绿豆子叶衰老期间核酸代谢的变化

萌发绿豆的子叶自然衰老期间,核酸含量降低,RNA降低的幅度比DNA大。电泳分析结果表明,子叶衰老期间细胞核主带DNA明显降低;而迁移慢的卫星带DNA变化不大。在RNA各组分中,18S rRNA从衰老前期就开始降低;25S rRNA和4～5S小分子RNA到衰老后期才缓慢下降。DNase和RNase活性在子叶整个衰老期间都明显升高,是导致核酸含量下降的主要原因。~3H-核苷掺入试验表明,核酸的合成速率在子叶衰老前期有所上升,到衰老后期又降低。poly(A)~ -mRNA含量在子叶开始衰老时明显上升。     

莲胚发育与核酸,蛋白质含量的变化

莲胚发育达到最大鲜重(开花后21d)前,胚轴和子叶的DNA,RNA都持续增长。开花13d后,蛋白、淀粉等贮藏物质显著积累,核酸增长速度加快。成熟胚轴的DNA和RNA含量很高,而子叶中积累大量的淀粉、可溶性糖和蛋白质。发育前期胚乳的生长速度较快,开花后16d左右鲜重和物质积累达到高峰。胚生长后期胚乳逐渐败育,贮藏物质和结构物质都减少,膨大的子叶逐步取代了胚乳的地位。 莲胚生物大分子物质含量的模式属于双子叶植物类型。讨论了莲胚细胞多倍化的问题。     

表油菜素内酯对油菜幼苗生长及其可溶性糖和蛋白质含量的影响(简报)

表油菜素内酯（epiBR）处理油菜幼苗，可明显促进下胚轴伸长生长，增加子叶面积，同时降低蛋白质含量及子叶中可溶性糖含量。SDS－PAGE检测分白结果表明，epiBR处理后，下胚轴和子叶中的蛋白组分均发生明显的改变。     

表油菜素内酯对油菜幼苗生长及其可溶性糖和蛋白质含量的影响…

表油菜素内酯处理油菜幼苗,可明显促进下胚轴伸长生长,增加子叶面积,同时降低蛋白质含量及子叶中可溶性糖含量,ＳＤＳ－ＰＡＧＥ检测蛋白结果表明,ｅｐｉＢＲ处理后,下胚轴和子叶中的蛋白组分均发生明显的改变。     

平贝母体细胞胚胎发生中的核酸与蛋白质合成研究

在获得比较理想的平贝母体细胞胚胎发生体系的基础上,我们应用放射性同位素液体闪烁计数技术测定了平贝母体细胞胚胎发生过程中球形胚、心形胚、鱼雷胚、子叶胚和成熟胚等时期的DNA、RNA和蛋白质合成动态,实验表明,从球形胚到子叶胚,核酸与蛋白质的合成速度递增。在子叶胚前期RNA合成达到高峰,在子叶胚期蛋白质合成达到高峰,在子叶胚后期DNA合成达到高峰,核酸与蛋白质合成速度的变化与胚体细胞增殖及器官分化相关联。     

发育和早萌中花生胚胚轴与子叶内BAPAase活性的差异

花生胚发育过程中,子叶和胚轴中都出现BAPAase活性。花生种子萌发时,子叶和胚轴中的BAPAase活性迅速上升,子叶中无新的BAPAase合成,胚轴中能重新合成BAPAase。ABA抑制了子叶和胚轴中BAPAase的活性,抑制胚轴中BAPAase活性所需的外源ABA浓度更高,Act-D和CHM不能逆转ABA对BAPAase活性的抑制作用。     

