Chemical composition of teff (Eragrostis tef) compared with that of wheat,barley and grain sorghum

The chemical composition of teff, analyzed from uncontaminated seeds, revealed the superiority of the species in mineral nutritive value. Teff’s exceedingly high iron and calcium content was confirmed. The high iron content of teff reported by the Ethiopia Nutrition Survey must have been due to certain inherent factors of the species, not only a result of contamination. The magnitude of mineral absorption varied among tested teff strains which was considered an important criterion for future selection program within the species.     

Microbial flora and some chemical properties of ersho,a starter for teff (Eragrostis tef) fermentation

Ersho is a clear, yellow liquid that accumulates on the surface of fermenting teff-flour batter and is collected to serve as an inoculum for the next fermentation. The pH of ersho samples was about 3.5 and titratable acidity ranged between 3.1% and 5.7%. The mean aerobic mesophilic counts from four households varied between 6.9×10⁶ and 1.3×10⁸ c.f.u./ml and the aerobic bacterial flora consisted of Bacillus spp. Mean yeast counts ranged between 5.2×10⁵ and 1.8×10⁶ c.f.u./ml and comprised, in order of abundance, Candida milleri, Rhodotorula mucilaginosa, Kluyveromyces marxianus, Pichia naganishii and Debaromyces hansenii. Candida milleri was the most dominant isolate in all samples. About 90% of the teff flour samples had aerobic mesophilic counts 10⁵ c.f.u./g and Gram-positive bacteria constituted about 71% of the total isolates. About 80% of samples had Enterobacteriaceae counts of 10⁴ c.f.u./g.M. Ashenafi is with the Department of Basic Sciences, Awassa College of Agriculture, Addis Ababa University, PO Box 5, Awassa, Sidamo, Ethiopia.     

RFLP linkage map of the Ethiopian cereal tef [Eragrostis tef (Zucc) Trotter]

Tef [Eragrostis tef (Zucc)Trotter] is one of the most important cereal crops in Ethiopia. It is an allotetraploid species with a genome size of 720 Mbp. In this paper we report results of genetic linkage-map construction for E. tef using tef and heterologous cDNA probes for the first time. One hundred and sixteen F₈ recombinant inbred lines (RILs) from the cross E. tef cv Kaye Murri×Eragrostis pilosa (accession30–5) were used for mapping. Parental lines were digested with nine restriction enzymes and screened using 159 tef cDNA and 162 heterologous probes including the grass genome anchor probes. The polymorphism level between parental lines was 66.9%. One hundred and thirty nine polymorphic probes were hybridized against 116 RILs. Both the tef and the heterologous probes hybridized well against tef genomic DNA. The linkage map defined 1,489 cM of the tef genome comprising 149 marker loci distributed among 20 linkage groups. The average interval between markers was 9.99 cM. A fraction (14.8%) of the markers deviated significantly from the expected segregation. Such a genetic linkage map is useful for tagging economically useful genes in tef because a wide range of agronomically important traits is segregating within this population. This would enable the use of a marker assisted breeding strategy which, in turn, will enhance breeding efficiency. Alignment of the tef RFLP map with the rice RFLP map indicates that a number of syntenic chromosomal fragments exist between tef and rice in which the gene order was for the most part collinear. The comparative mapping information should enable tef scientists to take advantage of whatever genetic progress is made on the cereal model species rice. Received: 9 June 2000 / Accepted: 31 August 2000     

In vitro normal and variant development of t'ef (Eragrostis tef) spikelets

Spikelets of t'ef, Eragrostis tef were cultured from the pre-anthesis stage to seed maturation, although only a small proportion of these seeds germinated to produce adult plants. A liquid culture medium originally formulated for wheat spikelets was used and it is of interest that grass stigmas normally classified as dry function under these conditions. Varietal differences of response were observed and examples were found where although seed setting within the spikelet was less than under in vivo situation. The implications are considered for spikelet culture in an old genus such as Eragrostis where one species, E. tef, is recognised as conspicuously variable.     

Effect of gibberellic acid on starch degrading enzymes in leaves of Digitaria decumbens

Tropical ‘Pangola’ digitgrass was treated with gibberellic acid (GA) and subjected to 30° or 10° nights. The starch degrading enzymes of the leaves were separated by polyacrylamide gel electrophoresis. Densitometer tracings of gels negatively stained by starch-iodine showed the presence of seven bands regardless of treatment of plants. GA treatment increased starch degrading enzyme activity in plants subjected to 10° to the level of activity found in 30° untreated (control) plants and, additionally, enhanced enzyme activity in plants at 30°. GA treatment of 10° plants decreased sucrose and starch levels when compared to levels found in untreated 10° plants. The action of GA in reversing the effects of 10° nights on ‘Pangola’ leaves was found to be the result of a quantitative increase in activity of existing enzyme forms rather than production of isozymes.     

