三种愈伤组织中质体的DNA含量变化及其与水稻花粉白苗形成的关系

以质体为单位的愈伤组织ptDNA的荧光强度变化显示出了特有的规律性,结合光培养花粉白苗叶质体结构的电镜观察及叶绿素等色素的测定等,这种规律性似提示花粉白苗的ptDNA由于发生了相继缺失而显示出高度异质性,花粉白苗的形成则在于其占优势ptDNA的严重缺失,花粉白苗ptDNA的这种相继缺失不是随机的,似反映了ptDNA顺序组织上的特点,故ptDNA发生缺失的潜在可能性具有普遍意义,它与父系细胞质体类核的消失存在着并行关系,花粉白苗的占优势ptDNA指导的植株的性状,而次要ptDNA亦在较小程度上显示出影响。     

水稻花粉白苗成因的研究——Ⅰ、化学诱变剂对水稻花粉白苗发生的影响

用化学诱变剂甲基磺酸乙酯(EMS)、乙烯亚胺(EI)和1—甲基—3—硝基—1—亚硝基胍(MNNG)处理培养早期的水稻花药,观察到花粉白苗的形成增加而绿苗的形成减少。因此花粉总苗数中白苗所占的百分数显著增高,例如用 EMS 2.5ml/1在26℃处理品种8126的培养花药,花粉苗中白苗为34.9％,而对照为6.7％。但即使在这种情况下,所培养出的花粉植株中只有很少数发生性状突变。白苗也在少数绿色花粉植株后代中出现,其频率第二代比第三代高100倍以上。试验结果有利于认为水稻白化苗的成因可能是培养花粉中某些基因的缺失。化学诱变剂处理导致较多花粉发育成白苗,这对于试图利用水稻培养花粉进行诱变以便获得某种突变体是一大障碍。     

活性炭对水稻花粉植株的壮苗作用

在水稻花培育种中,花粉植株的成活率与试管苗的素质关系极大。水稻的花药经人工培养形成愈伤组织再分化成绿苗,经过这一复杂的过程,形成各种形态的植株,研究花粉植株发     

禾本科植物花药培养中的白化现象

白化花粉植株〔花粉白苗）的产生是禾本科植物花 药培养的特征之一。除葡萄外‘333,还未见在禾本科以 外的植物甲有花粉白苗的报道。禾本科植物的子房培 养“03、原生质体培养‘,,,、幼穗培养“,,’“,’．,及幼胚培 养[t37等再生植株中也有白苗,但远不如花粉植株中白 苗比例高。在大麦、水稻和小麦的花粉植株中,白苗往 往占1/3以上,有时高达90%。白化现象已成为禾本 科植物花药培养应用于育种实践的重要障碍之一。     

小麦不同发育时期花药的花粉白苗分化初探（简报）

花粉白苗的研究,以水稻为材料的较多,且大多研究培养基成分、培养温度、培养材料等对白苗分化的影响、花粉白苗的亚显微结构及遗传生化分析等。但就花粉白苗的成因问题目前仍不清楚。我们对小麦不同小孢子发育时期的花药分别培养,初步探讨了花粉白苗分化与小孢子发育时期之间的关系。     

水稻花药培养中小孢子形成植株的组织分化和器官建成的初步观察

以 N_6为基本培养基培养水稻花药,用压片法及石蜡制片法,对小孢子形成植株的过程进行组织分化和器官建成的观察。结果表明,从小孢子到花粉植株形成分两个阶段:愈伤组织的形成和不定根、不定芽的分化。小孢子(花粉)第一次有丝分裂形成两个均等细胞,而后这两个细胞再经过多次分裂,形成愈伤组织。由愈伤组织中发生的不定根是内生源的。芽是外生源的,即愈伤组织表面的一部分细胞,经过反分化形成分生组织,而后这种分生组织再进一步分化成芽。不定根和不定芽在开始时是独立发生的,它们之间没有维管组织联系。从外部形态上看,当花粉形成植株时,都是先出芽而后出现根。但从解剖上看,可能也有不定根发生早于不定芽的现象。     

从“湖北光敏感核不育水稻”的未受精子房和花药培养出单倍体植株

采用10种诱导培养基,培养湖北光敏感核不育水稻农垦58品种的未受精子房和花药。共培养未受精子房2790个,获得胚囊愈伤组织17块,最高诱导频率达3.33%,其中2块分化出绿苗。培养花药16740个,获得花药愈伤组织15块,最高诱导频率为0.92%,其中3块分化出苗,2丛白苗,1株绿苗。胚囊植株和花粉植株经根尖染色体检查为单倍体,2n=x=12。实验证明,液体培养、2,4-D0.2-0.5 mg/1、低温预处理对诱导胚囊愈伤组织及花粉愈伤组织的形成具良好效果。     

