Physiological Processes Contributing to the Difference in Grain Amino Acid Content between Two Hybrid Rice (Oryza sativa L.) Cultivars

Improving grain amino acid content of rice (Oryza sativa L.) is essential for the health of consumers. This study was conducted to identify the physiological processes that contribute to the higher grain amino acid content in hybrid rice cultivar Lingliangyou 268 compared to Luliangyou 996. The results showed that total amino acid content in grains was 9% higher in Lingliangyou 268 than in Luliangyou 996. There was no significant difference in grain nitrogen (N) content between Lingliangyou 268 and Luliangyou 996, while ratio of amino acid to N was 6% higher in Lingliangyou 268 compared to Luliangyou 996. A total of 16 differentially expressed proteins related to amino acid metabolism (e.g., erythronate-4-phosphate dehydrogenase domain containing protein) were identified in grains between Lingliangyou 268 and Luliangyou 996. The identified proteins were involved in 10 molecular functions. Six of the 10 defined functions were related to binding (heterocyclic compound binding, nucleoside phosphate binding, nucleotide binding, organic cyclic compound binding, protein binding, and small molecule binding) and the other 4 defined functions were catalytic activity, enzyme regulator activity, hydrolase activity, and transferase activity. These results indicate that the higher grain amino acid content in Lingliangyou 268 compared to Luliangyou 996 is attributed to increased efficiency of converting N to amino acid that results from altered expression of proteins related to amino acid metabolism.     

温光对稻米蛋白质及氨基酸含量的影响

研究水稻结实期的温、光条件对稻米蛋白质与氨基酸含量的影响,其结果表明：同一品种作为早季栽培时,稻米氨基酸含量比作晚季栽培时低,分期播种时,以结实期日平均气温为２４℃时蛋白质含量为最高;不同海拔高度种植时,以８００ｍ处蛋白质含量为最高;结实期人工高温处理,稻米蛋白质和氨基酸含量降低,低温（２１／２０℃）处理时,粳稻的氨基酸含量增加而籼稻则有所降低,籼稻氨基酸形成的适温在２４￣２６℃之间,弱光下,糙米     

The QTL controlling amino acid content in grains of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis>) are co-localized with the regions involved in the amino acid metabolism pathway

The improvement of grain quality, such as protein content (PC) and amino acid composition, has been a major concern of rice breeders. We constructed a population of 190 recombinant inbred lines (RILs) from a cross between Zhenshan 97 and Nanyangzhan to map the quantitative trait locus or loci (QTL) for amino acid content (AAC) as characterized by each of the AACs, total essential AAC, and all AAC. Using the data collected from milled rice in 2002 and 2004, we identified 18 chromosomal regions for 19 components of AAC. For 13 of all the loci, the Zhenshan 97 allele increased the trait values. Most QTL were co-localized, forming ten QTL clusters in 2002 and six in 2004. The QTL clusters varied in both effects and locations, and the mean values of variation explained by individual QTL in the clusters ranged from 4.3% to 28.82%. A relatively strong QTL cluster, consisting of up to 19 individual QTL, was found at the bottom of chromosome 1. The major QTL clusters identified for two different years were coincident. A wide coincidence was found between the QTL we detected and the loci involved in amino acid metabolism pathways, including N assimilation and transfer, and amino acid or protein biosynthesis. The results will be useful for candidate gene identification and marker-assisted favorable allele transfer in rice breeding programs.     

Rice growth improvement and grains bio-fortification through lime and zinc application in zinc deficit tropical acid sulphate soils

A two years field study was conducted to explain the effect of Zn and lime application on morphological characteristics, rice yield and yield components, and more broadly, grains bio-fortification (Zn and protein content (CP), and amino acid profiles). The lime and Zn interaction increased grains and straw yield more than two times (6.64 ton ha^?1) compared to the control (3.20 ton ha^?1). The maximum increase in the Zn content of grain, white rice and bran was obtained about 30% in whole grain, 42% in bran and 56% in white rice. Furthermore, CP increased by about 8% in bran, 12.3% in whole grain, and 27% in white rice compared to control. Also, the Zn and lime application and their interaction were significantly increased the amino acids, especially essential parts.     

