Significant down-regulation of γ-gliadins has minor effect on gluten and starch properties of bread wheat

The contribution of gliadins to the baking performance of wheat has been widely discussed. In the present study we report the properties of the flours of fifteen transgenic wheat lines with γ-gliadins down-regulated by RNAi. Technological properties were assessed by sodium dodecyl sulfate sedimentation (SDSS) test, and rheological properties were characterized during mixing using the Mixolab^®. Changes in the proportions of gluten proteins, with significant increases of glutenins, were observed in transgenic lines. These changes did not affect the SDSS test in most of the transgenic lines. The dough strength of some transgenic lines was reduced as determined by the Mixolab^®. Changes in the starch behavior were also observed in the transgenic lines, in which lower values of torque were observed at the C3, C4 and C5 points of the mixing curve. The results reported here are important in understanding the role of γ-gliadins in the bread-making quality of flours.     

Structure and enzymatic resistivity of debranched high temperature–pressure treated high-amylose corn starch

High-amylose corn starch (HACS) was treated with high temperature–pressure (HTP) treatment and pullulanase debranching. It was found that 24 h storage was favorable for resistant starch (RS) formation. Structure (granular morphology, fractal structure, lamellar structure, crystalline structure, weight-average molecular weight) and properties (swelling power, solubility, enzymatic resistivity) were evaluated for native starch and the samples with 24 h storage. By modification, the surface became loose and rough fragmented and the birefringence crosses disappeared. All samples displayed a B + V crystalline structure. The scattering objects of native starch at the higher scale level were more compact than those of modified starches, and the latter displayed a mass fractal structure which became more compact as debranching increased. The native starch contained RS2 and RS5, while the modified samples included RS3 and RS5. The higher amount of V-type crystals and the starch chains with smaller molecular weight could lead to form more RS. Interestingly, a surface fractal structure with D_s2 was measured for the modified starches, leading to more RS, since some active sites of starch molecules were masked by the ordered-aggregations of molecular chains in the scattering objects. Furthermore, the more compact scattering objects with D_m1 contributed to forming more RS.     

Substrate selectivity and inhibitor sensitivity affect xylanase functionality in wheat flour gluten–starch separation

Addition of xylanases (EC 3.2.1.8) that varied in their substrate selectivities and/or wheat xylanase inhibitor sensitivities in dough batter gluten–starch separation of wheat flour showed the importance of these enzyme characteristics for their functionality in this process. A xylanase from Aspergillus aculeatus (XAA) with selectivity for hydrolysis of water extractable arabinoxylan (WE-AX), which is not inhibited by wheat flour xylanase inhibitors decreased batter viscosity and improved gluten agglomeration behaviour. In contrast, a xylanase from Bacillus subtilis (XBS_i) with selectivity for hydrolysis of water unextractable arabinoxylan (WU-AX), which is in vitro inhibited by wheat flour xylanase inhibitors had a negative effect on gluten agglomeration at low enzyme dosages. As expected, solubilisation of WU-AX increased batter viscosities. At higher dosages however, this enzyme also improved gluten agglomeration because of degradation of both WE-AX and enzymically solubilised AX. A mutated B. subtilis xylanase (XBS_ni) with selectivity for hydrolysis of WU-AX comparable to XBS_i but which is not inhibited by wheat flour xylanase inhibitors, increased the level of large gluten aggregates as well as the total gluten protein recovery, even at lower dosages. Because of its inhibitor insensitivity, the solubilisation and degradation of AX proceeded further. An XBS_ni dosage approximately 4 times lower than XBS_i performed as well as its inhibited counterpart. The degradation of both WE-AX and WU-AX by XBS_ni improved the gluten agglomeration behaviour to a larger extent than the XAA treatment which primarily resulted in hydrolysis of WE-AX. The results confirm the detrimental impact not only of WE-AX, but also of WU-AX, on gluten agglomeration in a dough batter gluten–starch separation process. At the same time, they provide firm evidence that xylanases are not only inhibited by xylanase inhibitors in vitro, but are also partly inhibited in the industrial process in which they are used.     

