Gene family of oleosin isoforms and their structural stabilization in sesame seed oil bodies.
Oleosins are structural proteins sheltering the oil bodies of plant seeds. Two isoform classes termed H- and L-oleosin are present in diverse angiosperms. Two H-oleosins and one L-oleosin were identified in sesame oil bodies from the protein sequences deduced from their corresponding cDNA clones. Sequence analysis showed that the main difference between the H- and L-isoforms is an insertion of 18 residues in the C-terminal domain of H-oleosins. H-oleosin, presumably derived from L-oleosin, was duplicated independently in several species. All known oleosins can be classified as one of these two isoforms. Single copy or a low copy number was detected by Southern hybridization for each of the three oleosin genes in the sesame genome. Northern hybridization showed that the three oleosin genes were transcribed in maturing seeds where oil bodies are being assembled. Artificial oil bodies were reconstituted with triacylglycerol, phospholipid, and sesame oleosin isoforms. The results indicated that reconstituted oil bodies could be stabilized by both isoforms, but L-oleosin gave slightly more structural stability than H-oleosin. (+info)
Enhanced methionine and cysteine levels in transgenic rice seeds by the accumulation of sesame 2S albumin.
A chimeric gene encoding a precursor polypeptide of sesame 2S albumin, a sulfur-rich seed storage protein, was expressed in transgenic rice plants under the control of the glutelin promoter with the aim of improving the nutritive value of rice. Rice grains harvested from the first generation of ten different transformed lines inherited the transgene, and the accumulated sesame 2S albumin was presumably processed correctly as its mature form in sesame seed. This transgene was specifically expressed in maturing rice seeds with its encoded sesame 2S albumin exclusively accumulated in the seeds. The crude protein content in rice grains from five putative homozygous lines was increased by 0.64-3.54%, and the methionine and cysteine contents of these transgenic rice grains were respectively elevated by 29-76% and 31-75% compared with those of wild-type rice grains. (+info)
A novel method for producing a foodstuff from defatted black sesame seed that inhibits allergen absorption.
A method is proposed to produce a foodstuff that inhibits allergen absorption through the intestinal tract. Defatted black sesame (Sesamum indicum) seeds as a starting material were hydrolyzed with a crude preparation of trypsin at 40 degrees C and pH 8 for 3 hrs while gently stirring to generate an active peptide. The resulting hydrolysate was heated to inactivate the trypsin and make the active components soluble. An extract was obtained by centrifugation and then freeze-dried. Ser-Asn-Ala-Leu-Val-Ser-Pro-Asp-Trp-Ser-Met-Thr-Gly-His (compound 1) as an active peptide, and sesamino1 2'-O-beta-glucopyranosyl-(1-->2)-O-[beta-glucopyranosyl(1-->6)]-O-beta-glucopyran oside (compound 2) and sesamino1 2'-O-beta-glucopyranosyl (1-->2)-O-beta-glucopyranoside (compound 3) were identified as active lignan glycosides in an in vitro model by using Caco-2 cells. Compound 1 was active at 10(-7) M and compounds 2 and 3 at 10(-5) M. (+info)
Activation of phenylpropanoid metabolism in sesame by over-expression of carrot calmodulin gene.
Transgenic sesame (Sesamum schinzianum ASCH.) was produced by Agrobacterium-mediated transfection of a carrot calmodulin gene, cam-4, which was specifically expressed upon the contact of carrot cells with oligogalacturonide elicitor. Coding region of cam-4 was ligated to the downstream of 35S promoter of cauliflower mosaic virus and subcloned into pMATGBO-DB3.1. A. tumefaciens 4404 was transformed with the constructed vector, and the crown gall tissues formed in the sesame seedlings were transferred onto appropriate media to obtain the re-differentiated plants. The reverse-transcription polymerase chain reaction followed by Southern blot analysis revealed that cam-4 gene was appreciably expressed in the transgenic plants. Activities of two key enzyme regulating phenylpropanoid metabolisms, phenylalanine ammonia-lyase and caffeic acid O-methyltransferase, and the contents of phenolic compounds in the transformed sesame were markedly elevated as compared with those of the control. These results suggest that the over-expression of cam-4 gene enhances the biosynthetic activities of phenylpropane derivatives in the transformed sesame plants. (+info)
Modulating effect of sesamin, a functional lignan in sesame seeds, on the transcription levels of lipid- and alcohol-metabolizing enzymes in rat liver: a DNA microarray study.
