卫星搭载向日葵种子SP_2代花部变异株的研究

利用卫星搭载向日葵种子后获得的花部变异株,SP2正常株与对照株比较,结果表明:突变株筒状花的花瓣变大、增长,花药变小,而子房和花柱的变化不大。在同一个花盘中,外周花的花瓣长大,而中心部花的花瓣短小。变异株的小孢子增大。精核分化早,呈线状,是观察小孢子精核形态的好材料。     

美味猕猴桃原生质体再生植株细胞遗传学研究 Ⅱ.性别性状变异和小孢子发生及其发育命运

对美味猕猴桃同一雌株叶原生质体再生植株进行了形态学、细胞学以及育性特性的比较研究,确认该体细胞无性系性别性状发生变异。其中60％雄性再生植株退化的雌蕊仍保留不同程度的雌性化特征,但雌性全不育;小孢子则能发育成有功能的雄配子体,但有一定的功能缺陷。再生雌株中P1组群性状特征与母株相似;P2组群花发育畸形,导致雌性不育或育性极差。细胞学研究表明,小孢子母细胞减数分裂时染色体异常行为对小孢子发生的影响不能决定其性别类型;雌株类型小孢子败育过程有受基因调控的细胞学特征。认为雌株和雄株小孢子的发育受控于不同的基因体系,具性别的特异性。再生植株性别性状发生变异可能是性别控制基因或染色体发生结构性变异所致。母株染色体上累积的结构性变异与该遗传基础具易变性密切有关。     

航天诱变凤仙花SP2代形态变异的研究

对经“神舟4号”卫星搭载后的SP2代凤仙花的形态变异进行了研究。结果表明:子叶数目除有了两片的外,尚有三片和四片的。子叶形态上出现连生子叶、杯状子叶和大小不等子叶。真叶的形态上出现线状披针形,其小孢子母细胞减数分裂不正常,小孢子不育。花的结构上出现花瓣增多和花的叶化现象。茎的分枝上,有的不分枝,仅具主茎,有的分枝多达40枝以上。这些变化对研究和认识航天诱变育种有一定的理论和实际的意义。     

美味猕猴桃原生质体再生植株细胞遗传学研究 Ⅱ.性别性状变异和小孢子发生及其发育命运

对美味猕猴桃同一雌株叶原生质体再生植株进行了形态学、细胞学以及育性特性的比较研究,确认该体细胞无性系性别性状发生变异。其中６０％雄性再生植株退化的雌蕊仍保留不同程度的雌性化特征,但雌性全不育;小孢则能发育成有功能的雄配子体,但有一定的功能缺陷,再生雌株中Ｐ１组群性状特征与母株相似;Ｐ２线群花发育畸形,导致雌性不育或育性极差。细胞学研究表明,小孢子母细胞减数分裂时染色体异常行为对小孢子发生的影响不能     

同一居群韭莲不同植株减数分裂行为差异的遗传分析

对韭莲(2n=48)小孢子母细胞减数分裂及小孢子发育进行研究。结果显示同一居群植株的减数分裂行为存在明显差异。多数韭莲植株小孢子母细胞减数分裂存在少量落后染色体、微核等现象,平均每株中具有异常分离行为的母细胞占14.02%,小孢子发育正常,但花粉无活力。并首次从减数分裂后期Ⅰ的特殊的细胞学形态证明韭莲是臂内倒位杂合体。而少数植株韭莲的小孢子母细胞减数分裂极其紊乱,后期Ⅰ出现多极分离、大量落后染色体,小孢子母细胞减数分裂总异常分离高达94.3%。四分孢子期多分孢子体高达73.4%。分析认为:前者减数分裂行为异常的原因主要由染色体结构变异所致,而后者的原因除染色体结构变异外,还可能与控制纺锤体形成的基因突变有关。     

灯盏花雄性不育种质鉴定与花药发育的细胞学研究

对云南泸西栽培灯盏花群体进行调查,发现了灯盏花雄性不育种质个体,其出现频率约为1.06×10-4.对所发现的灯盏花不育株形态特征及其花药发育过程进行了观察,并对花粉活力进行鉴定.结果显示:(1)灯盏花不育株根、茎、叶形态与正常可育植株基本相似,管状花小,花丝短,花药瘦小,无花粉粒散出或花粉无活力.(2)灯盏花在其花药发育的小孢子母细胞时期、四分体时期、小孢子时期和单核早期,由于绒毡层细胞液泡化、提前解体,不能为小孢子或花粉发育提供所需物质,导致小孢子母细胞和四分体解体,产生无花粉的花药;或小孢子和单核花粉胞内降解,形成不同形状和外壁纹饰的败育花粉.研究认为,灯盏花花药绒毡层异常是其花粉败育的主要原因.     

