Premeiosis and meiosis in Lilium “Enchantment”

Various aspects of premeiosis and meiosis in Lilium Enchantment are described. There was evidence of a premeiotic slow-down but no cells in premeiotic despiralization were observed. A relationship was found between sequence of bud development, or reproductive age of the individual, and degree of preleptotene chromosome contraction. The sequence of development of microsporocytes in the anther differed from the apex-to-base order previously reported in Lilium and, in contrast to observations in L. longiflorum cultivars, the maximum degree of preleptotene contraction was found in basal, last developing microsporocytes. Delayed despiralization of telophase nuclei was observed. There were extremely rare cells in meiotic division in anthers in which all other archesporial cells had not yet reached premeiotic interphase. Extreme variation was observed among anthers in proportions of microsporocytes in mid-stages of meiosis as well as in preleptotene contraction. These observations are discussed in relation to meiosis readiness, meiotic behavior in early and late developing regions of reproductive organs and in aging individuals, synchrony of meiotic development and rates of meiotic division.     

The Microsporogenesis and Megasporogenesis of Soybean

This article deals with the morphological aspects of the process of megasporogenesis and microsporogenesis in soybean. The tempos of microsporogenesis in different anthers of the same flowers were compared, and it has been found that at the leptone- ma, zygonema, pachynema and diplonema of the first meiotic division there appeared a certain degree of synchrony, while at the uninuclear stage of the microspore a perfect synchrony was observed. The development of different pollen mother cells within the same anther was in most cases highly synchronized. The anther in which the PMCs were found to be in the'near stages of the meiotic divisions accounts for 7% only. The megasporocyte develops later than the mierosporoeyte. It enters into the leptotene stage or diplotene stage of the first meiotic division while the mierosporocyte has already finished the process of the meiotic division. Explantation of plates 1. A section of a partieal mierosporangium, mierospore mother cells and the cells of the anther wall. × 600 2. Mierospore mother cells in zygotene stage (bouquet stage). × 600 3. Pa- chytene stage of first meiotic division. ×530 4. Diakinesis of meiosis Ⅰ, the tapetal cells begin- ning to degenerate. ×900 5. Metaphase Ⅰ. ×630 6. Anaphase Ⅰ. ×630 7. Anaphase Ⅰ. ×370 8 Interphase, two-nucleated dyad condition with no intervening cell walls formed. ×630 9. Me- taphase Ⅱ. ×630 10. Beginning of telophase Ⅱ×370 11, Telophase Ⅱ, four microspore nuclei contained within the original microspore mother cell wall. ×630 12. Uninuclear microspore, ×630     

PATTERNS OF PROTEIN ACCUMULATION IN DEVELOPING ANTHERS OF LILIUM LONGIFLORUM CORRELATE WITH HISTOLOGICAL EVENTS

Differentiation in the anther of Lilium longiflorum occurs in discrete stages that correlate well with flower bud length. Using both sodium dodecyl sulfate and two-dimensional polyacrylamide gel electrophoresis, detectable proteins that accumulated during the development of lily anthers were documented. In terms of histology and protein patterns, anther ontogeny was divided into three major phases. Phase I encompassed early proliferative stages as well as the differentiation of the locules. Phase II extended from the onset of meiosis through to mature microspores. Phase III began after microspore mitosis occurred to form pollen. Ten floral organ-enriched and 17 floral organ-specific polypeptides were detected during development. The appearance and disappearance of these polypeptides correlated well with the transitions between phases. Two groups of floral organ-specific proteins in Phase II were chosen for further analysis. Both groups of polypeptides were stamen-specific. The 15.0 kD proteins were anther-specific and were the most abundant floral proteins detected; the 75.0 kD proteins were detected in both the anther and filament.     

MICROSPOROGENESIS IN PEANUT (ARACHIS HYPOGAEA)

The stage of pollen development at the time of anther culture is an important factor in the production of haploids. The objectives of the current study were to develop a staining procedure for peanut (Arachis hypogaea L., ssp. hypogaea) microspores, to describe and document the stages of microsporogenesis in peanut, and to confirm a previous report concerning correlations of peanut floral bud shape with stage of microspore development. A staining procedure using propionic carmine provided adequate staining of pollen mother cells, microspores, and pollen. Pollen mother cells and microspores could easily be differentiated by their size and cell wall structure. Plants grown in a controlled environment were found to have highly synchronized microspore development, both within an anther and among anthers contained in the same bud. In addition, floral bud shape was confirmed as a reliable indicator of anther stage in peanuts.     

