The inheritance of β-amylases in developing barley grain

Three types of -amylase isozyme pattern (Sd^d, Sd^e, and Sd^f) were observed in the doughy endosperm stage of ripening barley grains. From crosses between Sd^d and Sd^f types, it was concluded that these phenotypes are controlled by a pair of codominant alleles. Preliminary studies on the distribution of these -amylase zymotypes indicated that this polymorphism in developing grain is related to a -amylase polymorphism in barley malt.     

Interspecific hybridization in the grain legumes—a review

The current position regarding reports in the literature on interspecific hybridization in the pulses is confused. Two major reasons can he advanced in explanation. The first is that frequently conspecific wild and cultivated forms have received different binomials and crosses between such are frequently regarded as interspecific hybrids. The second arises from mistaken interpretation of results of attempted interspecific hybridization when progeny strongly resembling the maternal parent are produced. It is suggested that these progeny might have been produced by failures in emasculation or rare accidental apomixis. All cultigens of the generaArachis, Cajanus, Cicer, Phaseolus andPisum are able to some extent to produce viable true interspecific hybrids as are the Asiatic forms ofVigna. True interspecific hybrids have not been produced withVicia faba nor withVigna unguiculata the cowpea.     

A hemicellulosic β-D-glucan from the endosperm of sorghum grain

A hemicellulosic β-D-glucan of $\text{d.p.}$ ≈26 has been isolated from the endosperm of sorghum grain. Methylation analysis, partial hydrolysis with acid, and periodateoxidation studies showed that the glucan is linear and has both (1 → 3)- and (1 → 4)-linked D-glucopyranose residues in the ratio of 3:2. The low, positive, specific rotation and chromium trioxide oxidation studies indicated that the D-glucose residues are β-linked.     

Phenol oxidising enzymes in the grain aphid’s saliva

Sucrose-agarose gels and sucrose liquid diets were used to study the phenol oxidising enzymes in the salivary secretions of the grain aphid, Sitobion avenae (Fabricius). Activity indicating the presence of two oxidoreductases, polyphenol oxidase (PPO) and peroxidase (Px), was found. Both enzymes were present in the aphids stylet sheath (gelling saliva) but only polyphenol oxidase activity was found in the halos around sheaths and thus in watery saliva. Electrical penetration graphs (EPG) revealed that the secretion of these enzymes into the gels, by an individual aphid, was associated with its probing activity observed during penetration of the epidermal and mesophyll tissues. The grain aphids PPO, secreted in its saliva reacted with a range of phenolic compounds. As most of these phenolics occur naturally in cereals, the grain aphid could modify its host-plants phenolic composition. The importance of the grain aphids polyphenol oxidase and peroxidase in detoxifying cereal phenolics is discussed.     

Bifunctional inhibitor of α-amylase/trypsin from wheat grain

A trypsin inhibitor, isolated from whole-wheat grain (Triticum aestivum L.) by the method of biospecific chromatography on trypsin-Sepharose, was potent in inhibiting human salivary α-amylase. The bifunctional α-amylase/trypsin inhibitor was characterized by a narrow specificity for other α-amylases and proteinases. The high thermostability of the inhibitor was lost in the presence of SH group-reducing agents. The inhibitor-trypsin complex retained its activity against α-amylase. The inhibitor—α-amylase complex was active against trypsin. Studies of the enzyme kinetics demonstrated that the inhibition of α-amylase and trypsin was noncompetitive. Our results suggest the existence of two independent active sites responsible for the interaction with the enzymes.     