去胚轴对花生子叶肽链内切酶和贮藏蛋白质降解的影响

从离体子叶与连体子叶在水中培养一段时间后的比较,看到它们之间在肽链内切酶活性和盐溶蛋白及花生球蛋白降解上的差异并不大,这表明去除胚轴对子叶肽链内切酶活性和贮藏蛋白降解的影响很轻微。亚胺环己酮(蛋白质合成抑制剂)不能完全抑制离体子叶肽链内切酶活性的提高,子叶的大部分大分子贮藏蛋白同样被降解。这表明,在花生种子萌发过程中降解大部分贮藏蛋白的子叶肽链内切酶并非全部是在种子萌发时新合成的,子叶贮藏蛋白降解和肽链内切酶活性基本不受胚轴调控,子叶与胚轴之间在调控关系上可能是一种新的调节类型。     

绿豆幼苗上胚轴伸长生长与细胞渗透势的相关性

在水分供应正常的情况下,切除1/4～1/2的绿豆子叶对上胚轴生长没有明显的抑制作用,但是经0.2M甘露醇处理的幼苗却随着切除的子叶量的增加,上胚轴的生长呈直线剧减,全部切除子叶的幼苗生长几乎完全停止。子叶在水分胁迫状况下对生长的这种作用与它在上胚轴生长区渗透调节中的作用密切相关。幼苗上胚轴的生长与细胞的有效渗透势之间的相关系数为-0.76,有较高的相关性,但是生长与细胞的总渗透势无相关性(相关系数为-0.29)。细胞的渗透势与细胞液中的糖、游离氨基酸和钾离子浓度之间有很高的相关性。表明水分胁迫下生长所需的低渗透势的维持依赖于来自子叶的渗透物质。     

柞蚕卵巢中核酸和蛋白质的分布与含量的变化

本文报道柞蚕卵巢亚细胞组分中核酸和蛋白质的分布与含量变化。首先以差速离心盼方法从卵巢匀浆中分离出细胞核、重线粒体、轻线粒体、重微粒体、轻微粒体和105,000g上清六个组分,然后分别测定了各种组分中的DNA、RNA和蛋白质的含量。 结果表明,卵巢DNA主要分布在细胞核组分中(约占75%以上);RNA在佩粒体中含量较离(约占20—51%);蛋白质则主要分布于105,000g上清组分中(约占56—83%)。卵巢中核酸和蛋白质含量(毫克/头)在滞育蛹期很低,随着卵巢的发育迅速增长。DNA在发育蛹4期最高,比滞育蛹期增长61倍;RNA在发育蛹5期最高,比滞育蛹期增长144倍;蛋自质在成虫期达到高峰,约比滞育蛹期增长490倍。并讨论了核酸和蛋白质的含量变化与卵巢细胞分裂分化之间的关系。 为了获得进一步的生化资料,对不同时期的柞蚕卵巢105,000g上清组分中的蛋白质进行了聚丙烯酰胺凝获也泳和SDS-电泳的分析。初步推测柞蚕卵巢中卵黄蛋白亚基之一的分子量大约为200,000道尔顿。     

脱水敏感的黄皮种子在发育中的可溶性蛋白变化

黄皮种子的子叶与胚轴,在发育前期蛋白质合成速率均高于后期。在发育过程中子叶的可溶性蛋白含量无明显变化,但在后期能新合成少数低分子量的热不稳定蛋白,可能是引起种子萌发的水解酶类。胚轴中可溶性蛋白单位干重含量高于子叶,而其成分不随发育而变化。ABA可促进发育后期黄皮种子胚轴中20kD蛋白的合成,但不能改变种子的脱水敏感性。     

Nucleic Acid and protein metabolism of senescing and regenerating soybean cotyledons

An alternative to the leaf disk system for studies of the metabolism of senescence is described. The progress of senescence of soybean (Glycine max L.) cotyledons is arrested when the epicotyl is removed. Epicotyl removal at 16 or 17 days reversed the decline in nucleic acid, protein, and chlorophyll content in the cotyledon. Epicotyl removal at 18 days did not reverse the decline in the above components, and therefore the progress of cotyledon has passed the point of no return. Cotyledons lost 90% of their nucleic acid and 80% of their protein before senescence became irreversible. The rate of recovery in various macromolecular components after epicotyl removal did not occur in an equal manner. Nucleic acid was regenerated at a faster rate than chlorophyll, which was regenerated at a faster rate than soluble protein. The heavy nucleic acid components (ribosomal and heavy ribosomal messenger fractions) regenerated at greater rates than did the soluble RNA or DNA. No label from ¹⁴CO₂ was incorporated into DNA of the cotyledons when the epicotyl was present but label was incorporated into DNA after epicotyl removal.     

