DON抑制小麦种胚细胞周期启动的研究

小麦种子在０．５－４．０ｍｇ／Ｌ的脱氧雪腐镰刀菌烯醇（ＤＯＮ）中溶液中萌发,用流式细胞仪检测胚细胞的周期时相并观察黄化苗的生长。结果表明,对照组胚细胞在萌发１２ｈ开始启动细胞周期,此后Ｓ期细胞比率迅速增加并在２０ｈ达到最大值,较萌发１０ｈ的６．５％增加１．７８倍,约１４％的胚细胞在萌发的２２－２６ｈ间完成第一次分裂;ＤＯＮ抑制Ｇ１期胚细胞的启动,小麦胚中Ｓ期细胞比率随ＤＯＮ浓度增加呈指数下降,３．     

电子束辐射对大妻种胚核酸合成活性的损伤效应

电子束辐射损伤大麦种胚核酸合成能力的效应主要表现在使ＤＮＡ复制合成启动推迟,使ＤＮＡ复制、ＲＮＡ合成活性下降,吸涨过程中大麦种胚的ＤＮＡ复动过程。２００与４００Ｇｙ电子束辐射分别使ＤＮＡ复制合成活性的抑制作用强于对ＲＮＡ合成活性的抑制。在５０－５００Ｇｙ范围内,大麦种胚ＤＮＡ复制、ＲＮＡ合成活性均随辐射剂量呈指数下降,其半对数斜率分别为－０．００３９与－０．００１４。根据实验计算,电子束辐射对ＤＮ     

超低能重离子注入作物育种的原初物理机制

从原子核物理学观点出发,采用理论分析与实验测量并举的方法对超级能（〈２００ｋｅｖ）重离子（Ｚ≥６）注入作物（小麦）种子进行诱变育种的原初物理机制进行了研究,结果表明,无论是注入离子本身的射程,还是次级电子,自由基扩散,高温热穗,级联原子和冲击波等次级作用范围都无法触及表皮下面的胚细胞,但注入离子在麦胚内主要元素（Ｃ,Ｎ,Ｏ,Ｓ,Ｐ,Ｋ,Ｃａ）上激发出的特征Ｘ－射线,在其强度减弱为原来的１０＾－３时     

簇毛麦低拷贝cDNA序列的克隆和鉴定

从簇毛麦叶片中提取总ＲＮＡ,进一步分离ｍＲＮＡ。以ｍＲＮＡ为模板反转录合成ｃＤＮＡ,两端经Ｔ４ＤＮＡ多聚酶修平后加ＥｃｏＲ１接头分子,连接于质粒ｐＧＥＭ－７Ｚｆ（＋）的ＥｃｏＲ１克隆位点,转化大肠杆菌ＪＭ１０３菌株建立了ｃＤＮＡ文库。用ＰＣＲ扩增重组质粒的ｃＤＮＡ插入序列,用＾３２Ｐ标记后分别与ＨｉｎｄⅢ或ＸｂａⅠ酶切的小麦－黑麦附加系ＤＮＡ进行Ｓｏｕｔｈｅｒｎ杂交。根据其杂交结果,目前已鉴定出４     

细胞外Ca^＋＋对脉冲式和持续性鲑GnRH类似物刺激鲤GtH分泌的影响

２ｍｉｎ脉冲式１０ｎｍｏｌ鲑ＧｎＲＨ高效类似物ｓＧｎＲＨ－Ａ（Ａｒｇ＾６Ｔｒｐ＾７Ｌｅｕ＾８Ｐｒｏ＾９ＮＥｔ－ＬＨＲＨ）刺激导致离体灌流培育的鲤脑垂体迅速产生显著的ＧｔＨ分泌峰,ＧｔＨ分泌在刺激后３０ｍｉｎ内恢复到基础水平。４ｈ１０ｎｍｏｌ／Ｌ ｓＧｎＲＨ－Ａ持续性刺激导致灌流培育的鲤脑垂体ＧｔＨ分泌出现脱敏反应,整个过程包括刺激后迅速的ＧｔＨ分泌峰相和随后持续低水平的ＧｔＨ分泌相。无Ｃａ＾＋＋的     