TaTPP-7A positively feedback regulates grain filling and wheat grain yield through T6P-SnRK1 signalling pathway and sugar–ABA interaction

Grain size and filling are two key determinants of grain thousand-kernel weight (TKW) and crop yield, therefore they have undergone strong selection since cereal was domesticated. Genetic dissection of the two traits will improve yield potential in crops. A quantitative trait locus significantly associated with wheat grain TKW was detected on chromosome 7AS flanked by a simple sequence repeat marker of Wmc17 in Chinese wheat 262 mini-core collection by genome-wide association study. Combined with the bulked segregant RNA-sequencing (BSR-seq) analysis of an F₂ genetic segregation population with extremely different TKW traits, a candidate trehalose-6-phosphate phosphatase gene located at 135.0 Mb (CS V1.0), designated as TaTPP-7A, was identified. This gene was specifically expressed in developing grains and strongly influenced grain filling and size. Overexpression (OE) of TaTPP-7A in wheat enhanced grain TKW and wheat yield greatly. Detailed analysis revealed that OE of TaTPP-7A significantly increased the expression levels of starch synthesis- and senescence-related genes involved in abscisic acid (ABA) and ethylene pathways. Moreover, most of the sucrose metabolism and starch regulation-related genes were potentially regulated by SnRK1. In addition, TaTPP-7A is a crucial domestication- and breeding-targeted gene and it feedback regulates sucrose lysis, flux, and utilization in the grain endosperm mainly through the T6P-SnRK1 pathway and sugar–ABA interaction. Thus, we confirmed the T6P signalling pathway as the central regulatory system for sucrose allocation and source–sink interactions in wheat grains and propose that the trehalose pathway components have great potential to increase yields in cereal crops.     

Bioactivities of extracts from Acorus gramineus on four stored grain pests

1 INTRODUCTIONControl of the stored product insects around theworldis primarily dependent upon insecticides such asorganophosphates and pyrethroids , and gaseousinsecticides such as methyl bromide and phosphine .Although effective ,their repeated use for …     

The mineral composition of the tests of ‘testate amoebae’ (Amoebozoa,Arcellinida): The relative importance of grain availability and grain selection

Nine peatlands were selected according to their various geological setting in the eastern part of France. The diversity of mineral particles, including xenosomes (agglutinated particles) and idiosomes (secreted particles), were analysed, together with associated morphological characteristics, for 7 species of ‘testate amoeba’ (order Arcellinida). The combined use of an Environmental Scanning Electron Microscope equipped with an EDS device and microprobe analyses is suitable for conducting an elemental analysis and subsequently enabled the determination of 24 different minerals. Such mineral diversity has never been recorded before. We conclude that the testate amoebae select grains according to their size from those available within their immediate environment. Availability in turn reflects the geological surroundings and the stability of the different kinds of grains, while their size seems to be a function of the distance from the source.     

Internodes of grain legumes — New location for xylem parenchyma transfer cells

Summary Xylem parenchyma transfer cells were observed in the primary and secondary vascular tissue of stem internodes of 21 in 28 species of grain legumes. Their structural features were similar to those of other transfer cells. The relationships of these cells to transfer cells at nodes were investigated. Non-nodulated seedlings ofPhaseolus vulgaris L. formed internode transfer cells if provided mineral nutrients through their roots, but not if grown in distilled water or fed nutrients entirely through their leaves. Wall ingrowths formed in parenchyma of primary xylem ofPhaseolus just before full extension of an internode. The significance of this new location for transfer cells was discussed.     

Is nitrogen accumulation in grain legumes responsive to growth or ontogeny?

Nitrogen (N) accumulation in legumes is one of the main determinants of crop yield. Although N accumulation from symbiotic nitrogen fixation or N absorption from the soil has been widely investigated, there is no clear consensus on timing of the beginning of N accumulation and the termination of N accumulation and the physiological events that may be associated with these two events. The analyses conducted in this study aimed at identifying the determinant of N accumulation in two grain legume species. Nitrogen accumulation dynamics and mass accumulation and development stages were recorded in the field for several genotypes of common bean (Phaseolus vulgaris) and faba bean (Vicia faba) under different growing conditions. This study showed that during the vegetative stages, N accumulation rate was correlated with mass accumulation rate. However, the maximum accumulation of N did not correspond to the time of the maximum mass accumulation. In fact, for both species, N accumulation was found to persist in seed growth. This challenges a common hypothesis that seed growth causes a decrease in N accumulation because of a shift of the photosynthate supply to support the seed growth. Even more surprising was the shift of the active accumulation of N in faba bean to late in the growing season as compared with common bean. N accumulation by faba bean only was initiated at high rates very late in vegetative growth and persisted at high rates well into seed fill.     