Suppression of starch accumulation in ‘sugar leaves’ of rice affects plant productivity under field conditions

While many plants accumulate the majority of their photoassmilates as starch during the daytime, some plants accumulate sucrose. Although the existence of these high-sucrose leaves, called ‘sugar leaves’, has long been known, the physiological characteristics of sugar leaves compared to ‘starch leaves’ remain unclear. In this study, the physiological roles of starch accumulation in rice, which has typical sugar leaves, were investigated using a mutant with suppressed leaf-starch biosynthesis. When grown under controlled conditions with light intensity of 400 μmol m^?2 s^?1, the initial growth of the mutant was similar to that of the wild-type plant, even with a 6-h-light/18-h-dark photoperiod in which carbon resources for growth are required during the night. This finding indicates that rice does not rely on leaf starch as a carbon resource during the night. By contrast, under field conditions, the grain yields of the mutant were significantly lower than those of the wild type only when the plants were exposed to full sunlight during the ripening period. These results may indicate that starch accumulation in sugar leaves plays an important role in maintaining a high source capacity under sufficient light conditions rather than as a carbon resource for the plant’s growth at night.     

Effects of selected extrusion parameters on physicochemical properties and in vitro starch digestibility and β-glucan extractability of whole grain oats

Whole grain oat flour was extruded under different moisture contents (15%, 18%, 21%), barrel temperatures (100 °C, 130 °C), and screw speeds (160 rpm, 300 rpm, 450 rpm), and selected physicochemical properties, in vitro starch digestibility, and β-glucan extractability of the extrudates were analyzed. An increase in screw speed resulted in an increase in radial expansion index, water absorption index, and water solubility index. Screw speed significantly affected slowly and rapidly digestible starch. Moderate screw speed (300 rpm) led to higher slowly digestible starch with an accompanying decrease in rapidly digestible starch. Low moisture conditions (15%) resulted in the highest resistant starch and water-extractable β-glucan. Under the conditions used in this study, extrusion did not result in changes in water-extractable β-glucan molecular weight. Thus, extrusion might be beneficial in improving functionality and consumer acceptability by affecting physicochemical properties, in vitro starch digestibility, and β-glucan extractability of oat extrudates.     

Two β-amylase genes,OsBAM2 and OsBAM3, are involved in starch remobilization in rice leaf sheaths

To identify mechanisms of starch degradation in rice leaf sheaths at the post-heading stage, we investigated the function of OsBAM2 and OsBAM3, which encode plastid-targeted active β-amylase isoforms, in starch remobilization in leaf sheaths. The starch content in the second leaf sheaths below the flag leaf (the third leaf sheaths) peaked at the flag leaf emergence stage and gradually decreased until 15 days after heading. The mRNA levels of OsBAM2 and OsBAM3 in the third leaf sheaths increased from the flag leaf emergence stage to the heading stage when the starch content began to decrease. However, these mRNA levels did not always remain high during post-heading. Overexpression of OsBAM2 or OsBAM3 markedly repressed starch accumulation in the third leaf sheaths, showing that OsBAM2 and OsBAM3 function in starch degradation in rice leaf sheaths. In contrast, no significant differences in starch content in the third leaf sheaths were detected between knockdown plants of OsBAM2 or OsBAM3 and non-transgenic wild-type plants. Our results suggest that reduced expression of the individual genes, OsBAM2 or OsBAM3, does not result in excess accumulation of starch in the leaf sheaths, probably because of the complementary function of another gene or the action of other genes encoding starch-degrading .     

Mechanism of gas cell stabilization in bread making. I. The primary gluten–starch matrix

Expansion of dough and hence bread making performance is postulated to depend on a dual mechanism for stabilization of inflating gas bubbles. Two flours were used in this study, one from the wheat variety Jagger (Jagger) and the other from a composite of soft wheat varieties (Soft). Thin liquid lamellae (films), stabilized by adsorbed surface active compounds, act as an auxiliary to the primary gluten–starch matrix in stabilizing expanding gas cells and this mechanism operates when discontinuities begin to appear in the gluten–starch matrix during later proving and early baking stages. Contributions of the liquid lamellae stability to dough expansion were assessed using flours varying in their lipid content. Incremental addition of natural lipids back into defatted flour caused bread volume to decrease, and, after reaching a minimum, to increase. Strain hardening is a key rheological property responsible for stabilizing the primary gluten–starch matrix. Jagger gave higher test-bake loaf volume than Soft and higher strain hardening index for dough. The different lipid treatments were found to have negligible effects on strain hardening index. Image analysis of crumb grain revealed that differences in number of gas cells and average cell elongation with different lipid treatments were insignificant. The evidence agrees with a dual mechanism to stabilize the gas cells in bread dough. To understand dough rheology at a molecular level, rheological properties of doughs were varied by addition of flour protein fractions prepared by pH fractionation. Fractions were characterized by SE-HPLC and MALLS. The molecular weight distribution (MWD) of fractions progressively shifted to higher values as the pH of fractionation decreased. Mixograph dough development time paralleled the MWD. However, the strain hardening index and the test-bake loaf volume increased with increasing MWD up to a point (optimum), after which they declined. At a given strain rate, the behavior at the optimum is thought to result from slippage of the maximum number of statistical segments between entanglements, without disrupting the entangled network of polymeric proteins. Shift of MWD to molecular weight higher than the optimum results in a stronger network with reduced slippage through entanglement nodes, whereas a shift to lower molecular weights will decrease the strength of the network due to a lesser number of entanglements per chain.     