Cd2+、Al3+对蚕豆(Vicia faba)DNA合成及修复的影响

利用＾３Ｈ－ＴｄＲ掺入方法,研究了不同浓度单金属离子Ｃｄ＾２＋、Ａｌ＾３＋对蚕豆ＤＮＡ合成、ＤＮＡ修复（以ＵＤＳ为指标）的影响。结果表明：在低浓度Ｃｄ＾２＾＋、Ａｌ＾３＋（Ｃｄ＾２＋浓度〈２００ｍｇ／ｌ,Ａｌ＾３＋浓度１００ｍｇ／ｌ）处理后,蚕豆ＤＮＡ合成加快,并且不同程度地诱导了ＵＤＳ的发生;但在高于此浓度的Ｃｄ＾２＋、Ａｌ＾３＋作用下,蚕豆ＤＮＡ合成受抑制,浓度越高,抑制作用超强;并且几乎不表     

5—羟色胺对肺动脉平滑肌细胞在缺氧条件下增殖的作用

本研究应用细胞培养、＾３Ｈ－ＴｄＲ掺入,核酸分子杂交、免疫组织化学染色技术,探讨无氧（０％Ｏ２＋９５％Ｎ２＋５％ＣＯ２）和／或低氧（２．５￣３％Ｏ２＋９２％Ｎ２＋５％ＣＯ２）对新生小牛肺动脉平滑肌细胞增殖和５－羟色胺转载体基因表达的影响。结果表明：无氧２４ｈ可刺激ＰＡＳＭ的ＤＮＡ合成,＾３Ｈ－ＴｄＲ的掺入增加（Ｐ〈０．０５）,加入５－羟色胺能非常显著地促进无氧ＰＡＳＭ增殖（Ｐ〈０．００１）,而对常     

2,4—D和乙烯利对辣椒花柄离区DNA和蛋白合成的影响

乙烯利处理后０￣４ｈ,辣椒花柄离区ＤＮＡ和蛋白质合成显著增加;２５０ｍｇ·Ｌ＾－１乙烯利处理后３２ｈ辣椒落花率达１００％,２,４－Ｄ处理的离区ＤＮＡ合成量降低,处理后０￣４ｈ促进离区蛋白质合成,４￣２４ｈ蛋白质合成量逐渐降低,１０ｍｇ·Ｌ＾－１ ２,４－Ｄ处理可抑制落花。     

钙通道阻滞剂对肾上腺素能受体激动剂促血管平滑肌细胞增殖的抑制

本工作观察到１０＾－６－１０＾－５ｍｏｌ／Ｌ去甲明上腺素（ＮＥ）用１０＾－７－１０＾－５ｍｏｌ／Ｌ异丙基肾上腺素（ＩＳＯ）可明显促进离体培养的血管平滑肌细胞（ＶＳＭＣ）的增殖和ＤＮＡ的合成,并呈剂量依赖效应,该效应可为相应的受体阻断剂ｐｈｅｎｔｏｌａｍｉｎｅ（１０＾－６ｍｏｌ／ｌ）和ｐｒｏｐｒａｎｏｌｏｌ（１０＾－５ｍｏｌ／Ｌ）所抑制;ｎｉｆｅｄｉｐｉｎｅ（１０＾－６ｍｏｌ／Ｌ）和ｖｅｒａｐａｍｉ     