Hydrogen sulfide stimulates β-amylase activity during early stages of wheat grain germination

We recently reported that H₂S could significantly promote the germination of wheat grains subjected to aluminum (Al³⁺) stress.¹ In these experiments seeds were pretreated with the H₂S donor NaHS for 12 h prior to Al³⁺ stress. During this pre-incubation period we observed that H₂S increased the activity of grain amylase in the absence of Al³⁺. Using embryoless half grains of wheat we now show that H₂S preferentially affects the activity of endosperm β-amylase and that α-amylase synthesis and activity is unaffected by this treatment.Key words: α-amylase, β-amylase, hydrogen sulfide, reactive sulfur species, seed germination, wheat (triticum)Cereal grains contain many acid hydrolases, some synthesized de novo by the scutellum and aleurone layer and others are found preformed in the starchy endosperm. The amylases are the best known of these types of enzymes. α-Amylases are synthesized and secreted by the scutellum and aleurone layer, and in the case of aleurone isoforms their synthesis is regulated by GAs and ABA.^2,3 Whereas GAs stimulate the synthesis of α-amylases and many other secreted hydrolases, ABA inhibits these processes. β-Amylases, on the other hand, are preformed enzymes whose synthesis is not affected by ABA and GAs. Two forms of β-amylase are found in wheat grains, one is a soluble form present in ungerminated grains which can form high-molecular-weight homopolymers or heteropolymers; the other is bound in an inactive form via S-S linkages to proteins at the periphery of starch grains.^4,5 The activation of β-amylases is thought to result at least in part from their release from endosperm proteins by the action of GA-induced proteases secreted from the aleurone layer.⁶To examine in more detail the effect of H₂S on wheat grain amylases we used de-embryontated wheat grains where only the aleurone layer and starchy endosperm were the possible sources of amylase activity. Embryoless half grains of wheat (Triticum aestivum L., c.v Yangmai 158) were incubated in water, the H₂S donor NaHS, GA, or combinations of these treatments for up to 12 h. After incubation soluble proteins were isolated from grains by homogenizing in buffer and amylase activity was determined colorimetrically using starch-I₂KI. Figure 1A shows that during the first 8 h of incubation there was no increase in amylase activity from half grains incubated in H₂O or GA but there was a small but significant increase in activity after 10 h and 12 h of incubation in these two treatments. By contrast, incubation in NaHS brought about a three-fold increase in amylase activity by six h and this increased to about five-fold above the initial activity by 12 h of incubation.Open in a separate windowFigure 1Amylolytic activity from wheat half grains measured colorimetrically (A), by diffusion into agar-starch (B) and following native gel electrophoresis (C and D). (A) Half grains were incubated in water (CK), 0.5 mM NaHS, 10 µM GA3 and 0.5 mM NaHS plus 10 µM GA3 for up to 12 h. Amylase activity was measured colorimetrically on grain homogenates by the starch I-KI method. (B) Half grains pre-incubated as (A) then transferred to agar containing 0.2% starch and 2 mM EDT A for a further 12 h. Amylolytic activity was determined by the diameter of the starch-free halo after flooding the agar-starch plate with I-KI solution. Seeds treated with CK, NaHS, GA₃ and NaHS plus GA₃ were lined from left to right in each plate, respectively. (C and D) Wheat grains incubated for 12 h in H₂O, NaHS, GA₃ and Hb (0.1 g/L) and combinations of these treatments, were homogenized and aliquots of extracts were electrophoresed by non-denaturing PAGE. After electrophoesis gels were soaked in starch, washed and stained with I-KI. Amylolytic activity is shown by cleared areas in the gel. For the gel in (C), homogentes were incubated with 25 mM EDT A to inactivate α-amylase and for (D), they were heated at 70°C to inactivate β-amylase.We confirmed these results by incubating wheat half gains on 0.2% agar containing 0.2% soluble starch and 2 mM EDTA (Fig. 1B). In this experiment, half grains were first