不同施肥水平对不同品种小麦籽粒蛋白质和地上器官游离氨基酸含量的影响

研究了小麦不同品种开花后各地上器官游离氨基酸含量的变化动态及其与籽粒蛋白质含量的关系,以及氮素营养的调节作用。结果表明,小麦叶片和颖壳十穗轴游离氨基酸含量均在开花后持续增加,至花后14d达到最大值,之后开始下降。茎和叶鞘游离氨基酸含量则在开花后上升较缓慢,至花后21d达最大值。籽粒游离氨基酸含量一般在开花后就持续降低。各地上器官游离氨基酸含量与成熟期籽粒蛋白质含量均呈显著或极显著正相关,说明源器宫中游离氨基酸供应充足,有利于籽粒蛋白质积累。增施氮肥能够提高各地上器官中的游离氨基酸含量,进而促进籽粒蛋白质的合成,提高籽粒蛋白质含量。品种之间籽粒蛋白质含量的差异,是由各地上营养器官向籽粒运输氨基酸的综合作用所造成的。     

Profiling the Expression of Genes Controlling Rice Grain Quality

Rice provides a staple source of energy, protein and other nutrients to half of the world population. Over 90 of the rice seeds consists of starch and protein by dry weight. The quantity and property of starch and protein thus play a dominant role in the yield and quality of rice. The amylase content of starch is a determining factor in the eating and cooking quality while the amount and essential amino acids balance of storage proteins affect the nutritional quality of rice. In China, the super-hybrid rice currently under the last phase of development has a 35 yield advantage over the best inbred rice varieties. However, its grain quality needs further improvement. This study reported the expression patterns of 44 genes participating in starch, storage protein, and lysine synthesis in the developing rice grain. Field grown rice cultivar 9311, the paternal line of an elite super-hybrid rice LYP9with its draft genomic sequence released, was used as plant material. Results revealed diverse yet coordinated expression profiles of the genes involved in the three pathways which lead to the final composition and property of starch, protein and lysine that determine the quality of rice, providing useful information for rice quality improvement.     

Changeability of protein fractions and their amino acid composition during maturation of barley grain

The formation of the protein complex during barley grain maturation is characterized by unequal synthesis of different protein fractions. In ten day-old grain the dominating protein is glutelin, followed by albumin and globulin. The content of prolamin is at this stage negligible. Particularly after the eighteenth day of maturation intensive synthesis of prolamins begins, which continues during the entire maturing period in almost the same ratio as total N accumulation in the grain. From the twenty-fourth day the amount of prolamins exceeds that of glutelins, and at full maturity 50% of the proteins are prolamins. The glutelin content increases absolutely, but relatively it decreases from 41 to 26%. The amino acid composition of flour from total grain as well as the amino acid composition of the individual proteins is significantly changed during maturation. Generally the changes are manifested in an increasing content of Glu and Pro and a decreasing content of Asp, Ala and Lys. These changes seem to occur as a result of an increasing representation of prolamin, which is characterized by large content of Glu and Pro and low content of Asp, Ala and Lys compared with other protein fractions.     

长期轮作对黄土高原旱地小麦籽粒蛋白质营养品质的影响

在长期定位试验条件下,研究了黄土高原旱地粮草（小麦-红豆草）、粮豆（小麦-豌豆）和粮饲（小麦-玉米）3种典型轮作制度对小麦籽粒蛋白质营养品质的影响.结果表明： 轮作制度及茬口年限可对黄土高原旱地小麦籽粒蛋白质营养品质产生不同程度的影响.与连作小麦相比,实行小麦-红豆草轮作后,小麦籽粒蛋白质营养品质较稳定,且其籽粒蛋白质必需氨基酸含量、氨基酸评分、氨基酸比值系数、化学评分和氨基酸指数均较高,可作为黄土高原生产优质蛋白小麦的轮作制度;小麦与豌豆进行轮作,豌豆茬后1年小麦籽粒蛋白质营养品质较高,但豌豆茬后2年小麦籽粒蛋白质必需氨基酸含量较低,且多种必需氨基酸评分和化学评分低于连作小麦,必需氨基酸指数比连作小麦低12.2%,营养品质较低;虽然粮饲轮作小麦籽粒蛋白质营养品质较稳定,但其粗蛋白、必需氨基酸含量及氨基酸平衡程度均低于连作小麦.     