侧柏小孢子的发生和雄配子体的形成

侧柏[Platycladusorientalis（L．）Franco]初生造孢细胞在8月下旬（1992年）形成,11月上旬形成小孢子母细胞,1993年2月中旬形成四分体,2月下旬小孢子从四分体内释放出来,3月中旬形成成熟花粉粒并开始传粉,4月上旬花粉粒在珠心上萌发,5月上旬生殖细胞分裂,6月上旬精原细胞分裂。小孢子母细胞在休眠以前开始减数分裂,解除休眠以后形成成熟的花粒粒。减数分裂从11月上旬开始至次年2月17日结束。小孢子母细胞减数分裂存在扩散双线期。小孢子母细胞以双线期渡过休眠。精原细胞接近颈卵器时开始分裂,形成两个大小相同的精细胞。精细胞独立存在的时间很短。精细胞的细胞质分为三个区域。小孢子母细胞在发育过程中,发现有部分小孢子母细胞退化,在小孢子囊内形成一大的空腔的现象。     

甘薯细胞质传递的研究：精细胞的质体和线粒体及其DNA存在的状况

甘薯（ＩｐｏｍｏｅａｂａｔａｔａｓＬａｍ．）成熟花粉为二细胞型,在授粉后萌发之前生殖细胞分裂形成精细胞。仍在花粉粒中的两个精细胞大小和形状基本相似,细胞质中含丰富的质体和线粒体。细胞质ＤＮＡ特异荧光显示精细胞及产生它们的前细胞———生殖细胞中均含有丰富的类核。一对精细胞中类核的数量无明显的差异。精细胞中存在两种形态类核,大而荧光强的类核可能为质体类核,而小的荧光弱的类核为线粒体类核。双亲或父系质体遗传在被子植物中是少数,本研究结果为旋花科的除牵牛属和打碗花属外又提供了新的一属具这种遗传方式的细胞学证据。     

源于小孢子培养的大麦耐盐变异体获取

以大麦品种‘花30’作为供试材料,比较了甲基磺酸乙酯（EMS）和平阳霉素处理小孢子60Co γ-射线辐照处理离体穗和干种子,对300mg·L-1NaCl胁迫培养下游离小孢子的愈伤组织产量和愈伤组织在0.3％NaCl胁迫筛选下的绿苗产量的影响。结果表明,EMS处理离体小孢子和60Co γ-射线辐照千种子的愈伤组织产量和绿苗产量明显优于平阳霉素处理小孢子和60Co γ-射线辐照离体穗。以16份源于种子辐照处理的再生植株自交一代种子为供试材料,比较了在0．3％NaCl胁迫下种子的发芽率和幼苗的成活率以及植株的分蘖数、株高和单株产量。结果表明,‘花30’发芽率为0,供试的16份耐盐变异体中,有14份材料在NaCl胁迫下的发芽率优于‘花30’,鉴定出4份耐盐性明显优于‘花30’的变异体材料。选择耐盐变异体作为供试材料,测定了变异体中Na＋／H＋逆向转运蛋白基因NHXl、NHX2和NHX3和编码甜菜碱醛脱氢酶（BADH）的两个同工酶基因曰肋,和BBD2的表达模式和表达量,结果表明变异体耐盐性的提高与这些基因的表达量存在联系。     