Gynogenic plant regeneration from unpollinated flower explants of Eragrostis tef (Zuccagni) Trotter

Tef [Eragrostis tef (Zucc.) Trotter] is the most important cereal in Ethiopia. In its wild relative E. mexicana, regeneration of six green plants resulted from culture of 121 non-pollinated immature pistils. In the allotetraploid crop species tef, however, only callus and root formation was obtained by this method. By contrast, immature spikelets and panicle segments of E. tef proved amenable to gynogenic plant regeneration. Upon step-wise optimization of the protocol, efficient plant formation was achieved in all three cultivars tested. In cv. DZ-01-196, culture of 1305 immature spikelets resulted in formation of 159 green plants. Flow cytometric analysis revealed (di)haploid, triploid, tetraploid and octoploid regenerants, from which the vast majority was tetraploid. Tef-breeding programs will likely benefit substantially from efficient generation of true-breeding plants.     

The effect of the etched (et) mutation on the amylolytic enzyme activities in germinating kernels and seedlings of Zea mays

Summary The etched (et) mutation in maize causes distinct depressions and structural gaps in the endosperm and also gives rise to virescent seedlings, - and -Amylase activities were observed to be higher in et ⁺ et ⁺ kernels and seedlings as compared to that of the et et mutant. The total amylase and -amylase trends during germination also differed between normal and mutant kernels and seedlings (it increases in the wildtype and decreases in et et). On the contrary, the overall -amylase trend was found to be similar in both genotypes (slight decrease during germination). The native gel electrophoresis of crude enzyme extracts did not reveal any qualitative differences in and amylases during germination. The germinating et et kernels initially showed lower levels of starch compared with the wild type kernels, whereas no such difference was found at later stages of germination. It is concluded that et gene associated endosperm lesions lead to an impairment of starch degradation in germinating kernels resulting in virescent seedlings.     

Larvicidal potential of cell wall degrading enzymes from Trichoderma asperellum against Aedes aegypti (Diptera: Culicidae)

Aedes aegypti is a mosquito vector of arboviruses such as dengue, chikungunya, zika and yellow fever that cause important public health diseases. The incidence and gravity of these diseases justifies the search for effective measures to reduce the presence of this vector in the environment. Bioinsecticides are an effective alternative method for insect control, with added ecological benefits such as biodegradability. The current study demonstrates that a chitinolytic enzyme complex produced by the fungus Trichoderma asperellum can disrupt cuticle formation in the L3 larvae phase of A. aegypti, suggesting such biolarvicidal action could be used for mosquito control. T. asperellum was exposed to chitin from different sources. This induction of cell wall degrading enzymes, including chitinase, N-acetylglucosaminidase and β-1,3-glucanase. Groups of 20 L3 larvae of A. aegypti were exposed to varying concentrations of chitinolytic enzymes induced with commercial chitin (CWDE) and larvae cell wall degrading enzymes (L-CWDE). After 72 h of exposure to the CWDE, 100% of larvae were killed. The same percent mortality was observed after 48 h of exposure to L-CWDE at half the CWDE enzyme mixture concentration. Exoskeleton deterioration was further observed by scanning and electron microscopy. Our findings indicate that L-CWDE produced by T. asperellum reflect chitinolytic enzymes with greater specificity for L3 larval biomolecules. This specificity is characterized by the high percentage of mortality compared with CWDE treatments and also by abrupt changes in patterns of the cellular structures visualized by scanning and transmission electron microscopy. These mixtures of chitinolytic enzymes could be candidates, as adjuvant or synergistic molecules, to replace conventional chemical insecticides currently in use.     

Thermal stability of soluble mitochondrial H+-ATPase

ATPase melting has been studied by circular dichroism and differential scanning microcalorimetry. Decomposition of the -helix of H⁺-ATPase (in which about 80% of the peptide groups of the enzyme are involved) following thermal treatment is shown to proceed gradually, beginning with room temperature. Effect of nucleotides upon melting is detected in the range of 20–40 C. Above 40 C, the pattern of thermal decomposition of the three-dimensional structure of H⁺-ATPase is independent of the nature of nucleotides present. Highly stable -helical sites have been found in the enzyme molecule. Possible mechanism of formation of such sites is discussed, and the results obtained are compared with data on thermal stability of ATPase from thermophilic bacteria. Structural changes in the molecule following thermal treatment are compared with ATPase activity changes under similar experimental conditions.     