Sesamin, a major lignan in sesame seeds, has multiple functions such as cholesterol-lowering and anti-hypertensive activities. To investigate the effect of sesamin on gene expression in the liver, a DNA microarray analysis was carried out. The ingestion of sesamin dissolved in olive oil up-regulated the expression of 38 genes, 16 of which encode proteins possessing a lipid-metabolizing function, and 16 of which encode proteins possessing a xenobiotic/endogenous substance metabolizing function. In particular, sesamin significantly increased the expression of beta-oxidation-associated enzymes in peroxisomes and auxiliary enzymes required for degradation, via the beta-oxidation pathway, of unsaturated fatty acids in mitochondria. The ingestion of sesamin also resulted in an increase in the gene expression of acyl-CoA thioesterase involved in acyl-CoA hydrolase and very-long-chain acyl-CoA thioesterase. Interestingly, it induced the expression of the gene for aldehyde dehydrogenase, an alcohol-metabolizing enzyme. These results suggest that sesamin regulates the metabolism of lipids, xenobiotics, and alcohol at the mRNA level. (+info)
Thermostability and in vitro digestibility of a purified major allergen 2S albumin (Ses i 1) from white sesame seeds (Sesamum indicum L.).
A major 2S albumin allergen, Ses i 1, from white sesame seeds was purified to homogeneity, characterized and identified using proteomic techniques. Ses i 1 exhibited a molecular weight of 12062 Da, although an extensive C-terminal clipping of the small subunit was observed. In addition, the N-terminal glutamine of the small subunit had been converted to pyroglutamate and a variant of the large subunit which had lost the N-terminal glutamine was also detected. The protein was thermo-stable up to 90 degrees C at neutral and acid pH, retaining its monomeric state and showing minimal alterations, which were reversible on cooling, in a predominantly alpha-helical secondary structure, as shown by circular dichroism and Fourier transform-infrared spectroscopy. Ses i 1 was also highly resistant to digestion using a physiologically relevant in vitro gastrointestinal model system. After 2 h of gastric digestion, the allergen remained completely intact and only the small subunit was cleaved during 2 h of subsequent duodenal digestion, leaving a major IgE epitope region of this protein intact. Neither prior heating of the Ses i 1 nor the presence of the physiological surfactant phosphatidylcholine affected the pattern of proteolysis. These findings are consistent with those found for the 2S albumin allergen from Brazil nut, Ber e 1, and suggest that Ses i 1 may preserve its structure from the degradation in the gastrointestinal tract, a property thought to be crucial for both a protein to sensitise the mucosal immune system and provoke an allergic reaction in a sensitised individual. (+info)
Sesame seed products contaminated with Salmonella: three outbreaks associated with tahini.
In November 2002, the first of three outbreaks of Salmonella Montevideo infection in Australia and New Zealand was identified in New South Wales, Australia. Affected persons were interviewed, and epidemiologically linked retail outlets inspected. Imported tahini was rapidly identified as the source of infection. The contaminated tahini was recalled and international alerts posted. A second outbreak was identified in Australia in June-July 2003 and another in New Zealand in August 2003. In a total of 68 S. Montevideo infections, 66 cases were contacted. Fifty-four (82%) reported consumption of sesame seed-based foods. Laboratory analyses demonstrated closely related PFGE patterns in the S. Montevideo isolates from human cases and sesame-based foods imported from two countries. On the basis of our investigations sesame-based products were sampled in other jurisdictions and three products in Canada and one in the United Kingdom were positive for Salmonella spp., demonstrating the value of international alerts when food products have a wide distribution and a long shelf life. A review of the controls for Salmonella spp. during the production of sesame-based products is recommended. (+info)
Cloning and expression of a seed-specific metallothionein-like protein from sesame.
A cDNA clone, SiMT encoding an Ec type of metallothionein (MT)-like protein, was isolated from maturing seeds of sesame (Sesamum indicum L.), and its deduced protein sequence shared 47-65% similarity to other known Ec type of MT-like proteins with three highly conserved cysteine-rich segments. The transcript of SiMT was exclusively accumulated in maturing seeds from two weeks after flowering to the end of seed maturation. The results of a southern blot analysis suggested that one SiMT and one SiMT-like gene were present in the sesame genome. Recombinant SiMT fused with glutathione-S-transferase (GST) was over-expressed in Escherichia coli, and purified to homogeneity by affinity chromatography. Recombinant SiMT released from GST was harvested after factor Xa cleavage. Migration of the recombinant SiMT during SDS-PAGE was accelerated when its binding metal ions were depleted by EDTA. The metal-binding capability of recombinant SiMT was measured by inductively-coupled plasma atomic emission spectrometry. Our results show that the recombinant SiMT could trap zinc or copper ions, but not manganese ions, with a stoichiometric ratio (metal ion/SiMT) of approximately 2. (+info)