脂多糖对离体培养大鼠血管平滑肌细胞增殖的影响

本研究观察到１０－７～１０－５ｋｇ／Ｌ脂多糖（ｌｉｐｏｐｏｌｙｓａｃｈａｒｉｄｅ,ＬＰＳ）可显著促进血管平滑肌细胞（ＶＳＭＣ）的增殖及ＤＮＡ的合成（Ｐ＜００５）。５×１０－４～１０－３ｋｇ／ＬＬＰＳ却抑制ＶＳＭＣ的增殖及ＤＮＡ的合成,降低其活力（Ｐ＜００１）,并呈时间依赖效应。一氧化氮合酶抑制剂ＮＮｉｔｒｏＬＡｒｇｉｎｉｎｅ（ＬＮＮＡ）可拮抗ＬＰＳ的抑制作用。大剂量ＬＰＳ作用组ＶＳＭＣ上清液中一氧化氮（ＮＯ）代谢产物ＮＯ－３和ＮＯ－２的含量与对照组相比显著增加（Ｐ＜００１）,４８ｈ组比２４ｈ组增加９１％,７２ｈ组比４８ｈ组增加４５％;同时,诱导性一氧化氮合酶（ｉｎｄｕｃｔｉｖｅｎｉｔｒｉｃｏｘｉｄｅｓｙｎｔｈａｓｅ,ｉＮＯＳ）免疫组化染色呈阳性。结果表明,低浓度ＬＰＳ促进ＶＳＭＣ增殖和ＤＮＡ合成,而高浓度ＬＰＳ却明显抑制ＶＳＭＣ增殖和ＤＮＡ合成,降低其活力。这种抑制作用可能与ＬＰＳ诱导ＶＳＭＣ产生的ＮＯ有关。     

花生种子萌发早期胚轴细胞DNA合成的特点

花生种子吸胀6h后胚轴DNA中有~3H-胸苷掺入。咖啡因和羟基脲均对6～12h的~3H—胸苷掺入具强烈的抑制作用;当12～24h时,咖啡因的抑制作用较大;但30h以后,羟基脲的抑制作用超过咖啡因。双链DNA放射性从种子吸胀9h后迅速上升,单链DNA放射性在吸胀12h后出现一个明显的峰。但在吸胀12h后,单链DNA形成和存在的时间是短暂的。     

赤霉素与脱落酸对番茄种子萌发中细胞周期的调控

利用细胞流检仪检测番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．） ＧＡ－缺陷型、ＡＢＡ－缺陷型和相应的正常品种（野生型）成熟种子胚根尖细胞倍性水平时发现：ＧＡ－缺陷型和野生型种子绝大多数细胞ＤＮＡ 水平为２Ｃ,而ＡＢＡ－缺陷型种子则含有较多的４Ｃ细胞。在标准发芽条件下,ＡＢＡ－缺陷型和野生型种子浸种１ ｄ 后胚根尖细胞ＤＮＡ 开始复制,随后胚根突破种皮而发芽。然而ＧＡ－缺陷型种子除非加入外源ＧＡ,否则既不发生细胞ＤＮＡ 复制,也不发芽。这说明内源ＧＡ 是启动番茄种子胚根尖细胞ＤＮＡ 复制的关键因素,同时也说明番茄根尖细胞ＤＮＡ 复制是种子发芽的必要条件。实验证明：ＡＢＡ 不抑制细胞ＤＮＡ 合成,但阻止Ｇ２ 细胞进入到Ｍ 期。外源ＡＢＡ处理野生型种子与渗控处理结果相似,可以大幅度提高胚根尖４Ｃ／２Ｃ细胞的比例,但抑制种子的最终发芽     

Endoreduplication in cucumber (Cucumis sativus) seeds during development, after processing and storage, and during germination

Flow cytometry was used to study endoreduplication in developing, stored and germinating seeds of cucumber ( Cucumis sativus ). Fruits growing in a commercial seed production field were collected every 7 days, starting 14 days after pollination (DAP) up to 63 DAP (commercial harvest time). Seeds were isolated and the proportion of nuclei with different DNA contents in the whole seeds and in the embryos was analysed. Germination capacity of fresh and dried seeds at 25°C was established. In addition, the same analyses were performed on the seeds after processing (fermentation, drying and cleaning), following 1 and 2 years of storage, and after imbibition for 3, 6 and 12 h. In the young developing seeds, endoreduplication up to 128C occurred but this decreased to 8C by maturity. The proportion of endosperm nuclei was the highest at 21 DAP (30%) and then decreased to below 14% at harvest and 8% after processing. In the mature processed seeds, the majority of embryo nuclei (about 80%) contained 2C DNA; however, about 2% of endoreduplicated (8C) nuclei were still present. Seeds did not show any germination capacity up to 21 DAP; then it gradually increased to reach 100% as early as 49 DAP, 2 weeks before commercial harvest time. The relationship between seed maturity, germination and cell cycle status is discussed. The mean C-value of the seed cells as well as the (4C + 8C + 16C)/2C ratio are recommended as markers of cucumber seed maturity and the advancement of germination/priming (the stage of germination sensu stricto ).     

