Stages Of Microsporogenesis Research Articles

Cell- and Tissue-Specific Expression of Rice Histone Gene Transcripts During Anther and Pollen Development in Henbane (Hyoscyamus niger)

We have monitored by in situ hybridization the cell- and tissue-specific expression of a rice histone H3 gene during anther and pollen development in henbane (Hyoscyamus niger). Autoradiographic silver grains generated by hybridization of 35S-labeled antisense probe were present in more or less the same density in all the cells of the anther primordium. During later development of the anther, there was a sequential accumulation of histone mRNA beginning in the epidermis on the outside and ending in the tapetum inside. These changes in transcript abundance in the sporophytic cells of the anther were also related to the stage of microsporogenesis. Transcript level increased during sporogenesis and reached a maximum in mature pollen grains collected from open flowers.

CELL‐ AND TISSUE‐SPECIFIC EXPRESSION OF RICE HISTONE GENE TRANSCRIPTS DURING ANTHER AND POLLEN DEVELOPMENT IN HENBANE (HYOSCYAMUS NIGER)

We have monitored by in situ hybridization the cell‐ and tissue‐specific expression of a rice histone H3 gene during anther and pollen development in henbane (Hyoscyamus niger). Autoradiographic silver grains generated by hybridization of 35S‐labeled antisense probe were present in more or less the same density in all the cells of the anther primordium. During later development of the anther, there was a sequential accumulation of histone mRNA beginning in the epidermis on the outside and ending in the tapetum inside. These changes in transcript abundance in the sporophytic cells of the anther were also related to the stage of microsporogenesis. Transcript level increased during sporogenesis and reached a maximum in mature pollen grains collected from open flowers.

Chromosome-Pairing and Pollen Viability in Desmodium ovalifolium Wall × Desmodium heterocarpon (L) DC. Hybrids

Lack of genetic compatibility can result in low viable seed production in wide crosses. One year of an ongoing hybridisation program, during which 1333 Desmodium ovalifolium × Desmodium heterocarpon crosses were made, resulted in only two F1 plants. An examination of four stages of microsporogenesis (metaphase I, first division segregation, late tetrad microspore production, and pollen shed) was conducted for two lines of D. ovalifolium, three lines of D. heterocarpon and five D. ovalifolium × D. heterocarpon F1 hybrids made over a 2- year period. Both parental lines and hybrids had low levels of metaphase I univalents, anaphase I laggards, abnormal tetrad microspore production, and had high percentages of pollen stainability. Lack of chromosome homology does not appear to be the reason for low hybrid production in controlled crosses between D. ovalifolium and D. heterocarpon.

Developmental regulation of excision timing of Mutator transposons of maize: Comparison of standard lines and an early excision bzl::Mu1 line

AbstractThree characteristics of standard Mutator lines reflect developmental regulation: new mutants usually involve single gametes, somatic excision is restricted to terminal cell divisions during tissue development, and germinal excision is rare. By selection for earlier (larger) somatic sectors in the aleurone, a Mutator line was identified that exhibits a dramatic elevation in somatic excision frequency during the first three nuclear divisions of the endosperm and more than a 10‐fold increase in germinal reversion from the bzl::Mul reporter gene. The programming of early sectoring is dominant in crosses with Mutator lines containing diverse reporter alleles. Germinal reversion is biased 5‐ to 10‐fold for events through the pollen compared to the ear. The timing of germinal excision in the tassel is late because somatic excision sectors in the anthers are small; however, 98% of the germinal revertants are concordant. These observations indicate that in the early sectoring line Mu excision usually occurs before the mitotic divisions that separate gametic nuclei and may be restricted to the early stages of microsporogenesis. © 1992 Wiley‐Liss, Inc.

Structural studies of microsporogenesis in fertile and male-sterile onions (Allium cepa L.) containing the cms-S cytoplasm

The structure of anther tissues has been studied during microsporogenesis in male-sterile and -fertile onions. Three types of abnormal tapetal behaviour have been observed within the single line II/3ms containing the cms-S cytoplasm: type 1, the premature breakdown of the tapetum at the tetrad stage, type 2, the hypertrophy of the tapetum after the diad stage followed by its premature autolysis and, type 3, in which the tapetum remains in good condition but for an abnormally long period of time. Tapetal autolysis proceeds in the same manner in both male-steriles and -fertiles with only the stage at which it occurs differing between the types of plants. Mitochondria were prominent in the tapetal tissue of all onion types throughout all stages of microsporogenesis and were still visible during the last stages of tapetal autolysis. In a detailed study of type 2 behaviour, no differences in mitochondrial volumes were found until the tapetum hypertrophied.