Quality and safety evaluation of genetically engineered rice with soybean glycinin: analyses of the grain composition and digestibility of glycinin in transgenic rice

The composition of nutritionally and physiologically important molecules in transgenic rice with the soybean glycinin gene was determined and compared with that of a non-transgenic control. Except for the levels of protein, amino acids and moisture, no marked differences were found between the two kinds of rice. The protein content of the transgenic rice was about 20% higher than the control (control, 6.5 g/100 g; transgenic, 8.0 g/100 g) with a concomitantly lower moisture content. This increased protein content mainly resulted from the increased glycinin expressed in the transgenic rice, and the protein was susceptible to gastric and intestinal digestion juices. In parallel with the increased protein content, some important amino acids lacking in quantity in normal rice were replenished.     

Biochemical factors affecting protein accumulation in the rice grain

Rice grains (Oryza sativa L.) from three varieties and three pairs of lines with different protein content were collected at 4-day intervals from 4 to 32 days after flowering. The samples were analyzed for protein, free amino nitrogen, ribonucleic acid, protease activity, and ribonuclease activity. In addition, the capacity of the intact grain to incorporate amino acids was determined for the three pairs of lines. The maximal level of free amino nitrogen and the capacity of the developing grain to incorporate amino acids were consistently found to be higher in the samples with the high protein content in the mature grain. The ribonucleic acid content of the grain tended to be higher in the high protein samples.     

Effect of Adding the Limiting Amino Acids to an Amino Acid Diet Simulating Rice Protein on the Conversion of Tryptophan to Nicotinamide in Rats

The effect of amino acid composition on the conversion ratio of tryptophan to nicotinamide was investigated. The ratio in the group fed with an amino acid diet simulating rice protein was around 2.5%. This ratio was statistically decreased by the addition of the limiting amino acids, except for tryptophan, and increased by the addition of all the limiting amino acids, including tryptophan. The composition of amino acids proved to greatly affect the conversion ratio.     

植物源调节剂对水稻的影响

植物源调节剂是利用艾蒿为主要原料,首次用提取的混合物研制成的一种植物生长调节剂,使用80mg/L的植物源调节剂混合物水溶液,分别在水稻苗期、拔节期、孕穗期叶面喷洒,清水对照。结果表明:植物源调节剂使水稻增产11.38%,千粒重增加11.45%。株干重增加了17.1%。在灌浆期连续测定表明:相对于CK,穗粒重增加10.9%,叶绿素含量提高14.41%。品质分析结果为:可溶性糖含量提高15.57%、游离氨基酸含量提高18.52%、淀粉含量提高1.59%,可溶性蛋白质降低22.17%、粗纤维降低1.95%、粗脂肪降低1.22%。该植物源调节剂对水稻的生长和产量都有显著的促进效应。     

Properties of glutelin from mature and developing rice grain

Aminograms and SDS-polyacrylamide electrophoresis of milled rice glutelin of 12 Oryza sativa samples showed similar composition and ratio of 1 : 1 : 1 for subunits with MW 38 000:25 000: 16 000, indicating little possibility of finding variants of rice glutelins. Fractionation of S-cyanoethyl glutelin of 3 rices on polyacrylamide-agarose gels gave MW subunits differing in amino acid analysis of which the subunits with MW > 38 000 had the highest lysine content. Of the solubility fractions of endosperm glutelin, the fraction extracted by 0.5 M NaCl-0.6 % β-mercapto-ethanol-0.5% SDS was closest to glutelin in properties. In the developing grain of two varieties, appearance of protein bodies and rapid synthesis of glutelin from 7 days after flowering onward coincided with a drop in lysine content and appearance of MW 38 000 and 25 000 of crude glutelin. The MW 38 000 subunit is thus unique to endo-sperm glutelin.     

Amino acid composition of maize silage produced in the United Kingdom

The amino acid composition of the silage dry matter, silage nitrogen (g/16 gN) and the molar composition of the total measured amino acids (mM/100 mM) of five maize silages was measured and compared with results from the U.S.A.As the dry matter content of the silages increased, the total amino acid content decreased but was generally higher than values reported from America. As the grain content of the silages increased there was a decrease in lysine content which was reflected in an increased concentration of glutamic acid and proline. The lysine content of U.K. silages was higher than those from the U.S.A.     