Thermal stability of Artemia HGPRT: effect of substrates on inactivation kinetics

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT, E.C. 2.4.2.8) from Artemia cysts exhibits maximum activity at 70°C. Its thermal stability has been examined following enzymatic activity as a function of temperature. Cold-induced renaturation experiments of samples heated at increasing temperatures showed that reversibility of thermal inactivation depends on the incubation time and final temperature. Prolonged incubation of the thermoinactivated enzyme at 0°C did not afford any further increase of the catalytic activity at 37°C. The complex substrate PRPP:Mg protects HGPRT from thermal inactivation. However, incubations with hypoxanthine rendered a less thermostable enzyme at any temperature tested. The irreversible inactivation of HGPRT proceeds in two exponential steps. The analysis of the apparent rate constants for the fast and the slow phases, λ₁ and λ₂ as per the Lumry and Eyring model suggests the existence of more than three states in the thermal denaturation pathway of the free enzyme. In the presence of PRPP:Mg the irreversible process follows a single exponential and proceeds very slowly below 70°C. PRPP:Mg also protects the enzyme from inactivation by NEM and pCMB, suggesting that -SH groups may be in the vicinity of the active site     

Thermal stability of bovine-brain myelin membrane

The thermal behaviour of bovine-brain myelin membrane has been studied by high-sensitivity differential scanning calorimetry, Fourier-transform infrared spectroscopy and thermal gel analysis. Spectroscopic results indicate that protein transitions take place between 60°C and 90°C, while thermal gel analysis has provided the thermal denaturation profiles of myelin proteolipid, DM-20 protein and the Wolfgram Fraction. An irreversible calorimetric transition centred at 80.3 ± 0.2°C with a specific enthalpy of 4.7 ± 0.6 J/g of total protein has been assigned to the thermal denaturation of myelin proteolipid and DM-20 protein. The effects of the myelin storage conditions, scan rate, ionic strength and pH on this calorimetric transition have also been investigated. The thermal transition of the proteolipid practically disappears after treatment of the myelin with different amounts of chloroform-methanol 2:1 (v/v), a treatment which is generally used in proteolipid purification. On the other hand, the addition of several detergents to myelin only causes minor modifications to this transition, which then occurs at about 70°C, with a specific enthalpy of between 2.5 and 3.6 J/g of total protein. These results appear to show that detergents preserve the native conformation of the proteolipid far more than do organic solvents. Hence the use of detergents would seem to be the appropriate method for proteolipid purification.Abbreviations DSC Differential scanning calorimetry - TGA Thermal gel analysis - FTIR Fourier-transform infrared spectroscopy - PLP Proteolipid protein - MBP Myelin basic protein - DM-20 Protein DM-20 - WF Wolfgram fraction - BSA Bovine serum albumine - SDS Sodium dodecyl sulfate - ANSA 4-amino-3-hydroxynaphthalene-1-sulphonic acid - OG -d-glucopyranoside - PAGE Polyacrylamide gel electrophoresis - Chaps 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate - CNS Central nervous system Correspondence to: P. L. Mateo     

Characterization of technological features of dry yeast (strain I-7-43) preparation, product of electrofusion between Saccharomyces cerevisiae and Saccharomyces diastaticus, in industrial application

The aim of the study was to verify the technological usability and stability of biotechnological features of active dry distillery yeast preparation (strain I-7-43 with amylolytic abilities) applied to full-scale production of agricultural distillery. Various reduced doses of glucoamylase preparation (San-Extra L) were used for starch saccharification, from 90% to 70% in relation to the full standard dose of preparation. The dry distillery yeast I-7-43 were assessed positively in respect to fermentation activity and yield of ethanol production. Application of the dry yeast I-7-43 preparation in distillery practice lowers the costs of spirit production by saving the glucoamylase preparation (up to 30%) used in the process of mash saccharification. Concentrations of the volatile fermentation by-products in raw spirits obtained from fermentations with application of I-7-43 strain were on the levels guaranteeing good organoleptic properties of distillates.     

Thermal stability of oligodeoxynucleotide duplexes containing l-deoxynucleotide at termini

The effects of substituting l-deoxynucleotide for d-deoxynucleotide at duplex termini were evaluated and the terminal substitutions were found to show much less effects on duplex destabilization and to show a similar tendency in base pairing selectivity, compared with internal chiral substitutions.     