T-URF 13 Protein from Mitochondria of Texas Male-Sterile Maize (Zea mays L.)

The protein T-URF13 (URF13) is specific to mitochondria of maize (Zea mays L.) with Texas (T) male-sterile cytoplasm and has been implicated in causing male sterility and susceptibility to T-cytoplasm-specific fungal diseases. T-URF13 was purified from isolated mitochondria from maize (line B73) with T cytoplasm by gel filtration and a quasi two-dimensional polyacrylamide gel electrophoresis system. Antibodies to the purified and denatured protein were produced in rabbits. Anti-T-URF13 antiserum was used to show that T-URF13 is in the inner membrane of mitochondria and behaves as an integral membrane protein when mitochondria are fractionated with sodium carbonate or Triton X-114. The antiserum and protein A tagged with 20-nanometer-gold particles were used to localize T-URF13 in T mitochondria by electron microscopy of sections of isolated mitochondria from etiolated shoots and sections of roots and of tapetal cells at pre-and post-degeneration stages of microsporogenesis. The microscopic study confirms that T-URF13 is specifically localized in the mitochondrial membranes of all of the T mitochondria tested, notably those in the tapetum from the meiocyte stage to the late-microspore stage. No change in the amount of labeled T-URF13 protein in the mitochondria of aging tapetal cells was detected.

Stamen-specific proteins of buffelgrass ( Cenchrus ciliaris)

Summary Total proteins were extracted from Cenchrus ciliaris L. (buffelgrass) pistils at the stages of megasporogenesis and of embryo sac enlargement and from anthdrs at the stages of microsporogenesis and of uninucleate microspore enlargement. They were analyzad by two-dimensional isoelectric focusing/SDSpolyacrylamide gel electrophoresis. Four stamen-specific proteins were detected. One of them was specific to the microsporogenesis stage and one to the uninucleate microspore stage. The other two were found in both stages. No pistil-specific protein was found among 300 spots examined. Two cultivars gave identical results. The stamen-specific proteins might be involved in sexual differentiation in this species or they could be gametophyte- or meiosis-specific proteins.

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.

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.

Ethidium Bromide-Induced Changes in Intensity of Ultraweak Photon Emission from Microsporocytes of Larch in Selected Stages of Development

Ethidium bromide-induced changes in intensity of ultraweak photon emission were investigated with the use of fractions of microsporocytes in successive stages of microsporogenesis separated from the male cones of Larix decidua Mil. The results seem to point to the possible involvement of DNA in the process of ultraweak photon emission, but other facts that may also account for the observed changes of emission intensity are in addition considered in this paper.

Maize microsporogenesis

The use of maize (Zea mays L.) pollen for basic scientific research has been well documented, but the progression of clear cytological features of maize microsporogenesis has not been fully documented. This study was undertaken to identify cytologically the different developmental stages of maize pollen and to correlate them with morphological features of the developing maize tassel. Morphological changes in the length of the tassel, floret, and anther were recorded and correlated with six cytologically defined stages of microsporogenesis: premeiosis, meiosis, uninucleate stage, first pollen mitosis, second pollen mitosis, and mature pollen.Key words: cytogenetics, gametophyte, maize, microsporogenesis, pollen.

Characterization of cytoplasmic male sterility in Petunia hybrida and Zea mays. Localization and activity of cytochrome c oxidase

Anthers of male fertile, cytoplasmic male sterile (cms), and restored male fertile Petunia hybrida, are analyzed for cytochrome c oxidase (cox) activity in subsequent stages of microsporogenesis, and compared with anthers of male fertile, cms-S and cms-C Zea mays. The cox activity is determined in anther extracts and cytochemically. In petunia anthers, the first differences in cox activity occur from meiosis onward. However, at these stages, the initial symptoms of degeneration are already apparent. It is suggested that the decline in enzyme activity of the cms petunia anthers is the result rather than the cause of the non-formation of functional pollen. In maize anthers, the cox activity of sterile-type anthers is reduced in comparison with fertile-type anthers from premeiosis onward. There are also consistent cytochemical differences in the mitochondrial organization of cox activity between pollen of cms-S and male ferile maize anthers. In fertile-type mitochondria, the DAB reaction product indicating cox activity is localized in the cristae and within the space between the outer and inner limiting membranes of the organelles. In mitochondria of pollen of cms-S maize, cox activity is only observed between the outer and inner membranes of the mitochondria. The biochemical and cytochemical differences are observed at stages of development at which no structural signs of degeneration are apparent. The results suggest that cms in maize correlates with deviations in cytochrome c oxidase activity.