萌发绿豆子叶衰老期间蛋白质代谢的变化

萌发绿豆子叶自然衰老过程中可溶性蛋白质含量一直下降;从衰老开始到衰老前期,总游离氨基酸含量明显上升;但游离氨基酸各组分在子叶衰老期间的变化趋势并不相同。~3H-亮氨酸掺入蛋白质试验和多聚核糖体的相对量及其与总核糖体的比值(P/T)测定都证明在子叶衰老前期有蛋白质的新合成。子叶衰老期间。氨肽酶活性明显降低;而以酪蛋白为底物的蛋白水解酶活性却急剧上升,承担着催化蛋白质降解的主要功能。     

萌发绿豆子叶衰老期间的呼吸作用与线粒体功能的改变

暗中培养的绿豆幼苗子叶在萌发后3—4天时,外观出现衰老征状,6天后子叶凋落。随子叶日龄的增加,子叶的呼吸强度一直下降,呼吸商始终小于1。当外加L—苹果酸、a—酮戊二酸、琥珀酸和NADH为底物测定离体线粒体氧化活性时,衰老子叶的线粒体对上述四种底物的氧化活性有不同程度的增加;抗氰呼吸也有所升高。子叶衰老时,线粒体的ADP／O和呼吸控制(RC值均降低);线粒体ATPase水解ATP的活性升高。衰老绿豆子叶线粒体氧化磷酸化偶联效率的降低和ATPase水解活性的增强是与线粒体结构改变相联系的一种功能变化,它导致能量亏缺,并进一步加速了衰老的恶化进程。     

Studies on energy status and mitochondrial respiration during growth and senescence of mung bean cotyledons

Several characteristics of mitochondrial respiration and energy status have been studied during growth and senescence of mung bean ( Phaseolus radiatus L.) cotyledons. The results showed that mitochondrial oxygen consumption, respiratory control, ADP:O ratios, and energy charge changed in the cotyledons during germination and growth of the seedlings. The respiration rate of intact cotyledons approximately reflected the trend of the oxidative activities of the isolated mitochondria. An increase was observed in both whole cotyledon respiration and mitochondrial oxygen uptake at the onset of senescence of mung bean cotyledons (day 3 after germination), which thereafter declined gradually. The capacity and activity of the alternative pathway increased markedly in mitochondria isolated from senescent cotyledons. After the onset of senescence, the mung bean cotyledon mitochondria exhibited a decrease both in the respiratory control ratios and ADP:O ratios, and the cotyledons exhibited a gradual decline in energy charge. All these results showed an irreversible deterioration of energy conservation in mung bean cotyledons. The role(s) of the alternative pathway in senescent mung bean cotyledons is discussed.     

Osmoregulation in hypocotyls of etiolated mung bean seedlings with or without cotyledons in response to water-deficient stress

Effects of water-deficient stress and cotyledon excision on osmoregulation in hypocotyls of dark-grown mung bean seedlings were studied, and following results were obtained. Water-deficient stress inhibited hypocotyl elongation either in intact or decotylized seedlings. The inhibition was more conspicuous in decotylized seedlings than in intact ones. Water-deficient stress decreased osmotic potential in hypocotyls, while cotyledon excision increased it. The concentrations of soluble sugars, free amino acids and potassium ions in hypocotyls of intact or decotylized seedlings increased in response to water-deficient stress. Cotyledon excision reduced the concentration of soluble sugars and free amino acids, but it did not change the concentration of potassium ions, suggesting that a part of soluble sugars and free amino acids is transported from cotyledons. Unlike cotyledon excision, excision of the apex or roots had no influence on osmoregulation in response to water-deficient stress. Segments excised from hypocotyls had the ability to osmoregulate in response to water-deficient stress. Based on these results, the role of cotyledons in osmoregulation in response to water-deficient stress and quantitative relationships between osmotic potential and hypocotyl elongation in etiolated mung bean seedlings are discussed.     