The Development of β-Glucanase and Degradation of β-Glucan in Barley Grown in Scotland and Spain

The barley mutant TR49 and the cultivar from which it was derived, Troubadour, were grown in Scotland and Spain and harvested in 1991 and 1992. The development of β-glucanase together with the breakdown of β-glucan and the reduction in milling energy were followed during malting. While similar amounts of β-glucan were found in samples from both sites, TR49 showed less response to environmental conditions. Grain from Spain showed higher levels of β-glucanase activity, differences being apparent after steeping and 1–2 days of germination. The milling energy of grain was the same, but, during malting, samples from Spain showed a greater reduction in milling energy than those from Scotland. The most extreme environment in the study was the 1991 season at the Spanish site and was the driest and hottest. But even in the cooler, wetter season of 1992, Spanish grown material showed a greater production of β-glucanase than Scottish grown samples. These findings have important implications for plant breeding as well as the growing and trading of malting barley on a European scale.     

Changes in Methamidophos Resistance and Fitness of Hybrids in Different Strains of Nilaparvata lugens

A resistant strain selected successively in the laboratory for 17 generations had 198.63-fold resistance to methamidophos. The resistant levels and fitness of progenies from the resistant strain and susceptible strain or field population were closer to those of the resistant strain than those of the susceptible strain or field population. The changes in the resistant levels of the hybrid were propitious to the resistance development, however, the changes of the fitness went to the contrary. The effects of the migration on the development of methamidophos resistance in Nilaparvata lugens were discussed in the aspects of the migration of Nilaparvata lugens, the resistant levels of progenies and the changes of the fitness.     

Origin and cultivation history of rice in China

According to the documental accounts, the distribution of wild rice (O.perennis), the ancestor species of cultivated rice in ancient China is possibly more northward than in the modern times. The earliest rice grains unearthed from the Neolithic sites existed along the lower and middle reaches of the Yangtze River.     

Correlations between ultrastructure and photosynthesis in leaves of rice and barnyard-grass

The ultrastructure of the leaves of rice(Oryza sativa)and barnyardgrass(Echinochloa crus-galli)in their milking stage were studied withelectron microscopy.The content of chloro-     

AMMI analysis of interaction of genotype and environment in chalkiness of indica rice

Chalkiness is an unpleasant trait for rice con-sumer. which is known to be controlled geneti-cally and affected by environment during grainmaturing. We used the model of Additive MainEffects and Multiplieative Interaction (AMMI)for interpreting the result of genotype by env-iornment interaction (G×E) in the chalkinessof indica rice varieties.     

Effects of environment and variety on content and molecular weight of β-glucan in oats

Oat β-glucan has been shown to have cholesterol, insulin and glucose lowering effects, which are related to increased viscosity of the intestinal contents. Some important factors influencing the viscosity are molecular weight, structure and concentration. To study the effect of variety and environment on β-glucan content and molecular weight of β-glucan, four oat varieties were grown in 11 different environments (location × year combinations) in a field experiment. The β-glucan content varied between 2.3 and 3.2% and the average molecular weight of β-glucan between 1.73 and 2.02 × 10⁶ g mol⁻¹. There was a significant difference between varieties and environments for both β-glucan content and molecular weight of β-glucan. The effect of environment was much greater on molecular weight (71%) than on β-glucan content (42%), while the effect of variety was greater on β-glucan content (23%) than on molecular weight (4%). There was also a positive significant correlation between β-glucan content and molecular weight of β-glucan (p < 0.001, r = 0.46). These results show that β-glucan content is a better target for plant breeding than molecular weight. However, both factors are important for the physiological effects of β-glucan, and selection for high β-glucan content will probably also give higher molecular weight.     