Interchange polymorphism in natural populations of Allium paniculatum L. (Liliaceae): nature, frequency, effects, and mechanism of maintenance

A reciprocal translocation was found with a high frequency (average 44.44%) in four natural populations of Allium paniculatum L. (Liliaceae) from the South of Spain. The chromosomes involved are 1 and 7. The translocation is reciprocal and unequal. Chiasma frequency in the chromosomes not involved in the interchange is not affected, but chiasma frequency is decreased in the translocated chromosomes in the heterozygotes. As a satellite chromosome is involved in the interchange, the nucleolus is associated with the quadrivalent and the pattern of nucleolus formation is changed in heterozygotes, which have a lower mean number of nucleoli [Formula: see text] than homozygous standard individuals [Formula: see text]. The spontaneous mutation rate for interchanges during the early stages of microsporogenesis is high (μ = 1.08 × 10−2). No interchange homozygotes were found in any of the four populations analyzed. Furthermore, a comparative analysis of heterozygous (HT) and homozygous standard (HM) individuals in two populations demonstrated that homozygous standard plants show, on the whole, higher fitness than the heterozygotes. This can be attributed to a greater egg cell fertility and seed set. The possible causes of maintenance are discussed: the interchange in A. paniculatum is probably not maintained by overdominance for generative reproductive characters, nor by a mutation–selection equilibrium. One possibility, that heterozygotes have superior vegetative reproduction, still remains open for future investigation.Key words: Allium paniculatum, interchange polymorphism, fitness.

Development of Tapet urn and Microspores in Canna L.: an Example of an Invasive but Non-syncytial Tapetum

An investigation of microsporogenesis in Canna L. revealed that the tapetum is invasive but non-plasmodial. Tapetai cell protoplasts are released as individuals. In the loculus they are at first more or less spherical but can produce amoeboid processes in late stages of microsporogenesis. They do not fuse with one another. Meiosis is normal and cytokinesis is successive. The implications of the novel type of tapetum are discussed.

Microsporogenesis in a Parthenogenetic Species, Houttuynia cordata Thunb. (Saururaceae)

Microsporogenesis in the parthenogenetic species Houttuynia cordata Thunb. (Saururaceae) was studied microscopically. Cytokinesis failure after meiosis results in the formation of coenocytic microspores that show a wide range of variation in shape and size. Although tapetal cells do not show any demonstrable abnormalities, the microspores degenerate at the vacuolate microspore stage some time after dissolution of the callose. At the last stage of microsporogenesis, ghosts of the coenocytic microspores, which consist of only ektexine, remain in the loculus. The species is completely, or nearly completely, male-sterile.

Characterization of cytoplasmic male sterility in Petunia hybrida. I. Localization, composition and activity of esterases

Anthers of male fertile, cytosterile and restored male fertile clones of Petunia hybrida were compared for esterase activity and composition in subsequent stages of microsporogenesis. Three methods were applied (i) ultra-thin layer isoelectric focussing on polyacryl amide gels, (ii) quantitative spectrophotometrical assay, (iii) histochemical determination of total esterase activity associated to the azo-coupling method (Pearse, 1972). In male fertile and restorer idiotypes the isozyme patterns were quite similar. Both the number and intensity of bands increased gradually till the tetrad stage. In contrast, esterase activity in cytosterile anthers remained at a low level and hardy any new bands showed up in later stages. This unvariable, low activity level in cytosterile anthers was also found in the spectrophotometric assay. Histochemical determinations revealed that in male fertile anthers esterase activity is concentrated in the outer tapetal layer at late prophase and that it accumulates there till the early microspore stage. In male sterile anthers esterase accumulation in the tapetal cells stops at the moment that tapetal breakdown becomes visible. This suggests that differences in esterase activity and composition are an effect rather than a cause of the failing pollen formation.