Growth of anthers in Lilium longiflorum

The post-initiation growth of 64 anthers (1.1–17.4 mm long) in Lilium longiflorum Thumb. was examined by time-lapse marking experiments in combination with serial sections and the scanning electron microscope. Each anther was characterized by spatial and temporal variation in growth rate. Larger anthers had two, and occasionally three, series of peaks and troughs in local growth rate. Regions of negative growth rate were frequently encountered. When observed over several days, the growth maxima and minima were found to move basipetally as a waveform down the length of the anther. The wavelength was longer in taller anthers; amplitude and frequency were variable, and anthers of the same size were not always synchronous. Distribution patterns of cell division (and elongation, once division has ceased) recapitulate the growth data. Anther growth is a non-steady system, therefore, with growth centers constantly shifting. Implications for future studies in organ growth patterns are discussed.Abbreviation SEM scanning electron microscope     

LOW RESISTANCE CONNECTIONS BETWEEN CELLS IN THE DEVELOPING ANTHER OF THE LILY

Low resistance junctions were demonstrated between cells in anthers from young buds of Lilium longiflorum Croft by standard electrophysiological techniques. Electrodes containing a dye were used to stain impaled cells for later histological identification. Electrical coupling is widespread; germinal cells are coupled to one another; coupling is also observed between somatic elements, and germinal and somatic cells are similarly interconnected. Cytoplasmic bridges are implicated in the first case; plasmodesmata are probably responsible for the interactions in the other two. Although the physiological role of the low resistance junctions shown here and present in embryonic animal tissues is unknown, the possible function of this form of intercellular communication in the development of the anther is discussed.     

Meiotic metaphase I to telophase II as the most responsive stage during microspore development for callus induction in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis>) anther cultures

The generation of homozygous doubled haploid lines through induction of androgenesis is a promising alternative to the classical inbreeding and selection programs. However, this technology is poorly developed in tomato, where doubled haploid tomato plants have only been obtained through anther culture. Despite the fact that anther culture is routinely used in a number of economically interesting crops, there are still many drawbacks that prevent tomato breeders from adopting this technique, and improvements in methodology are required. One key issue is the correct identification of the optimal stage for anther excision and culture. In this paper we characterise in vivo microsporogenesis in tomato, defining the different microspore stages and relating them to the length of the donor flower bud. In parallel, we cultured anthers of these stages to obtain embryogenic callus, and followed the microscopic development of the callus contained within the anther. Our data suggest that the stage with the highest response, in terms of callus generation, is meiosis. In particular, we propose the window from metaphase I to telophase II, including tetrad cellularisation, as the timeframe where induction can be accomplished in tomato anther cultures.     

Microarray Analysis of Gene Expression Involved in Anther Development in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

In flowering plants, anthers bear male gametophytes whose development is regulated by the elaborate coordination of many genes. In addition, both gibberellic acid (GA₃) and jasmonic acid (JA) play important roles in anther development and pollen fertility. To facilitate the analysis of anther development genes and how GA₃ and JA regulate anther development, we performed microarray experiments using a 10-K cDNA microarray with probes derived from seedlings, meiotic anthers, mature anthers and GA₃- or JA-treated suspension cells of rice. The expression level change of 2155 genes was significantly (by 2-fold or greater) detected in anthers compared with seedlings. Forty-seven genes, representing genes with potential function in cell cycle and cell structure regulation, hormone response, photosynthesis, stress resistance and metabolism, were differentially expressed in meiotic and mature anthers. Moreover, 314 genes responded to either GA₃ or JA treatment, and 24 GA₃- and 82 JA-responsive genes showed significant changes in expression between meiosis and the mature anther stages. RT-PCR demonstrated that gene y656d05 was not only highly expressed in meiotic anthers but also induced by GA₃. Strong RNA signals of y656d05 were detected in pollen mother cells and tapetum in in situ hybridization. Further characterization of these candidate genes can contribute to the understanding of the molecular mechanism of anther development and the involvement of JA and GA₃ signals in the control of anther development in rice.     

Factors affecting variability in anther culture and in conversion of androgenic embryos ofSolanum phureja