Influence of the axis on the enzymes of protein and amide metabolism in the cotyledons of mung bean seedlings

The growth of the mung bean (Vigna radiata) seedling is accompanied by the biosynthesis and accumulation of the endopeptidase vicilin peptidohydrolase and the catabolism of the reserve proteins in the cotyledons. If the axis is removed from the dry seeds and the cotyledons incubated on moist sand the accumulation of vicilin peptidohydrolase is reduced by 77% and the catabolism of reserve proteins slowed to 25% of the rate in intact seedlings. The cotyledons and the cotyledon exudate are rich in asparagine and this amino acid accounts for more than half of the reduced nitrogen exported from the cotyledons. Glutamine synthetase and asparagine synthetase, two key enzymes in the pathway of asparagine synthesis, are under temporal control in the cotyledons. Their activities increase 3.5- and 10-fold, respectively, then decline again. These increases in enzyme activity occur to the same extent in excised cotyledons and are prevented when the cotyledons are incubated in 5 micromolar cycloheximide. The results indicate that the axis may control certain key metabolic events in the cotyledons, such as the synthesis of vicilin peptidohydrolase, while many other anabolic activities may not depend on a growing axis.     

表油菜素内酯对绿豆上胚轴内源IAA及其氧化酶的影响

用0.5ppm表油菜素内酯处理绿豆幼苗,显著促进上胚轴伸长生长,若切除真叶则可抑制表油菜素内酯诱导的效应。三碘苯甲酸(TIBA)也可抑制表油菜素内酯促进的伸长生长。外源IAA能部分恢复TIBA的抑制效应。经处理的上胚轴内源IAA含量明显高于对照。暗示表油菜素内酯可能通过对内源IAA的调节来促进绿豆上胚轴的伸长生长。 表油菜素内酯处理的绿豆上胚轴组织中,与生长素降解密切相关的IAA氧化酶以及过氧化物酶活性均明显低于对照。     

Identification of nucleases related to nutrient mobilization in senescing cotyledons from French bean

The knowledge about the physiological function of plant nucleases is scarce besides that they have been involved in nucleic acid degradation related with programmed cell death processes. Cotyledons provide a suitable system to investigate this process and the changes associated to nutrient mobilization. Nuclease activities have been determined in French bean seedlings. The total nuclease activity in French bean cotyledons is lower than in embryonic axes; however, several nucleases were detected by in-gel nuclease activity assays with extracts from cotyledons of French bean and ssDNA as substrate. The nuclease activities induced during cotyledon senescence showed higher activity at neutral than at acidic pH. Five different nuclease genes belonging to S1/P1 family have been identified in French bean genome database named PVN1 to PVN5. Their relative expression in cotyledons has been determined from the start of imbibition to senescence, and three genes from this family showed expression in cotyledons. PVN1 was expressed during early stages of seedlings development, whereas PVN4 and PVN5 were expressed during cotyledons senescence. The removal of epicotyl in French bean seedlings resulted in a decrease in the activity and in the expression of the genes associated with the cotyledons senescence process, i.e. PVN4 and PVN5. At the same time, the mobilization of reserves in those cotyledons was slowed down. In the same way, the deficit in phosphate and nitrate during seedlings development led to an acceleration of induction of these genes at the same time that reserves were utilized early on the time. Therefore, the induction of PVN4 and PVN5, the two S1 nuclease genes involved in the process of cotyledon senescence, is related to nutrient mobilization, supporting a possible role for nucleic acids in nutrient recycling during cotyledon senescence.