Molecular characterization of a putative sucrose:fructan 6-fructosyltransferase (6-SFT) of the cold-resistant Patagonian grass Bromus pictus associated with fructan accumulation under low temperatures.

Fructans are fructose polymers synthesized from sucrose in the plant vacuole. They represent short- and long-term carbohydrate reserves and have been associated with abiotic stress tolerance in graminean species. We report the isolation and characterization of a putative sucrose:fructan 6-fructosyltransferase (6-SFT) gene from a Patagonian grass species, Bromus pictus, tolerant to drought and cold temperatures. Structural and functional analyses of this gene were performed by Southern and Northern blot. Sugar content, quality and fructosyltransferase activity were studied using HPAEC-PAD (high-pH anion-exchange chromatography with pulsed amperometric detection), enzymatic and colorimetric assays. The putative 6-SFT gene had all the conserved motifs of fructosyl-transferase and showed 90% identity at the amino acid level with other 6-SFTs from winter cereals. Expression studies, and determination of sugar content and fructosyl-transferase activity were performed on five sections of the leaf. Bp6-SFT was expressed predominantly in leaf bases, where fructosyltransferase activity and fructan content are higher. Bp6-SFT expression and accumulation of fructans showed different patterns in the evaluated leaf sections during a 7 d time course experiment under chilling treatment. The transcriptional pattern suggests that the B. pictus 6-SFT gene is highly expressed in basal leaf sections even under control temperate conditions, in contrast to previous reports in other graminean species. Low temperatures caused an increase in Bp6-SFT expression and fructan accumulation in leaf bases. This is the first study of the isolation and molecular characterization of a fructosyltransferase in a native species from the Patagonian region. Expression in heterologous systems will confirm the functionality, allowing future developments in generation of functional markers for assisted breeding or biotechnological applications.

Linear, steroidal, and triterpene esters, and steryl glycosides from Festuca argentina.

Ester waxes and steryl glycosides of the grass Festuca argentina were studied. Saponification of the waxes from the petroleum ether extract led to n-hexacosanol as the major single linear alcohol, along with pentacyclic triterpenols, such as beta-amyrin, germanicol, isobaurenol, lupeol, hopenol-a and hopeol, and low amounts of sterols, such as cholesterol, campesterol, stigmasterol, sitosterol and dihydrositosterol, identified by gas chromatography/mass spectrometry (GC/MS). Fatty acids were identified as methyl esters as C12:0, C14:0, C16:0, C18:0, C18:2, and C20:0. The occurrence of a wide chainlength range of fatty acids and a single linear alcohol closely matched for other reports on the tribe Festuceae. On the contrary, pentacyclic triterpenols with a variety of skeletons, especially isobauerenol, are not usual as esters of fatty acids in the Gramineae. Low amounts of steryl glycosides were also obtained from the methylene chloride percolate of the methanol extract. Upon acetylation followed by hydrolysis, aglycones were identified by capillary gas-liquid chromatography (GLC) and GC/MS. As delta 7-cholesterol, campesterol, stigmasterol, sitosterol, dihydrositosterol, and the sugars as glucose, xylose, and arabinose by GLC of the respective alditol acetates. This is the first report on the linear, steryl, and triterpenyl esters of F. argentina. It is noteworthy that delta 7-steryl glycosides are rare, and steryl monoarabinosides have not been previously reported on the family Gramineae.

Alkaloids from endophyte-infected Festuca argentina.

Five loline-type alkaloids, the known lolinine, N-formylloline, loline, N-methylloline and the new 5,6-dehydro-N-acetylloline, were characterized from the pooid-grass endophyte-infected Festuca argentina. These compounds are not responsible for the toxicity of the plant, as shown upon i.p. injection into mice. Their probable phytoalexine role and chemotaxonomical significance are discussed.