无花瓣油菜雄蕊心皮化突变体细胞学观察及基因表达分析

油菜是我国重要的油料作物,油菜花器官具有典型的十字花科特点,无花瓣油菜在花期不存在花冠层,这种特点有助于提高油菜产量,预防茵核病的传播。雄蕊心皮化是指花器官的雄蕊结构被具有类似于雌蕊结构的器官代替,这不仅造成了花器官结构的变化也导致了雄性不育。本文通过对无花瓣油菜雄蕊心皮化突变不育分离群体中的雄性可育株和不育株的比较研究,发现心皮化现象是由遗传因素引起的。细胞学观察发现,雄蕊心皮化在花器官发育的早期就已经产生,心皮化的雄蕊中着生类似于胚珠的结构,其顶端细胞的形态和排列方式也与雌蕊柱头相似。花发育相关基因的表达分析表明,B组基因彳丹在不育株3轮花器中的表达都比可育株低,特别是在第二轮花器官中这种差异最为突出。而A组基因AP1在不育株第二轮花器官中的表达量较可育株高。c组基因AGL8、SHPI、SHP2、NAP在不育株心皮化的第二轮花器官中表达都较可育株中高。     

ROXY1, a member of the plant glutaredoxin family, is required for petal development in Arabidopsis thaliana

We isolated three alleles of an Arabidopsis thaliana gene named ROXY1, which initiates a reduced number of petal primordia and exhibits abnormalities during further petal development. The defects are restricted to the second whorl of the flower and independent of organ identity. ROXY1 belongs to a subgroup of glutaredoxins that are specific for higher plants and we present data on the first characterization of a mutant from this large Arabidopsis gene family for which information is scarce. ROXY1 is predominantly expressed in tissues that give rise to new flower primordia, including petal precursor cells and petal primordia. Occasionally, filamentous organs with stigmatic structures are formed in the second whorl of the roxy1 mutant, indicative for an ectopic function of the class C gene AGAMOUS (AG). The function of ROXY1 in the negative regulation of AG is corroborated by premature and ectopic AG expression in roxy1-3 ap1-10 double mutants, as well as by enhanced first whorl carpeloidy in double mutants of roxy1 with repressors of AG, such as ap2 or lug. Glutaredoxins are oxidoreductases that oxidize or reduce conserved cysteine-containing motifs. Mutagenesis of conserved cysteines within the ROXY1 protein demonstrates the importance of cysteine 49 for its function. Our data demonstrate that, unexpectedly, a plant glutaredoxin is involved in flower development, probably by mediating post-translational modifications of target proteins required for normal petal organ initiation and morphogenesis.     

Ectopic endoreduplication caused by sterol alteration results in serrated petals in Arabidopsis

The Arabidopsis frill1 (frl1) mutant, that has serrated petals and sepals but no other large changes in plant morphology, was studied. The frl1 had a mutation in STEROL METHYLTRANSFERASE 2 and an altered sterol composition. It was found that the frl1 mutation causes ectopic endoreduplication in petal tips that do not normally endoreduplicate. The rosette leaves of frl1 also showed an enhanced level of endoreduplication, but their morphology was hardly affected. These facts suggest that the suppression of endoreduplication is important for petal morphogenesis and the normal sterol composition is required for this suppression.     

Patterns of cell division and expansion in developing petals of Petunia hybrida

The definition of the patterns of cell division and expansion in plant development is of fundamental importance in understanding the mechanics of morphogenesis. By studying cell division and expansion patterns, we have assembled a developmental map of Petunia hybrida petals. Cycling cells were labelled with in situ markers of the cell cycle, whereas cell expansion was followed by assessing cell size in representative regions of developing petals. The outlined cell division and expansion patterns were related to organ asymmetry. Initially, cell divisions are uniformly distributed throughout the petal and decline gradually, starting from the basal part, to form a striking gradient of acropetal polarity. Cell areas, in contrast, increased first in the basal portion and then gradually towards the petal tip. This growth strategy highlighted a cell size control model based on cell-cycle departure time. The dorso-ventral asymmetry can be explained in terms of differential regulation of cell expansion. Cells of the abaxial epidermis enlarged earlier to a higher final extent than those of the adaxial epidermis. Epidermal appendage differentiation contributed to the remaining asymmetry. On the whole our study provides a sound basis for mutant analyses and to investigate the impact of specific (environmental) factors on petal growth.     