The variation for embryo production in anther ofSolanum phureja was examined as a function of maximum greenhouse temperature prior to bud harvest and innate responsiveness among anthers within a bud. Four clones ofS. phuyreja were grown in a greenhouse under a 16-h photoperiod. The temperature was monitored continuously. Buds (60 per day on 10 days) were collected and the anthers cultured in two groups of five flasks (30 anthers per flask). In the first group, each flask contained the 30 anthers from six buds; in the second group, each flask contained one anther from each of 30 buds. Significantly smaller coefficients of variation were observed for the second group, suggesting that variation for embryogenic capcity among buds was greater than that among anthers within a bud. Variation in embryo yield as a function of greenhouse temperature was examined by stepwise regression analysis. Embryogenic capacity of one clone was adversely affected by high temperatures (31–37°C) that occurred two and seven days before bud harvest. However, similarly high temperatures appeared to enhance the androgenic response of another clone. Conversion of anther-derived embryos over three subcultures to fresh regeneration medium was examined as a function of anther donor or clone, cold pretreatment of embryos, and morphological classification of embryos. Only clonal origin significantly affected conversion rate which ranged from 12.5% to 46.0%. Conversion rate declined on each serial subculture.Abbreviations BA N⁶-benzyladenine - GA₃ gibberellic acid, IAA-indole-3-acetic acid     

Asynchronous meiosis in an interspecific hybrid of <Emphasis Type="Italic">Brachiaria ruziziensis</Emphasis> and <Emphasis Type="Italic">B. brizantha</Emphasis>

Male meiosis is generally synchronous in higher plants. The regulation of the cell cycle is still not well understood, and a powerful tool for gaining an understanding of this regulation is the development of mutations that affect cell-cycle synchrony. We report here asynchronous microsporogenesis in an interspecific hybrid between two important tropical grasses. In young spikelets of the interspecific hybrid 49.10% of anther meiocytes entered meiosis, exhibiting typical phases of the first and second divisions, while the other 50.90% showed distinctive features of early prophase. In older spikelets, anthers containing mature pollen grains also displayed meiocytes still undergoing meiosis. At this time, the latter cells were enclosed by the exine wall. Despite asynchrony, all cells completed meiosis. Old anthers contained only pollen grains that appeared to be in the same stage of development. Pollen fertility was estimated to be 52.76% in dehiscent anthers. An independent genetic control for meiosis synchrony and meiotic stages is suggested.     

关苍术两性花与雌花花药的解剖学研究

苍术属(Atractylodes DC.)是菊科菜蓟族(Cynareae)刺苞亚族(Carlininae O. Hoffm.)的一个东亚特有属,世界上仅有7种,其中我国有5种。该研究以关苍术为材料,采用石蜡切片法比较研究了两性花和雌花的花药及雄配子体发育进程,并进一步探讨了其雌花产生花药退化的时期及原因。结果表明：(1)关苍术小孢子发育与花蕾长度间存在相关性,当花蕾长度在5 mm时进入花粉母细胞时期,花药壁已分化,在7~9 mm时处于四分体时期,大于11 mm时开始进入花粉粒时期。(2)关苍术花药5个,花粉囊4个,减数分裂属同时型,四分体以正四面体为主,属3-细胞型,萌发沟3个。(3)关苍术花粉囊壁发育属双子叶型,从外层的表皮、药室内壁,到内层的中层和绒毡层均由一层细胞构成,关苍术绒毡层为腺质绒毡层。(4)关苍术雌花花药退化发生在花药发育早期至四分体时期,表现为花药发育早期畸形、药壁分化异常、小孢子母细胞发育停滞在前期、绒毡层增生4个原因。该研究结果为苍术属植物的系统发育、物种形成和进化提供胚胎学依据。     

LEVER ACTION ANTHERS AND THE FORCIBLE SHEDDING OF POLLEN IN TORENIA (SCROPHULARIACEAE)

The anthers of Torenia fournieri were found to shed pollen forcibly by lever action. Anther structure was modified for this function by a flangelike outgrowth of the lateral pollen sac wall forming a lever. When pressed, this lever causes an infolding of the thinner, subadjacent, pollen sac wall forcing pollen from the stomium. A force of 1–1.5 g pressing against the four levers of an anther pair resulted in the forcible shedding of 2,000–3,000 pollen grains in two parallel rows. During the 2-day anthesis the flowers shift from functioning as males to hermaphroditic outcrossers, and yet only have a pollen:ovule ratio of 98.6, a ratio more indicative of facultative autogamy. The outermost pair of anthers functions on the first day of anthesis, while the second, inner pair functions on both days. In each flower, the 2-day anther pair produces approximately twice as many pollen grains as the 1 -day anther pair, a pollen production highly correlated with the length of their functional lives. This difference in pollen production is apparent in the larger size of the 2-day anthers, a size difference that first appears with the initiation of the anther primordia.     

Microsporogenesis and tapetal development in fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.)