Some Effects of Temperature and Light on Floral Initiation and Development in Acacia pycnantha

Floral initiation and development in Acacia pycnantha were studied under three environments. Two had ambient southern Australian temperatures of warm summer (mean max. 32°C, mean min. 16°C) and cool winter (mean max. 19°C, mean min. 8°C), one with full sunlight (outside) and the other with 30% light intensity (shadehouse). The other environment (glasshouse) had slightly lower than normal light intensity and a relatively constant year round temperature of mean 28°C maximum and 16°C minimum. Plants were scored for microscopic and macroscopic evidence of floral initiation and development. Floral primordia were initiated all year round under all environments. Floral development proceeded normally under ambient conditions of temperature and light, and anthesis occurred between August and October. Under low light intensity, floral development did not progress beyond a very early stage and macroscopically visible racemes were rare. Under the constant temperatures, floral development proceeded normally up to the stage of microsporogenesis and megasporogenesis. Meiosis did not occur and inflorescence buds ceased growth and were shed from the plant. Plants were transferred between the outside and glasshouse conditions in June, at around the stage of meiosis. Those transferred from outside to the glasshouse did not flower whereas some of those transferred from the glasshouse to outside flowered, but later and for a shorter period than plants maintained outside throughout. It appears that a 70% reduction in sunlight inhibits floral development at an early stage and that temperatures of approximately mean maximum 19°C and minimum 8°C are required for meiosis in Acacia pycnantha.

An ultrastructural study of particle distribution during microsporogenesis in tomato plants infected with the Brazilian tobacco rattle virus

Long and short particles of the Brazilian tobacco rattle virus (BTRV) were visualized in cells of the anther tissues of infected tomato plants. The BTRV appeared mostly as aggregates of parallel particles associated with mitochondria, though isolated aggregates and individual particles were seen in microspores and mature pollen grains. The BTRV particles could be seen in the cytoplasm of infected anther cells during the various stages of microsporogenesis from the stage of premeiotic cells to mature pollen grains. Virus distribution through meristems is the main mechanism that permits the BTRV to reach the pollen. Virus passage from somatic cells to the microspore-precursor cells while plasmodesmata are still functional may be complementary in case of early infection or the only way of access in late-infected plants. Both short and long particles could be seen in the cytoplasm of the vegetative and generative cells of the pollen. No virus particle was ever seen in the nuclei of infected cells, associated with the cellulose or callose walls, or on the outside wall of pollen grains. There was a small number of virus particles present in the microspore mother cells and microspores, and a large number of short- and long-particle aggregates in the mature pollen grains. These results indicate that virus increase occurs during pollen grain maturation and is not only the result of distribution. Microsporogenesis is comparable between infected and noninfected tissues. However, pollen grains from infected plants showed a lower germination than normal pollen.

Ribulose Bisphosphate Carboxylase Activity in Anther-Derived Plants of Saintpaulia ionantha Wendl. Shag

Plants obtained from anther culture of the African violet, Saintpaulia ionantha Wendl. ;Shag' and vegetatively cloned copies of the parent anther donor plant were examined for their ploidy and ribulose-1,5-biphosphate carboxylase (RuBPcase) activity. The cloned parent plants were all diploid and did not vary much in their nuclear DNA, chlorophyll, and RuBPcase activity. Some of the anther-derived plants were similar to the parent plants while others were not. Different levels of ploidy were observed among the androgenetic plants. RuBPcase activities higher than that of the parent plants were found in some anther-derived plants. However, there was no direct correlation between ploidy and RuBPcase activity. Expression of nuclear genes from a single parent in the anther-derived plants and it's diploidization or plastid changes during early stages of microsporogenesis or androgenesis are suggested as possible reasons for the variations observed among them. This could be a useful technique to obtain physiological variants which could be agronomically desirable.

The cytological effects of the gametocides Ethrel and RH‐531 on microsporogenesis in barley (Hordeum vulgare L)

Abstract. Barley plants (Hordeum vulgare L. cv. Midas) raised under controlled environmental conditions were sprayed with either of the gametocides Ethrel and RH‐531. At various times after spraying the anthers were fixed for light and electron microscopy. Abortion of sporogenous cells occurred in plants sprayed at both pre‐ and post‐meiotic stages of microsporogenesis. In contrast, cells of the tapetum were insensitive to the immediate effects of gametocides. The cytological effects of the gametocides are similar to those induced by male sterile genes in a variety of plants. These range from the induction of additional mitotic divisions in the pollen mother cells to exine malformations on developing microspores. These observations are discussed in terms of the control mechanisms operating during microsporogenesis.