A petal‐specific InMYB1 promoter from Japanese morning glory: a useful tool for molecular breeding of floricultural crops

Production of novel transgenic floricultural crops with altered petal properties requires transgenes that confer a useful trait and petal‐specific promoters. Several promoters have been shown to control transgenes in petals. However, all suffer from inherent drawbacks such as low petal specificity and restricted activity during the flowering stage. In addition, the promoters were not examined for their ability to confer petal‐specific expression in a wide range of plant species. Here, we report the promoter of InMYB1 from Japanese morning glory as a novel petal‐specific promoter for molecular breeding of floricultural crops. First, we produced stable InMYB1_1kb::GUS transgenic Arabidopsis and Eustoma plants and characterized spatial and temporal expression patterns under the control of the InMYB1 promoter by histochemical β‐glucuronidase (GUS) staining. GUS staining patterns were observed only in petals. This result showed that the InMYB1 promoter functions as a petal‐specific promoter. Second, we transiently introduced the InMYB1_1 kb::GUS construct into Eustoma, chrysanthemum, carnation, Japanese gentian, stock, rose, dendrobium and lily petals by particle bombardment. GUS staining spots were observed in Eustoma, chrysanthemum, carnation, Japanese gentian and stock. These results showed that the InMYB1 promoter functions in most dicots. Third, to show the InMYB1 promoter utility in molecular breeding, a MIXTA‐like gene function was suppressed or enhanced under the control of InMYB1 promoter in Arabidopsis. The transgenic plant showed a conspicuous morphological change only in the form of wrinkled petals. Based on these results, the InMYB1 promoter can be used as a petal‐specific promoter in molecular breeding of floricultural crops.     

The mutants compacta ?hnlich, Nitida and Grandiflora define developmental compartments and a compensation mechanism in floral development in Antirrhinum majus

In order to improve our understanding of floral size control we characterised three mutants of Antirrhinum majus with different macroscopic floral phenotypes. The recessive mutant compacta ?hnlich has smaller flowers affected mainly in petal lobe expansion, the dominant mutant Grandiflora has overall larger organs, whilst the semidominant mutation Nitida exhibits smaller flowers in a dose-dependent manner. We developed a cell map in order to establish the cellular phenotypes of the mutants. Changes in organ size were both organ- and region-specific. Nitida and compacta ?hnlich affected cell expansion in proximal and distal petal regions, respectively, suggesting differential regulation between petal lobe regions. Although petal size was smaller in compacta ?hnlich than in wild type, conical cells were significantly bigger, suggesting a compensation mechanism involved in petal development. Grandiflora had larger cells in petals and increased cell division in stamens and styles, suggesting a relationship between genes controlling organ size and organ identity. The level of ploidy in petals of Grandiflora and coan was found to be equivalent to wild type petals and leaves, ruling out an excess of growth via endoreduplication. We discuss our results in terms of current models about control of lateral organ size.     

Growth and cellular patterns in the petal epidermis of Antirrhinum majus: empirical studies

Background and Aims

Analysis of cellular patterns in plant organs provides information about the orientation of cell divisions and predominant growth directions. Such an approach was employed in the present study in order to characterize growth of the asymmetrical wild-type dorsal petal and the symmetrical dorsalized petal of the backpetals mutant in Antirrhinum majus. The aims were to determine how growth in an initially symmetrical petal primordium leads to the development of mature petals differing in their symmetry, and to determine how specific cellular patterns in the petal epidermis are formed.

Methods

Cellular patterns in the epidermis in both petal types over consecutive developmental stages were visualized and characterized quantitatively in terms of cell wall orientation and predominant types of four-cell packets. The data obtained were interpreted in terms of principal directions of growth (PDGs).

Key Results

Both petal types grew predominantly along the proximo-distal axis. Anticlinal cell walls in the epidermis exhibited a characteristic fountain-like pattern that was only slightly modified in time. New cell walls were mostly perpendicular to PDG trajectories, but this alignment could change with wall age.

Conclusions

The results indicate that the predominant orientation of cell division planes and the fountain-like cellular pattern observed in both petal types may be related to PDGs. The difference in symmetry between the two petal types arises because PDG trajectories in the field of growth rates (growth field) controlling petal growth undergo gradual redefinition. This redefinition probably takes place in both petal types but only in the wild-type does it eventually lead to asymmetry in the growth field. Two scenarios of how redefinition of PDGs may contribute to this asymmetry are considered.