扁豆花粉发育的超微结构

用透射电镜对扁豆ＤｏｌｉｃｈｏｓｌａｂｌａｂＬ．的小孢子发生和雄配子体形成过程进行了观察。首次观察到扁豆花粉发育过程中,其质体与线粒体去分化、再分化发生于整个花粉发育过程中,并经历了两个去分化和再分化的周期。     

基因型对春麦花粉植株诱导率影响的研究

花药培养中,不同基因型供体对于花粉植株的影响很大.几年来的研究结果表明,用花培品系做亲本配置杂交组合;不同世代的基因型,尤其是F_1代花药供体植株;亲本基因型在提高花粉愈伤组织出愈率、花粉绿苗分化及花粉绿苗率方面均有明显的效果.     

玉竹雄配子的发育——着重阐明质体在生殖细胞和营养细胞中的分布和变化

玉竹(Polygonatum simizui Kitag)小孢子在分裂前,质体极性分布导致分裂后形成的生殖细胞不含质体,而营养细胞包含了小孢子中全部的质体。生殖细胞发育至成熟花粉时期,及在花粉管中分裂形成的两个精细胞中始终不含质体。虽然生殖细胞和精细胞中都存在线粒体,但细胞质中无DNA类核。玉竹雄性质体的遗传为单亲母本型。在雄配子体发育过程中,营养细胞中的质体发生明显的变化。在早期的营养细胞质中,造粉质体增殖和活跃地合成淀粉。后期,脂体增加而造粉质体消失。接近成熟时花粉富含油滴。对百合科的不同属植物质体被排除的机理及花粉中贮藏的淀粉与脂体的转变进行了讨论。     

Chlorophyll Accumulation in Leaves of Rice Pollen Albinos

In contrast to the green plantlets, rice pollen albinos contain a little chlorophyll only, and the relative contents of protochlorophyll (ide) and carotenoids comparing with chlorophyll are much higher however. The contents of chlorophyll and related pigments in leaves of pollen albinos vary regularly with the variation of light regimes. The spectra of regenerated albinos from pollen albinos possess the same characteristics as described above, but their pigment contents are lower. It is likely that the occurrence of these characteristics of pollen albinos may be attributed to their deficiency of plastid membrane system and the latter in turn may be the result plastom mutation. In view of the variation of pigment contents among different planoets of the same variety, it is resonable to deduce that plastids of pollen albinos are heterogeneous structurally and functionally.     

The deficiency of soluble proteins and plastid ribosomal RNA in the albino pollen plantlets of rice

Summary The components of soluble protein and ribosomal RNA in green and albino pollen plantlets of rice were studied by means of polyacrylamide gel electrophoresis. The results were as follows: (1) Soluble protein: the soluble proteins in green pollen plantlets may be fractionated into 15 bands of varying intensities in which the highest content and the most prominent one is band 3 (fraction I protein). Band 3, however, is nearly absent in albino pollen plantlets. (2) Ribosomal RNA (rRNA): rRNA of high molecular weight in green pollen plantlets may be fractionated into 4 bands, i.e. 25S RNA and 18S RNA in cytoplasmic ribosomes, and 23S RNA and 16S RNA in plastid ribosomes. Little or no 23S RNA and 16S RNA, however, is found in albino pollen plantlets. Together with the evidence obtained by other workers, it is suggested that albino forms of pollen plantlets is caused by the impairment of DNA.     

水稻、小麦花药培养白化苗质体亚显微结构和蛋白质的研究

通过对小麦和水稻花药培养白化苗质体的电镜观察,表明白化苗质体早期发育正常,但没有观察到正常的成熟叶绿体。对白化苗质体的类囊体膜蛋白的分析表明,它缺乏细胞核编码的chla/b AP_2,质体DNA编码的chla AP_2和chla AP_3。质体DNA编码的ATPasc的α、β亚基显示了分子量和含量的变化。色素蛋白质的分析表明在白化苗质体中有两种小分子置的色素蛋白存在。文章还对产生上述结果的原因进行了讨论。     