Combined pollution of Cd and Zn in soil-rice systems and its indexes

Due to the mining, smelting, sewage irrigation, agricultural runoff, and development of rural enterprises, combined pollution of Cd and Zn in soil-rice systems has frequently oceurred. This problem was studied by using the pot-culture imitative method combined with heroical analysis and mathematical models. Tested soil was brunisolic paddy soil and the tested concentrations of Cd and Zn were selected as follows: Cd (mg/kg) 0.0 0.5 1.0 1.5 2.0 3.0 Zn (mg/kg) 0.0 100 200 400 The results showed that the Cd-Zn combined pollution was more complicated than the single-factor pollution of Cd or Zn in soil-rice system: Influences of the Cd-Zn combined pollution on biological yield of rice, accumulation and distribution on Cd and Zn in tissues of rice were not only dependent on the concentration of Cd and Zn added into the tested paddy soil, but also related to their ratio. Under the condition of the Cd-Zn combined pollution, interrelationship between biological yield (Y) of rice and exponential logarithmic value     

Biological characteristics of Ustilaginoidae virens and the screening in vitro of the causal pathogen of false smut of rice and fungicides

Green smut bails were collected from diseased rice panicles and surtace sterilized in sodium chloride for 5 minutes. The orange colored internal tissues were placed on PDA medium kept at 25℃ for 5 d to get pure cultures. PDA plates with the pathogen mycelial pieces in diameter of 5mm were incubated under 9 temperature grades ranged from 13 to 35℃.     

Retreat of catabolites of filaments,lodicules,and stigma cells in rice

The lodicules expand rapidly when the rice florets are opening, and the filaments elongate and the stigmas extend and bend. All these growing movements are caused by the cell elongation or expansion after water absorption. The lodicules, filaments, and stigma will wither after flowering, but the cause of the withering remains unknown. In some wild abortive male sterile lines, the closing of florets     

Effects of 4PU-30 on leaf senescence and degration of protein and nucleic acid in rice

4PU—30[N—phenyl—'N—(2—chloro—4—pyridyl) urea] is a new type of plant growth regulator with cytokinin properties. It has been confirmed to delay rice leaf senescence effectively. In order to elucidate the physiological role of 4PU—30 in delaying senescence, the changes of protein, nucleic acid contents, and the related activities of degradative enzymes were studied. Shanyou 63, an indica hybrid rice was used for this experiment. In the in vitro experiment, two full—developed leaves from the top during heading stage were collected and cut into 5.0cm segments, They were floated on the surface of distilled water containing 0.1mg/14PU—30 and incubated in darkness at 30 C. The leaves floated on distilled water were used as control.It was observed that chlorophyll content in controlled leaves declined rapidly started from the second day and dropped by 93.4% on the 6th day while that in leaves treated with 4PU—30 declined by 41.4% only. During senescence, specific activities of hemoglobin—digesting     

Bumper harvest of super rice in south and north China

Ｒｅｃｅｎｔｌｙ，ａｇｒｅａｔｐｒｏｇｒｅｓｓｗａｓｍａｄｅｉｎｂｒｅｅｄｉｎｇａｎｄｃｕｌ ｔｉｖａｔｉｏｎｏｆｓｕｐｅｒｒｉｃｅｉｎＣｈｉｎａ．ＴｈｅＳｏｕｔｈＤｅｍｏｎｓｔｒａｔｉｏｎＡｃｃｅｐｔａｎｃｅＭｅｅｔｉｎｇｏｆＣｈｉｎａＳｕｐｅｒＲｉｃｅｗａｓｈｅｌｄｉｎＯｃｔ１７，２０００ｉｎＸｉｎｃｈａｎｇＣｏｕｎｔｙ，ＺｈｅｊｉａｎｇＰｒｏｖｉｎｃｅ．ＹｉｅｌｄｍｏｎｉｔｏｒｉｎｇｇｒｏｕｐｏｒｇａｎｉｚｅｄｂｙｔｈｅＤｅｐａｒｔｍｅｎｔｏｆＳｃｉｅｎｃｅ，ＴｅｃｈｎｏｌｏｇｙａｎｄＥｄ…