Teff, an Orphan Cereal in the Chloridoideae, Provides Insights into the Evolution of Storage Proteins in Grasses

The role of omics in improving the orphan crop tef

Tef or teff [Eragrostis tef (Zucc.) Trotter] is a cereal crop indigenous to the Horn of Africa, where it is a staple food for a large population. The popularity of tef arises from its resilience to environmental stresses and its nutritional value. For many years, tef has been considered an orphan crop, but recent research initiatives from across the globe are helping to unravel its undisclosed potential. Advanced omics tools and techniques have been directed toward the exploration of tef's diversity with the aim of increasing its productivity. In this review, we report on the most recent advances in tef omics that brought the crop into the spotlight of international research.

Microwave radiation induces modifications in the protein fractions of tef flours and modulates their derived techno-functional properties

The impact of microwave (MW) treatments on the structure, solubility, and techno-functional properties of the proteins in starchy matrices is still poorly understood. This study aimed to investigate the effects of MW intensity by applying 1, 2, and 6 min of radiation on two tef flour varieties moistened at 15 % and 25 %. The fractionation method recovered ∼83 % of the total protein content in untreated flours. The interaction between treatment time and moisture content (MC) significantly influenced the extraction of protein fractions. Samples treated at 25 %MC showed significant reductions in albumins (up to -74 %), globulins (up to -79 %), and prolamins (up to -32 %). The SDS-extractable proteins of both tef flours presented similar molecular weights (12-100 kDa). SDS-PAGE analysis revealed decreased band intensity in MW-treated samples compared to untreated flours, and confocal analysis showed changes in the native state of proteins in treated samples. Shorter treatments at low MC significantly improved the emulsifying stability of tef flours, particularly in brown tef flour, with an enhancement of up to 203 %. The hydration properties significantly increased in flours treated at 25 %MC for 6 min. Pearson correlation analysis demonstrated the influence of treatment time and MC on protein recovery and functional properties of tef flours.

Effects of Fungi-Mediated Solid-State Fermentation on Phenolic Contents and Antioxidant Activity of Brown and White Teff (Eragrostis tef (Zucc.) Trotter) Grains

Teff (Eragrostis tef (Zucc.) Trotter) is a tropical cereal used in preparing a staple food in Ethiopia and Eritrea called injera. Phenolic compounds are available in soluble and bound forms in cereals like teff. Therefore, their bioaccessibility depends on their release from the food matrix. Different food processing methods including fermentation have been applied since ancient times to aid bioaccessibility and improve the properties of food products. This study aimed at investigating changes in phenolic profiles and antioxidant activities of white and brown teff grains during mushroom-mediated solid-state fermentation. Fermentation with mushroom considerably increased total phenol contents of the soluble phenol fraction with Ganoderma lucidum showing relatively higher increase than Pleurotus ostreatus. Bound fraction of teff phenol did not show noticeable changes after fermentation with the two mushroom strains. Such changes are suggested to be attributed to activities of fungal enzymes such as amylases, xylanases, and proteases that induce structural breakdown of grain components including cell walls leading to the liberation or synthesis of a variety of phenolic compounds. On the other hand, total flavonoid content of teff significantly decreased after fermentation by both strains. This is also believed to be caused by the action of fungal polyphenol oxidases that catalyze the oxidation of a variety of phenolic compounds including flavonoids to o-quinones.

Isolation and Characterization of Probiotic LAB from Kimchi and Spontaneously Fermented Teff (Eragrostis tef (Zucc.) Trotter) Batter: Their Effects on Phenolic Content of Teff during Fermentation

Microbial fermentation is proven to induce molecular transformations and produce bioactive compounds thereby enhancing sensory and nutritional quality of flour-based fermented foods. In this study, lactic acid bacteria (LAB) were isolated from Korean kimchi and Ethiopian fermented teff (Eragrostis tef (Zucc.) Trotter) flour batter. Isolates were identified using 16S rRNA gene sequencing and characterized for various probiotic properties. Few trains were selected for further teff flour batter fermentation and evaluating their effects on phenolic contents and compositions. Out of 200 bacterial isolates, 44 of them showed considerable acid and bile tolerance and 22 were tested positive for protease activity. A large number of the isolates showed antimicrobial activities against Salmonella gallinarium indicator strains. Majority of these probiotic strains belonged to Lactobacillus plantarum and Lactobacillus brevis species. All the strains used for fermentation of teff were able to significantly increase total phenolic contents (TPC). An increase in TPC of up to 7-fold was observed in some strains.

