 desaturase activity with b-sitosterol to produce stigmasterol (CYP710A1, K m ¼ 1.0 mM and kinetic constant [k cat ] ¼ 0.53 min ÿ1 ; CYP710A11, K m ¼ 3.7 mM and k cat ¼ 10 min ÿ1 ). In Arabidopsis transgenic lines with CYP710A1 and CYP710A11 overexpression, stigmasterol levels increased by 6-to 32-fold. Arabidopsis CYP710A2 was able to produce brassicasterol and stigmasterol from 24-epi-campesterol and b-sitosterol, respectively. Sterol profiling analyses for CYP710A2 overexpression and a T-DNA insertion event into CYP710A2 clearly demonstrated in planta that CYP710A2 was responsible for both brassicasterol and stigmasterol production. Semiquantitative PCR analyses and promoter:b-glucuronidase transgenic approaches indicated strict tissue/organ-specific regulation for each CYP710A gene, implicating differential tissue distributions of the D 22 -unsaturated sterols in Arabidopsis. Our results support the possibility that the CYP710 family may encode P450s of sterol C-22 desaturases in different organisms.

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Section: Introductionmentioning

confidence: 99%

Cytochrome P450CYP710AEncodes the Sterol C-22 Desaturase inArabidopsisand Tomato

et al. 2006

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“…Sterols are essential constituents of eukaryotic membranes and play multiple roles in membrane organization, dynamics, function and sorting (Lindsey et al, 2003). Intermolecular interactions between sterols and membrane lipids modulate the physical state of the bilayer via restricting the mobility of the fatty acyl chains and in turn regulate the membrane fluidity and permeability (Hartmann, 1998).…”

Section: Introductionmentioning

confidence: 99%

Effect of Membrane Fluidity on Photosynthetic Oxygen Production Reactions

Popova

Velitchkova

Zanev

2007

Zeitschrift Für Naturforschung C

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The effect of changes of membrane fluidity on the oxygen evolving capability of isolated thylakoids was investigated. Alteration of the lipid phase fluidity was achieved by incorporation of the plant sterol stigmasterol. Incorporation of stigmasterol in the lipid bilayer of thylakoid membranes results in rigidization of the hydrophobic phase of thylakoid membranes and decreases the degree of packing of the lipid head groups. These changes of lipid order are accompanied by a reduction of oxygen evolution, measured with 1,4-benzoquinone as an electron acceptor, and by a more pronounced inhibition of PSI-mediated electron transport. By analysis of the parameters of oxygen flash yields and oxygen burst under continuous illumination it was shown that after treatment with stigmasterol: 1.) the number of active oxygen-evolving centres decreased; 2.) the remaining active oxygen-evolving centres were not affected in respect to the oscillation pattern; 3.) the contribution of the slow oxygenevolving centres in oxygen burst yield was increased. The effect of stigmasterol was compared with the well-studied effect of cholesterol. Results were discussed in terms of determining the role of lipid order for the organization and functioning of the photosynthetic machinery.

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“…Phytosterols play important roles in plants: as structural molecules in membranes (Hartmann, 1998), as plant growth and development factors (Clouse, 2002), and as hormone signaling molecules (Lindsey et al, 2003;Men et al, 2008). For all of these roles, the elimination of the two methyl groups at C4 is a central feature of the biosynthesis and biological function of sterols.…”

Section: Outlook On the Essential Role Of The Sterol C4-demethylationmentioning

confidence: 99%

“…It has been suggested that sterols other than brassinolides may serve as novel signals controlling cell fate during plant embryogenesis (Clouse, 2002;Lindsey et al, 2003). Indeed, in plants, sterol biosynthetic mutants upstream of the last biosynthetic intermediate possessing one C4-methyl group (i.e.…”

Section: Outlook On the Essential Role Of The Sterol C4-demethylationmentioning

confidence: 99%

Homology Modeling and Site-Directed Mutagenesis Reveal Catalytic Key Amino Acids of 3β-Hydroxysteroid-Dehydrogenase/C4-Decarboxylase from Arabidopsis

et al. 2009

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Sterols become functional only after removal of the two methyl groups at C4 by a membrane-bound multienzyme complex including a 3b-hydroxysteroid-dehydrogenase/C4-decarboxylase (3bHSD/D). We recently identified Arabidopsis (Arabidopsis thaliana) 3bHSD/D as a bifunctional short-chain dehydrogenase/reductase protein. We made use of three-dimensional homology modeling to identify key amino acids involved in 4a-carboxy-sterol and NAD binding and catalysis. Key amino acids were subjected to site-directed mutagenesis, and the mutated enzymes were expressed and assayed both in vivo and in vitro in an erg26 yeast strain defective in 3bHSD/D. We show that tyrosine-159 and lysine-163, which are oriented near the 3b-hydroxyl group of the substrate in the model, are essential for the 3bHSD/D activity, consistent with their involvement in the initial dehydrogenation step of the reaction. The essential arginine-326 residue is predicted to form a salt bridge with the 4a-carboxyl group of the substrate, suggesting its involvement both in substrate binding and in the decarboxylation step. The essential aspartic acid-39 residue is in close contact with the hydroxyl groups of the adenosine-ribose ring of NAD + , in good agreement with the strong preference of 3bHSD/D for NAD + . Data obtained with serine-133 mutants suggest close proximity between the serine-133 residue and the C4b domain of the bound sterol. Based on these data, we propose a tentative mechanism for 3bHSD/D activity. This study provides, to our knowledge, the first data on the three-dimensional molecular interactions of an enzyme of the postoxidosqualene cyclase sterol biosynthesis pathway with its substrate. The implications of our findings for studying the roles of C4-alkylated sterol precursors in plant development are discussed.

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Importance of plant sterols in pattern formation and hormone signalling

Cited by 136 publications

References 30 publications

Cytochrome P450CYP710AEncodes the Sterol C-22 Desaturase inArabidopsisand Tomato

Cytochrome P450CYP710AEncodes the Sterol C-22 Desaturase inArabidopsisand Tomato

Effect of Membrane Fluidity on Photosynthetic Oxygen Production Reactions

Homology Modeling and Site-Directed Mutagenesis Reveal Catalytic Key Amino Acids of 3β-Hydroxysteroid-Dehydrogenase/C4-Decarboxylase from Arabidopsis

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