Lack of correlation between overall protein synthesis and the onset of cell elongation in germinating embryos of Haplopappus gracilis

10⁻⁵M abscisic acid (ABA) completely inhibits germination or (if seeds deprived of integuments are used) embryo elongation in Haplopappus gracilis (Nutt.) Gray. Nevertheless, considerable rates of protein and RNA synthesis were found in embryos grown in abscisic acid, at least during the early hours after sowing. On the contrary, seeds grown in cycloheximide + fusicoccin (a powerful promoter of cell expansion), where protein synthesis is almost completely inhibited, show full protrusion of radicle, thus simulating a "germination" process. These results suggest that some of the most important events involved in seed germination, i.e. protein and RNA synthesis, and cell elongation which leads to radicle protrusion, may not necessarily be linked together and are possibly regulated by different control mechanisms. Moreover, when seeds or embryos are grown in abscisic acid + fusicoccin, protein synthesis is considerable, cell elongation is greater than in water controls at least for 12 h, and germination in its early stages appears to be normal; but DNA synthesis and cell division are not resumed, possibly since some other factor is required. All these findings propose a reevaluation of criteria for defining successful germination.     

Nucleic acid and protein synthesis and loss of vigour in germinating wheat embryos

A study has been made of the RNA and protein synthesising systems of wheat embryos isolated from seed lots having high viability but differing in vigour. The rate of RNA and protein synthesis in wheat embryos during the early hours of germination is related to the vigour of the seed lot. The imposition of a stress factor, in the nature of a sub-optimal germination temperature, during germination of isolated wheat embryos magnifies the differences in rates of protein and RNA synthesis between high and low vigour seed. Using cell-free protein synthesising systems it has been demonstrated that an important difference between high and low vigour embryos lies in the relative levels of messenger RNA in the embryo. High vigour embryos contain relatively higher levels of poly A⁺-RNA (i.e. potential mRNA species) than lower vigour embryos and furthermore the level of poly A⁺-RNA in high vigour embryos increases during early germination whilst in lower vigour embryos the level decreases. The difference in poly A⁺-RNA levels accounts, at least partially, for the differences in rates of protein synthesis observed between embryos from high and low vigour wheat seed during early germination at both optimal and sub-optimal germination temperatures.Abbreviations HEPES N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid - poly A⁺-RNA polyadenylated RNA - GM germination medium - PMS post-mitochondrial supernatant fraction     

Wheat aging: the contribution of embryonic and non-embryonic lesions to loss of seed viability

A study has been made to identify the contribution of senescent changes occurring in embryonic and non-embryonic (endosperm and aleurone layer) tissues on germination of wheat ( Triticum durum L. cv. Appulo) seed lots of 97, 93 and 70% viability. Measurements of germination and rates of macromolecular synthesis of embryos excised from dry seeds showed that as seed viability declined from 97 to ca 93%, there was a decrease in the capacity of embryos to grow and synthesise protein, RNA and DNA. However, no significant differences were observed between embryos from 93 and 70% viability seed stocks. Changes in nutrients, fresh and dry weights of embryonic and non-embryonic tissues and electrophoretic patterns of endosperm proteins by sodium dodecyl-sulfate polyacrylamide gel electrophoresis showed a reduced mobilisation of reserve material in 70%-viable seeds. α-Amylase (EC 3.2.1.1) production was also decreased. It is suggested that alterations occurring in non-embryonic structures play a significant role in seed viability loss. This role might be mediated by failing nutrient supply, but the involvement of some inhibitor or toxic substance is also possible.     