Towards coeliac-safe bread

Gluten-free foods cannot substitute for products made from wheat flour. When wheat products are digested, the remaining peptides can trigger an autoimmune disease in 1% of the North American and European population, called coeliac disease. Because wheat proteins are encoded by a large gene family, it has been impossible to use conventional breeding to select wheat varieties that are coeliac-safe. However, one can test the properties of protein variants by expressing single genes in coeliac-safe cereals like maize. One source of protein that can be considered as coeliac-safe and has bread-making properties is teff (Eragrostis tef), a grain consumed in Ethiopia. Here, we show that teff α-globulin3 (Etglo3) forms storage vacuoles in maize that are morphologically similar to those of wheat. Using transmission electron microscopy, immunogold labelling shows that Etglo3 is almost exclusively deposited in the storage vacuole as electron-dense aggregates. Of maize seed storage proteins, 27-kDa γ-zein is co-deposited with Etglo3. Etglo3 polymerizes via intermolecular disulphide bonds in maize, similar to wheat HMW glutenins under non-reducing conditions. Crossing maize Etglo3 transgenic lines with α-, β- and γ-zein RNA interference (RNAi) lines reveals that Etglo3 accumulation is only dramatically reduced in γ-zein RNAi background. This suggests that Etglo3 and 27-kDa γ-zein together cause storage vacuole formation and behave similar to the interactions of glutenins and gliadins in wheat. Therefore, expression of teff α-globulins in maize presents a major step in the development of a coeliac-safe grain with bread-making properties.

Exceptional subgenome stability and functional divergence in the allotetraploid Ethiopian cereal teff

Teff (Eragrostis tef) is a cornerstone of food security in the Horn of Africa, where it is prized for stress resilience, grain nutrition, and market value. Here, we report a chromosome-scale assembly of allotetraploid teff (variety Dabbi) and patterns of subgenome dynamics. The teff genome contains two complete sets of homoeologous chromosomes, with most genes maintaining as syntenic gene pairs. TE analysis allows us to estimate that the teff polyploidy event occurred ~1.1 million years ago (mya) and that the two subgenomes diverged ~5.0 mya. Despite this divergence, we detect no large-scale structural rearrangements, homoeologous exchanges, or biased gene loss, in contrast to many other allopolyploids. The two teff subgenomes have partitioned their ancestral functions based on divergent expression across a diverse expression atlas. Together, these genomic resources will be useful for accelerating breeding of this underutilized grain crop and for fundamental insights into polyploid genome evolution.

Teff is an indigenous cereal critical to food security in the Horn of Africa. Here, the authors report an improved genome assembly and observe the surprisingly low levels of large-scale structural rearrangement, homoeologous exchanges, or bias gene loss after the formation of this tetraploid species.

Variations in Amino Acid and Protein Profiles in White versus Brown Teff (Eragrostis Tef) Seeds, and Effect of Extraction Methods on Protein Yields

Data on variations in amino acid compositions and protein profiles among white and brown teff, a grain of growing interest, is either limited or contradicting at the moment. In this study, three white (Addis-W, Mekel-W and Debre-W) and three brown (Addis-B, Mekel-B and Debre-B) teff seed samples were used for whole flour amino acid analysis and protein fractionation with three different methods. White and brown seed types showed different physical changes during protein extraction. Brown teff displayed higher essential amino acid content than white with lysine present in high concentration in both seed types. Extraction with tert-butanol increased prolamin yields in teff compared to ethanol. The major protein fraction in teff was glutelin with white teff containing higher glutelin proportion than brown. Sodium Dodecyl Sulfate Gel Electrophoresis (SDS-PAGE) analysis revealed clear genetic variability between white and brown teff seed types.