Summary The development of sporogenous and tapetal cells in the anthers of male-fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.) plants was studied using light and transmission electron microscopy. In general, male-sterile anthers showed a much greater variability in developmental pattern than male-fertile anthers. The earliest deviation from normal anther development was observed to occur in sterile anthers at meiotic early prophase: there was a degeneration or irregular proliferation of the tapetal cells. Other early aberrant events were the occurrence of numerous small vesicles in the microspore mother cells (MMC) and a disorganized chromatin condensation. Deviations that occurred in sterile anthers at later developmental stages included: (1) less distinct inner structures in the mitochondria of both MMC and tapetal cells from middle prophase onwards. (2) dilated ER and nuclear membranes at MMC prophase, in some cases associated with the formation of protein bodies. (3) breakdown of cell walls in MMCs and tapetal cells at late meiotic prophase. (4) no massive increase in tapetal ER at the tetrad stage. (5) a general dissolution of membranes, first in the MMC, then in the tapetum. (6) abortion of microspores and the occurrence of a plasmodial tapetum in anthers reaching the microspore stage. (7) no distinct degeneration of tapetal cells after microspore formation. Thus, it seems that the factors that lead to abortive microsporogenesis are structurally expressed at widely different times during anther development. Aberrant patterns are not restricted to the tetrad stage but occur at early prophase.     

POLLINATION AND THE FUNCTION OF FLORAL PARTS IN CHAMAECRISTA FASCICULATA (FABACEAE)

Chamaecrista fasciculata has a rigid upper petal that curves over nine of the ten anthers. The single anther is deflexed, as is the style. An experimental pollination study was designed to test the hypotheses that: 1) the rigid petal acts as flight guide to ensure pollination; and 2) the nine grouped anthers serve as fodder anthers, whereas the single deflexed anther functions in pollination. The rigid petal was removed from 97 flowers. Only 5% of the manipulated flowers set fruit in comparison to a fruit set of 47% for the control group. The results of the study support the flight guide hypothesis. Pollen from both sets of anthers is viable and germinates on receptive stigmas. A pollen flow experiment using powdered metals, backscatter scanning electron microscopy, and X-ray microanalysis revealed that there is no difference in the frequency of pollen distribution from either set of anthers. Therefore, this study refutes the fodder/pollinating anther hypothesis.     

Characterization of an anther-specific glycoprotein in Lilium longiflorum

Antiserum was raised in rabbits against a lily (Lilium longiflorum) anther-specific glycoprotein (LLA-75). LLA-75 protein bound to concanavalin A, suggesting that it was a glycoprotein. Monospecific anti-LLA-75 antibodies were prepared to investigate its distribution during anther development. Immunoblot analyses of total protein from floral and vegetative organs show that LLA-75 glycoproteins accumulated to detectable levels primarily in one discrete stage of anther development, during the microspore and early pollen phase when the tapetum is actively secreting. A cross-reactive protein with molecular mass of 43.0 kD was also observed. Immunoblots of two-dimensional polyacrylamide gels of lily anther proteins indicated that the four isoforms of LLA-75 glycoprotein ranged from isoelectric point 5.6 to 6.1. These affinity purified antibodies to LLA-75 cross-reacted with anther proteins in two dicot species of the Bignoniaceae. In situ localization data using antirabbit immunoglobulin G (IgG) conjugated with gold particles was not definitive but demonstrated that LLA-75 glycoprotein in lily anthers occurred prominently in tapetal tissue and all other tissues to a lesser degree.     

BA对大麦花药培养中药壁的衰退和植株再生频率的影响

用含20ppm 6-BA的0.1％吐温-80溶液喷施花粉为单核前期的大麦上部叶片和穗部,明显影响大麦花药培养效率。实验结果表明:1)BA处理可明显延缓培养花药的药壁衰退进程。2)BA处理后的花药,在培养期间,其死亡的花粉数比对照大大减少,相反其双核或多核的花粉数比对照明显增加。3)BA处理虽然没有促进大麦花粉愈伤组织的诱导率,但显著地促进愈伤组织的生长。提高愈伤组织成长率,增加可转入分化培养的愈伤组织块数。4)BA处理促进愈伤组织的再分化,尤其是绿苗的分化。     

太谷核不育小麦可育花药内游离脯氨酸的来源、利用及与不育花药败育的关系

太谷核不育小麦营养体内的游离脯氨酸能迅速地运入并积累于花药中,花药有将谷氨酸转化成脯氨酸的能力。脯氨酸向花药内以主动运输为主,能被DNP所抑制,与旗叶的功能密切相关。在发育阶段Ⅰ(小孢子释放前后),脯氨酸已不能由营养体运入不育花药,运输的障碍在花丝或花药中,不育花药缺乏游离脯氨酸可能是主要原因。发育阶段Ⅰ的可育花药内,脯氨酸是合成蛋白质或其他大分子物质的原料。因而,脯氨酸的缺乏可能是加速不育花药小孢子败育和小孢子释放后急剧解体的重要原因。