GA and ABA Regulation on the Cell Cycle in Germination of Tomato Seeds

Flow cytometric determination of ploidy levels in embryos of GA-deficient, ABA-deficient mutant and isogenic wild type tomato (Lycopersicon esculentum Mill. cv. Moneymaker) seeds revealed that, large amount of 2C DNA signals existed both in wild type and GA-deficient mutant seeds, showing that most cells had arrested in the cell cycle at presynthesis Gl, whereas a relative amount of 4C proportion which is a sign of seed germination was found in ABA-deficient mutant seeds, indicating that endogenous ABA play a role in regulating the switch from development to germination in seeds. DNA replication was stimulated 1 d after the seed was imbibed in water and a visible germination occurred subsequently either in wild type GA-deficient mutant seeds. But it was not the case for ABA-deficient mutant seeds unless an exogenous GA was supplemented. This demonstrated that DNA replication in embryo root tips cells was subjected to be a compulsory factor for seed germination, whereas endogenous GA triggered DNA synthesis. It was evident that exogenous ABA could inhibit seed germination not by suppressing DNA synthesis but by bloking the route leading to mitosis since a great amount of 4C proportion was found in the germinating wild type and GA-deficient mutant seeds in the ABA solution when visible ger mination did not occur. Finally a simple mode of hormonal regulation on cell cycle in high plants was hypothesized.     

DNA and histone synthesis are uncoupled during germination of maize embryos

The rate of synthesis of DNA and histones was studied in germinating maize embryos as a function of the length of the germination period. To that end excised embryos from seeds germinated for different periods of time were pulse labelled either with [¹⁴C]protein hydrolysate or with [³H]TdR. Specific activities were determined for the total cellular proteins and the total histone fraction obtained by acid-extraction of the cellular homogenate and BioRex70 ion exchange chromatography. The results show that the early germination period is characterized by a lack of coupling between the histone synthesis and that of the nuclear DNA. The early histone synthesis peak might be necessitated by the reprogramming of the embryo genome that takes place during germination.     

A wheat homolog of MOTHER OF FT AND TFL1 acts in the regulation of germination

Seed dormancy is an adaptive mechanism and an important agronomic trait. Temperature during seed development strongly affects seed dormancy in wheat (Triticum aestivum) with lower temperatures producing higher levels of seed dormancy. To identify genes important for seed dormancy, we used a wheat microarray to analyze gene expression in embryos from mature seeds grown at lower and higher temperatures. We found that a wheat homolog of MOTHER OF FT AND TFL1 (MFT) was upregulated after physiological maturity in dormant seeds grown at the lower temperature. In situ hybridization analysis indicated that MFT was exclusively expressed in the scutellum and coleorhiza. Mapping analysis showed that MFT on chromosome 3A (MFT-3A) colocalized with the seed dormancy quantitative trait locus (QTL) QPhs.ocs-3A.1. MFT-3A expression levels in a dormant cultivar used for the detection of the QTL were higher after physiological maturity; this increased expression correlated with a single nucleotide polymorphism in the promoter region. In a complementation analysis, high levels of MFT expression were correlated with a low germination index in T1 seeds. Furthermore, precocious germination of isolated immature embryos was suppressed by transient introduction of MFT driven by the maize (Zea mays) ubiquitin promoter. Taken together, these results suggest that MFT plays an important role in the regulation of germination in wheat.     

Respiratory Transition during Seed Germination

Experiments with germinating seeds of Wayne soybean (Glycine max Merr.) show that between the 4th and the 8th hour of germination, respiration experiences a transition from predominantly “alternate” respiration, which is sensitive to salicylhydroxamic acid, to a cyanide-sensitive respiration. The dependence of early germination stages on alternate respiration is reflected in several types of seed functions, including subsequent root growth rate, chlorophyll synthesis, and germination itself. The early period of germination is shown to require a normal O₂ tension, which is no longer a requirement at later stages. The changing sensitivity to cyanide and to salicylhydroxamic acid is found to be common to seven different types of germinating seeds. It is proposed that the alternate pathway of respiration provides something essential for the completion of the earliest stages of seed germination.