The distribution and phylogenetic significance of desmethylsterols inChenopodium andAtriplex: Coexistence of Δ7- and Δ5 -sterols

Balance of Δ5-and Δ7-sterols and stanols in halophytes in connection with salinity tolerance

Sterols (STs) have a key role in regulating the fluidity and permeability of membranes in plants (phytosterols) that have wide structural diversity. We studied the effect of structural STs diversity on salt tolerance in halophytes. Specifically, we used gas chromatography-mass spectrometry (GC-MS), including two-dimensional gas chromatography-mass spectrometry (GCxGC-MS), to assess the STs composition in leaves of 21 species of wild-growing halophytes from four families (Asteraceae, Chenopodiaceae, Plumbaginaceae, Tamaricaceae) and three ecological groups (Euhalophytes (Eu), recretophytes (Re), salt excluders (Ex)). Fifteen molecular species of STs from three main groups, Δ⁵-, Δ⁷-and Δ⁰- STs (stanols), were detected. Plants of the genus Artemisia were characterized by a high content of stigmasterol (30-49% of the total STs), while β-sitosterol was the major compound in two Limonium spp., where it comprised 84-92% of the total STs. Species of Chenopodiaceae were able to accumulate both Δ⁵-and Δ⁷-STs and stanols. The content of the predominant Δ⁵-STs decreased in the order Ex → Re → Eu. Molecular species with a saturated steroid nucleus were identified in Eu and Re, suggesting their special salt-accumulating and salt-releasing functions. The structural analogues of stigmasterol, having a double bond C-22, were stigmasta-7,22-dien-3β-ol (spinasterol) and stigmast-22-en-3β-ol (Δ^7--sitosterol). The ratio of Δ⁵-stigmasterol/Δ⁵-β-sitosterol increased in Ex plants, and spinasterol/Δ^7--sitosterol and 22-stigmastenol/sitostanol increased in Eu plants. These data support the well-known role of stigmasterol and its isomers in plant responses to abiotic and biotic factors. The variability in STs types and their ratios suggested some involvement of the sterol membrane components in plant adaptation to growth conditions. The balance of Δ⁵-, Δ⁷-and stanols, as well as the accumulation of molecular analogues of stigmasterol, was suggested to be associated with salt tolerance of the plant species in this investigation.

Isoprenoid-derived plant signaling molecules: biosynthesis and biological importance

The present review summarizes current knowledge of the biosynthesis and biological importance of isoprenoid-derived plant signaling compounds. Cellular organisms use chemical signals for intercellular communication to coordinate their growth, development, and responses to environmental cues. The skeletons of majority of plant signaling molecules, mediators of plant intercellular 'broadcasting', are built from C₅ units of isoprene and therefore belong to a huge and diverse group of natural substances called isoprenoids (terpenoids). They fill many important roles in nature. This review summarizes current knowledge of the biosynthesis and biological importance of a group of isoprenoid-derived plant signaling compounds.

Plant ecdysteroids: plant sterols with intriguing distributions, biological effects and relations to plant hormones

The present review summarises current knowledge of phytoecdysteroids' biosynthesis, distribution within plants, biological importance and relations to plant hormones. Plant ecdysteroids (phytoecdysteroids) are natural polyhydroxylated compounds that have a four-ringed skeleton, usually composed of either 27 carbon atoms or 28-29 carbon atoms (biosynthetically derived from cholesterol or other plant sterols, respectively). Their physiological roles in plants have not yet been confirmed and their occurrence is not universal. Nevertheless, they are present at high concentrations in various plant species, including commonly consumed vegetables, and have a broad spectrum of pharmacological and medicinal properties in mammals, including hepatoprotective and hypoglycaemic effects, and anabolic effects on skeletal muscle, without androgenic side-effects. Furthermore, phytoecdysteroids can enhance stress resistance by promoting vitality and enhancing physical performance; thus, they are considered adaptogens. This review summarises current knowledge of phytoecdysteroids' biosynthesis, distribution within plants, biological importance and relations to plant hormones.

The sterols of Astragalus species from Iran: GLC separation and quantification

This paper presents the content and composition of free sterols in a number of Astragalus species from Iran. Free sterols of roots and seeds were analysed quantitatively and qualitatively by gas-liquid chromatography. Four major 3-beta-hydroxysterols (cholesterol, campesterol, stigmasterol and beta-sitosterol) were identified in roots of 18 species and in seeds of five species of Astragalus. beta-Sitosterol was the main free sterol in both roots and seeds. The cholesterol content in seeds was higher than that in roots. Trace amounts of cholesterol were detected in roots of only four species. beta-Sitosterol accounted for 34.4-69.2 and 76.8-81.8% of the total lipid content in roots and seeds, respectively. The beta-sitosterol content in roots and seeds of Astragalus species varied from 6.3 to 35.7 and 93.3 to 164.5mg/100g dry weight, respectively. Total free sterol content in seeds varied from 112.09 to 204.04mg/100g dry weight, significantly higher than those in roots (7.5 to 43.4mg/100g dry weight). The chemotaxonomic values of free sterols and total lipid profiles of some of the representative species are discussed.

Biosynthesis and distribution of insect-molting hormones in plants--a review

Insect-molting hormones, phytoecdysteroids, have been reported to occur in over 100 plant families. Plants, unlike insects, are capable of the biosynthesis of ecdysteroids from mevalonic acid, and in several cases the biosynthesis of phytoecdysteroids was also demonstrated to proceed via sterols. Spinacia oleracea (spinach) biosynthesizes polypodine B and 20-hydroxyecdysone, which is the predominant insect-molting hormone found in plant species. The onset of ecdysteroid production in spinach requires the appropriate ontogenetic development within the plant, which is related to leaf development. In spinach, lathosterol is the biosynthetic precursor to ecdysone and 20-hydroxyecdysone. Phosphorylated ecdysteroid intermediates, particularly ecdysone-3-phosphate, are required during biosynthesis. Polyphosphorylated forms of ecdysteroids are putative regulatory components of the pathway. During spinach development, the 20-hydroxyecdysone is transported from the sites of biosynthesis to the apical regions. An analysis of the physiological data available suggests that different species may synthesize ecdysteroids in various organs and distribute these ecdysteroids to other sites. Annual plants appear to concentrate ecdysteroids in the apical regions, including flowers and seeds. Perennial plants may recycle their ecdysteroids between their deciduous and their perennial organs over the growing season. Further investigations of ecdysteroid biosynthesis and physiology within plants will be required before an acceptable system can be designed to test phytoecdysteroid effectiveness in vivo against insect herbivory.