incubated in H₂O, GA or NAHS for up to 12 h as for the experiment shown in Figure 1A and half grains were transferred to agar to estimate amylase activity. Because α-amylases are Ca²⁺-containing metalloenzymes whose activities are dependent on Ca²⁺ binding we incorporated EDTA into the agar to favor the appearance of β-amylase activity. The data in Figure 1B confirm what we observed when we measured amylase activity colorimetrically, namely that starch degrading activity was high in half grains exposed to NaHS but low in those incubated in H₂O or GA. From this experiment we also concluded that the starch degrading activity was likely a result of the activity of β-amylase as α-amylase activity would have been reduced or eliminated by the presence of EDTA.We established that the amylolytic activity produced by wheat grains in response to the NaHS donor was largely β-amylase by selectively inhibiting amylase activities following native gel electrophoresis. α-Amylases are heat stable but are sensitive to metal chelators, whereas β-amylases are denatured by heating but are not inhibited by chelators such as EDTA.⁴ Figure 1C and D show the activities of amylase isoforms measured by incubating non-denaturing polyacrylamide gels in 1% soluble starch followed by staining in I-KI. Figure 1C shows amylolytic activity after incubation of the gel in starch containing 25 mM EDTA. Two distinct sets of bands are seen together with minor bands of activity. Whereas group I amylases do not change significantly following treatment incubation in the presence of NaHS or GA, group II amylases show high activity in the presence of NaHS, but show no activity with GA (Fig. 1C). When the enzyme preparations were heated to 70°C for 15 min before electrophoresis almost all activity was lost showing that the activity seen in the absence of heating but in the presence of EDTA was likely that of β-amylase. We also used hemoglobin (Hb) a nonspecific H₂S scavenger to show that the effects of NaHS were indeed via the production of H₂S. Figure 1C shows that Hb almost completely abolished the inductive effect of NaHS on β-amylase activity.Although at present we have no direct evidence that H₂S acts as an endogenous regulator of endosperm function in cereal grains, it is tempting to speculate that this is indeed the case. Our previous work showed an increase in the synthesis of H₂S by wheat grains that is detected as early as 12 h following the start of imbibition in H₂O.¹ Although we have no information on the route of H₂S synthesis in wheat, there is abundant evidence that plants synthesize H₂S as its emission has been observed in many species.^7–13 In plants, H₂S is thought to be released from cysteine via a reversible O-acetylserine (thiol) lyase (OASTL) reaction, and recently several L- and D-cysteine-specific desulfhydrase candidates have been isolated and partially characterized from Arabidopsis thaliana, confirming H₂S release by the action of desulfhydrases in various cellular compartments.^14–17 The induction of L-cysteine desulfhydrase upon pathogen attack,¹⁸ freezing tolerance by H₂S fumigation,¹⁹ emission of H₂S from plants exposed to SO₂ injury,^10,20 and abiotic stresses tolerance in plants treated with H₂S donor,^1,21–24 all infer that H₂S is involved in these responses.It is also tempting to speculate that H₂S may work in cereal grains by influencing redox status.^15,25 It has been proposed that H₂S can bring about an increase in synthesis of glutathione from cysteine and an overall improvement of plant performance under stress. The release of β-amylase from starchy endosperm proteins or the dissociation of free β-amylase from small homopolymers or heteropolymers has been shown to be enhanced by reducing agents such as dithiothreitol and by S-H proteinases. We propose that one plausible action of H₂S in cereal endosperm is to enhance reactive sulfur species that can lead to reduction of S-S bonds between β-amylase and its binding partners in the endosperm. Release of activated β-amylase would then be free to participate in starch degradation providing sugar units for seedling growth and development prior to the induction of α-amylases by GAs.     