Mutational bias affects protein evolution in flowering plants

Amino acid sequences from several thousand homologous gene pairs were compared for two plant genomes, Oryza sativa and Arabidopsis thaliana. The Arabidopsis genes all have similar G+C (guanine plus cytosine) contents, whereas their homologs in rice span a wide range of G+C levels. The results show that those rice genes that display increased divergence in their nucleotide composition (specifically, increased G+C content) showed a corresponding, predictable change in the amino acid compositions of the encoded proteins relative to their Arabidopsis homologs. This trend was not seen in a "control" set of rice genes that had nucleotide contents closer to their Arabidopsis homologs. In addition to showing an overall difference in the amino acid composition of the homologous proteins, we were also able to investigate the biased patterns of amino acid substitution since the divergence of these two species. We found that the amino acid exchange matrix was highly asymmetric when comparing the High G+C rice genes with their Arabidopsis homologs. Finally, we investigated the possible causes of this biased pattern of sequence evolution. Our results indicate that the biased pattern of protein evolution is the consequence, rather than the cause, of the corresponding changes in nucleotide content. In fact, there is an even more marked asymmetry in the patterns of substitution at synonymous nucleotide sites. Surprisingly, there is a very strong negative correlation between the level of nucleotide bias and the length of the coding sequences within the rice genome. This difference in gene length may provide important clues about the underlying mechanisms.     

Storage-protein Deposition in the Developing Rice Caryopsis in Relation to the Transport Tissues

The developing caryopsis of rice (Oryza sativa L.) was examinedhistologically at successive stages of grain-filling in orderto identify the factors which determine the distribution ofstorage protein in the endosperm, and which terminate the depositionof endosperm protein. The storage protein was deposited at theperiphery of the endosperm, and this distribution was apparentlycaused by the radial pattern of cell development in the endosperm,and by the proximity of the peripheral endosperm cells to thenucellar epidermis. The nucellar epidermis directly surroundsthe endosperm and functions as the pathway for amino acid transportto the endosperm. During the later stages of caryopsis developmentthe nucellar epidermis became compressed by being ‘sandwiched’between the expanding endosperm and the rigid hull (the tightlylocked palea and lemma) which encloses the caryopsis. It isproposed that this compression of the nucellar epidermis blocksthe supply of amino acids to the endosperm and thereby terminatesthe deposition of storage protein in the rice grain. Oryza sativa, rice, caryopsis (development), endosperm, grain filling, nucellar epidermis, storage protein     

Amino acid composition of two varieties of sorghum grain

The purpose of the present study was to investigate the animo acid composition of 5 different samples of C Hara sorghum grain and to estimate the biological values of their protein fraction by means of some chemical indexes, such as the the chemical score, biological value, essential amino acid index and the protein balance index.The figures obtained were compared with those of 5 different samples of sorghum grain belonging to the variety NK 121 and with those of common maize grain. C Hara appeared to have the highest amount of crude protein with the lowest biological value, but when protein digestibility figures were considered, C Hara had the highest content of biologically utilizable proteins.     

Free and bound amino acids and proteins in developing grains of rice with enhanced lysine/proteins

 Free amino acids were determined in developing seed of a rice mutant with enhanced grain lysine. This phenotype frequently has enhanced protein. Some free amino acids of developing seed are inversely related to the level of total amino acids in proteins of the mature grain. Amino acids that were enhanced in protein, including aspartic acid, threonine, methionine and lysine, were notably lower in the free amino-acid pool. Our conclusion is that mutant-developing grains process aspartate amino acids more rapidly than the controls. Conversely, arginine, valine and glutamic acid/glutamine accumulate as free amino acids with mutant/control ratios of 1.39, 1.29 and 1.12, respectively. Glutamic acid/glutamine in proteins of mature seeds is lower in the mutant than the control. ³H-lysine incorporation showed enhanced isotope incorporation into at least four proteins. One mutant protein was less actively labelled than analogous controls. The ³Hlysine pattern indicates processing modifications in this useful rice mutant. Received: 14 October 1996/Accepted: 8 November 1996