Differential development of plastids during microspore embryogenesis in barley

Summary In order to understand and limit albino plantlet formation during pollen embryogenesis in barley (Hordeum vulgare L. cv. Igri), plastid feature was followed during pollen embryogenesis under two anther culture conditions and compared to plastid development in the zygotic embryo. The first condition was characterized by cold pretreatment and maltose in the induction medium. Both embryos and calli were then obtained. During pollen embryo development, up to 30% of plastids had abnormal features. Disruptions mainly affected the plastid size, the feature of plastid envelopes, thylakoid and granum organization, as well as starch accumulation. In pollen calli, superficial cells had meristematic features. Up to 50% of plastids exhibited the above mentioned abnormalities. Internal cells were highly vacuolated with amyloplast-like plastids; envelopes had normal features but no internal membrane was detected. Pollen embryo-derived plantlets had a green-to-albino ratio (G/A) being equal to 1.0, whereas calli-derived embryos only formed albino plantlets. The second condition was characterized by mannitol pretreatment and the presence of both maltose and mannitol in the induction medium. No callus was formed but most of microspore-derived structures developed haploid embryos and then the green plantlets (200 plantlets per 100 responding anthers, G/A=9.4). In this case, plastid development in zygotic and pollen embryos were similar and almost no albino plantlets were formed.     

A Nuclear Mutation in Nicotiana sylvestris Causing a Thiamine-Reversible Defect in Synthesis of Chloroplast Pigments

We report the recovery of a nuclear recessive mutation in Nicotiana sylvestris (Spegazzini and Comes) producing a conditional disruption in the pathway for synthesis of chlorophyll a and b and carotenoids which is fully reversible by exogenous thiamine (0.3 micromolar). In the absence of supplemental thiamine, chlorophyll levels declined by 50% after 5 days, and fell to undetectable levels by 11 days. Mitochondrial (KCN sensitive) respiration rates remained normal in albino leaves (80% loss of chlorophyll), suggesting that chlorosis results primarily from a deficiency of thiamine in the chloroplasts. After thiamine removal, mutant plants produced at least 10 albino leaves with a substantial capacity for growth (0-15 centimeters; 70-fold increase in area), demonstrating sustained operation of many cellular functions in spite of chloroplast disruption. Activities of the plastid isozymes of phosphoglucomutase and phosphoglucoisomerase in albino leaves indicated that the decline in pigment synthesis does not result from a general loss of metabolic activity in chloroplast. Plastid pyruvate dehydrogenase from mutant and wild-type plants displayed a similar affinity for thiamine pyrophosphate, showing that chlorosis does not result from an alteration in this enzyme. Growth of albino leaves and ultrastructural evidence for thylakoid membranes in the chloroplasts suggest that a certain level of fatty acid synthesis is maintained after the interruption of pigment synthesis. Since thiamine deprivation is expected to block production of acetyl-coenzyme A from pyruvate by pyruvate dehydrogenase, acetyl-coenzyme A supporting fatty acid synthesis in albino leaves may be derived solely from mitochondrial acetate.     

Plastid differentiation during androgenesis in albino and non-albino producing cultivars of barley (Hordeum vulgare L.)

In order to better understand androgenic albinism in barley, we compared plastid differentiation during anther culture in two cultivars, an albino (spring cultivar Cork) and a non-albino (winter cultivar Igri) producing cultivar. The ultrastructure of plastids and the relative amount of DNA containing plastids were followed in both cultivars during the androgenic process and correlated with the proportion of regenerated chlorophyllous plantlets. For androgenesis, anthers were collected at the uninucleate stage, during mid- or late-microspore vacuolation. At this stage DNA was detected in 15.3 ± 2. 7% of microspore plastid sections in the winter cultivar Igri, compared to 1.7 ± 0.5% in the spring cultivar Cork. In the winter cultivar Igri, starch was broken down after anther pretreatment but plastids divided rapidly during anther culture and thylakoids developed in the stroma. Prior to regeneration, plastids contained 2.0 ± 0.2 thylakoids per plastid and starch represented 26.1 ± 3.3% of the plastid volume. In the spring cultivar Cork, plastids followed a different developmental pathway. After anther pretreatment, microspore plastids differentiated exclusively into amyloplasts, accumulating starch and losing their thylakoids as well as their capacity to divide. This developmental pattern became progressively more marked, so that by the end of anther culture plastids contained 0.5 ± 0.4 thylakoids per plastid and starch represented up to 90.3 ± 4.3% of plastid volume. Following androgenesis, the response was similar in both cultivars except that the winter cultivar Igri provided 87.8% of chlorophyllous plantlets compared to 99.7% albino plantlets in the cultivar Cork. The results presented here suggest that the exclusive regeneration of albino plantlets in the spring cultivar Cork may be due to degradation of microspore plastid DNA during early pollen development, preventing the plastids from differentiating into chloroplasts under culture conditions. Received: 13 March 2000 / Revision accepted: 6 June 2000