Spirit-based distillers’ grain as a promising raw material for succinic acid production

Spirit-based distillers’ grain (SDG) is the main by-product of the Chinese liquor industry, with an annual output of approx. 100 million tons. The economical potential of fermentative production of succinic acid from SDG was investigated using Actinobacillus succinogens. Use of pretreated SDG (PSDG) as the sole source of C and N yielded succinic acid at 35.5 g l^?1 with a yield of 19.7 % (g per 100 g PSDG) after 48 h in a 3 l stirred bioreactor. SDG is thus a promising feedstock for the economical production of succinic acid.     

Temporal dynamics in wheat grain zinc distribution: is sink limitation the key?

Background and Aims

Enhancing the zinc (Zn) concentration in wheat (Triticum aestivum) grain is a breeding objective in order to improve human Zn nutrition. At enhanced plant Zn uptake, grain Zn levels do not increase proportionally and within the grain the endosperm Zn levels remain below grain Zn levels. This study analysed the temporal dynamics of Zn concentrations in grain tissues during grain filling to find major bottlenecks.

Methods

Plants of two cultivars were grown at 1 and 5 mg Zn kg⁻¹ soil. Individual panicles were harvested 7, 14, 24 or 34 d after their flowering or at maturity and seeds were dissected into constituting tissues, which were analysed for Zn and other minerals.

Key Results

The Zn concentration of the crease was found to increase five- to nine-fold between 7 and 34 d after anthesis, while that of the endosperm decreased by 7 and 45 % when grown at 1 or 5 mg Zn kg⁻¹, respectively. The Zn turnover rate (d⁻¹) in the crease tissues was either independent of the Zn application level or higher at the lower Zn application level, and the Zn concentration increased in the crease tissues with time during grain filling while the turnover rate gradually decreased.

Conclusions

There is significant within-seed control over Zn entering the seed endosperm. While the seed crease Zn concentration can be raised to very high levels by increasing external Zn supply, the endosperm Zn concentrations will not increase correspondingly. The limited transfer of Zn beyond the crease requires more research to provide further insight into the rate-determining processes and their location along the pathway from crease to the deeper endosperm     

Contribution à l'analyse des structures forestières 1. Le grain des dominances

A method of simultaneous analysis of vertical and horizontal structure is described. It is particulary applicable to forest and shrubland. Data come from point-height analysis of vegetation: 100 sample points are arranged in 4 lines of 25, with 2 m between lines and 1 m between points on lines. At each point, specific lists of spaces intercepted optically are observed by vertical measurement strata. Strata depth is 10 cm when mean vegetation height is lower than 4–5 m, and 50 cm above this height. This study is based on height of upper vegetation presence, and applied to low forests ofNothofagus antarctica (Forest.)Verst. in Southern Chile and Argentina. The authors summarize the data sequence by the cumulative sum technique. This technique allows the rapid and clear delimitation of three dimensional mosaic units of vegetation whose height varies vertically from the mean height. The pattern of these mosaic units is shown as three dimensional block diagrams, giving a good representation of structural dominance patterns.     

Effect of environment on multi-element grain composition of pigeonpea cultivars under farmers’ conditions