High stability to irreversible inactivation at elevated temperatures of enzymes covalently modified by hydrophilic reagents: alpha-Chymotrypsin

Based on the idea that proteins can be stabilized by a decrease in the thermodynamically unfavorable contact of the hydrophobic surface clusters with water, alpha-chymotrypsin (CT) was acylated with carboxylic acid anhydrides or re-ductively alkylated with aliphatic aldehydes. Modification of CT with hydrophilic reagents leads to 100-1000-fold increase in stability against the irreversible thermoinactivation. The correlation holds: the greater the hydrophilization increment brought about by the modification, the higher is the protein thermostability. After some limiting value, however, a further increase in hydrophilicity does not change thermostability.It follows from the dependence of the thermoinactivation rate constants on temperature that for hydrophilized CT there is the conformational transition at 55-65 degrees C into an unfolded state in which inactivation is much slower than that of the low-temperature conformation. The thermodynamic analysis and fluorescent spectral data confirm that the slow inactivation of hydrophilized CT at high temperatures proceeds via a chemical mechanism rather than Incorrect refolding operative for both the native and low-temperature form of the modified enzyme. Hence, the hydrophilization stabilizes the unfolded high-temperature conformation by eliminating the incorrect refolding. (c) 1992 John Wiley & Sons, Inc.     

东亚钳蝎粗毒蛋白质热稳定性的研究

目的:通过蝎毒热溶解性和毒性实验,探索蝎毒蛋白稳定性与分子量间的关系。方法:对蝎毒粗毒煮沸后的可溶成分进行急性毒力实验和SDS-PAGE电泳分析。结果:蝎毒粗毒加热处理组的LD50为16.228mg/kg,粗毒对照组的LD50为3.66mg/kg,显示蝎毒经加热后毒力明显降低,但仍具有一定的毒性。SDS-PAGE结果显示,经加热处理的粗蝎毒之沉淀主要为大分子蛋白质,在可溶成分中含有小分子肽类。结论:蝎毒的大分子蛋白质热稳定性差,而小分子多肽部分耐热性强,而且蝎毒的小分子多肽组分具有相对稳定的毒性。     

Effect of magnesium ions on the thermal stability of human poly(A)-specific ribonuclease

Poly(A)-specific ribonuclease (PARN), a member of the DEDD family, is a key enzyme involved in the deadenylation of mRNA in higher eukaryotic cells. In this research, it was found that Mg(2+) could protect PARN against thermal inactivation by increasing the midpoint of inactivation and decreasing the inactivation rate. This protective effect was unique to Mg(2+) in a concentration-dependent manner. However, the thermal unfolding and aggregation was promoted by the addition of Mg(2+) at high temperatures. These results revealed that Mg(2+) might have dual effects on PARN stability: protecting the active site but endangering the overall structural stability.     

Thermal sensitivity of metabolic enzymes in subarctic and temperate freshwater mussels (Bivalvia: Unionoida)

Temperature has a major impact on the physiological processes of freshwater invertebrates. Despite the endangered status of many freshwater mussel species and the potential effect of global warming on North America’s northern aquatic habitats, thermal sensitivity of the metabolic apparatus of freshwater bivalves has received little attention. By examining the thermal sensitivity of 10 key metabolic enzymes and in situ growth rates of latitudinally separated populations (temperate and subarctic) of two closely-related Pyganodon species from northeastern North America, we provide the first insights into thermal sensitivity of key enzymes of energy and reactive oxygen species metabolism in relation to habitat localization and growth performance. The subarctic population of Pyganodon grandis displayed higher in situ growth rates than the temperate population of Pyganodon fragilis. The subarctic population of P. grandis had a lower mitochondrial capacity as expressed by citrate synthase and cytochrome c oxidase but displayed similar electron transport system (ETS) and higher isocitrate dehydrogenase capacities. Our results suggest that higher growth performance of the subarctic population of P. grandis is not associated with higher aerobic capacity. The high thermal sensitivity of mitochondrial enzymes in subarctic population of P. grandis might rather reflect enhanced stenothermy. The higher electron transport system/cytochrome c oxidase ratio for the subarctic P. grandis species than P. fragilis might affect mitochondrial regulation or reactive oxygen species production. Antioxidant enzymes displayed lower Q₁₀s suggesting thermal independence of antioxidant capacity.