Pigeonpea (Cajanus cajan L. Millsp.) is often intercropped with maize (Zea mays L.) in eastern and southern Africa. The studies aimed at determining how different genotypes of pigeonpea responded in terms of grain element composition under farmers’ cropping conditions. Approx. 78 farmers participated. They came from four study sites in Tanzania (Babati and Gairo) and Malawi (Nyambi and Ntonda) that differed in terms of tradition for using pigeonpea as well as in environmental conditions. The individual grain weight of the pigeonpea crops from Malawi were 21% (P < 0.05) higher than those from Tanzania. However, only B, Cu, Mo, N, Ni, P and S were affected by grain weight (P < 0.05). Weak (r ² < 0.10) negative correlations existed between grain yield and the grains’ proportion of Ca, Mg, P, and Zn. The proportion of every element, with the exception of Cr, in the grain differed between sites (P < 0.05) but not between varieties (P > 0.05). The amounts of K, Mg, S and Fe accumulated per grain were slightly lower (P < 0.11) in ICEAP00040 compared to the more traditional varieties. Variations in DTPA-exchangeable Zn and Fe in the soil were not reflected in grain concentrations but grain P had a curvi-linear relation (r ² = 0.44) to the soil NaHCO₃^–-exchangeable P indicating P deficiency for several soils. The P and Zn content were correlated (r ² > 0.41) as the only two grain elements. Unique fingerprinting by multivariate statistics was possible for each site when using the element proportion of the grain dry matter with or without soil characteristics. In all cases, different elements contributed with varying weight to the discrimination between the sites. However, it was not possible to distinguish between the varieties when considering all four environments. Reducing the models to include Fe, K, Mg, P, S and Zn only, did however allow some distinction between the two genotypes, which indicates that genotypic variability is expressed in a fairly limited number of elements. In the cases of Gairo and Nyambi, it was possible to distinguish between varieties. In the case of Gairo, the models distinguished between ICEAP00068 and the others, i.e. ICEAP00040 and Babati White where ICEAP00068 was associated with a higher proportion of Fe, P, S, and Zn in the grain. In the case of Nyambi, the models distinguished between ICEAP00040 and ICP9145 where ICEAP00040 was associated with a lower proportion of Ca, Cu, Fe, Mn, Ni, P, S, and Zn and a higher proportion of Cr and Na in the grain. It is thus possible in some cases to separate varieties based on multi-element grain content across a relatively narrow environmental gradient but not generally across all environments. These findings should be included in breeding programmes focusing on the improvement of the nutritional value of our food crops.     

Wheat grain yield on saline soils is improved by an ancestral Na⁺ transporter gene

The ability of wheat to maintain a low sodium concentration ([Na(+)]) in leaves correlates with improved growth under saline conditions. This trait, termed Na(+) exclusion, contributes to the greater salt tolerance of bread wheat relative to durum wheat. To improve the salt tolerance of durum wheat, we explored natural diversity in shoot Na(+) exclusion within ancestral wheat germplasm. Previously, we showed that crossing of Nax2, a gene locus in the wheat relative Triticum monococcum into a commercial durum wheat (Triticum turgidum ssp. durum var. Tamaroi) reduced its leaf [Na(+)] (ref. 5). Here we show that a gene in the Nax2 locus, TmHKT1;5-A, encodes a Na(+)-selective transporter located on the plasma membrane of root cells surrounding xylem vessels, which is therefore ideally localized to withdraw Na(+) from the xylem and reduce transport of Na(+) to leaves. Field trials on saline soils demonstrate that the presence of TmHKT1;5-A significantly reduces leaf [Na(+)] and increases durum wheat grain yield by 25% compared to near-isogenic lines without the Nax2 locus.     

Genetic basis of grain yield heterosis in an “immortalized F2” maize population

Key message

Genetic basis of grain yield heterosis relies on the cumulative effects of dominance, overdominance, and epistasis in maize hybrid Yuyu22.

Abstract

Heterosis, i.e., when F₁ hybrid phenotypes are superior to those of the parents, continues to play a critical role in boosting global grain yield. Notwithstanding our limited insight into the genetic and molecular basis of heterosis, it has been exploited extensively using different breeding approaches. In this study, we investigated the genetic underpinnings of grain yield and its components using “immortalized F₂” and recombinant inbred line populations derived from the elite hybrid Yuyu22. A high-density linkage map consisting of 3,184 bins was used to assess (1) the additive and additive-by-additive effects determined using recombinant inbred lines; (2) the dominance and dominance-by-dominance effects from a mid-parent heterosis dataset; and (3) the various genetic effects in the “immortalized F₂” population. Compared with a low-density simple sequence repeat map, the bin map identified more quantitative trait loci, with higher LOD scores and better accuracy of detecting quantitative trait loci. The bin map showed that, among all traits, dominance was more important to heterosis than other genetic effects. The importance of overdominance/pseudo-overdominance was proportional to the amount of heterosis. In addition, epistasis contributed to heterosis as well. Phenotypic variances explained by the QTLs detected were close to the broad-sense heritabilities of the observed traits. Comparison of the analyzed results obtained for the “immortalized F₂” population with those for the mid-parent heterosis dataset indicated identical genetic modes of action for mid-parent heterosis and grain yield performance of the hybrid.