Mature Gametophytes Research Articles

Cytological studies on the regenerating mature female gametophyte of Taxus baccata L. and mature endosperm of Tilia platyphyllos Scop. in the in vitro culture

Cytological studies on the regenerating mature female gametophyte of Taxus baccata L. and mature endosperm of Tilia platyphyllos Scop. in the in vitro culture

Floral morphology and embryology of Helwingia (Helwingiaceae, Aquifoliales): systematic and evolutionary implications.

Helwingia, a shrub or small tree of four species distributed in East Asia, has been assigned to various families, mainly Cornaceae. However, molecular analyses show that the genus belongs to its own family Helwingiaceae which is sister to Phyllonomaceae (Phyllonoma only) in the order Aquifoliales. On the basis of H. japonica, we investigated the poorly understood floral and embryological characters of Helwingia, and compared their features with those of other Aquifoliales, particularly those of Phyllonomaceae. Results showed that perianth leaves of Helwingia represent sepals, because in plesiomorphic pentamerous flowers, they agreed in position with sepals (not with petals) in pentamerous flowers of Phyllonoma. Overall comparisons based on available information show that, while sharing with Phyllonoma the epiphyllous inflorescence, the inferior ovary, and an epigynous disc nectary as syapomorphies, Helwingia is characterized by loss of petals, obhaplostemony, large recurved stigmas, poorly developed disc nectary, tenuinucellate ovules with a mature female gametophyte filled with densely stained cytoplasm, and a thin mature seed coat. Morphological evidence, like molecular evidence, confirms that Helwingia is sufficiently distinct to be placed in its own family. Morphological and field observations suggest wind and insect pollination in H. japonica, which is the first example of ambophily in Aquifoliales.

Temperature requirements for growth and maturation of the warm temperate kelp Eckloniopsis radicosa (Laminariales, Phaeophyta)

SummaryThe annual kelp Eckloniopsis radicosa is distributed along Japanese coasts and occurs within the area with a February isotherm ranging 15–18°C and August isotherm ranging 25–28°C. In this study, the effects of temperature on the gametophyte growth and maturation, and the young sporophyte growth of E. radicosa were examined and the results are discussed in relation to the distribution of other warm‐adapted kelp species and the potential effects of climate change. The optimal temperature ranges for growth of male and female gametophytes were 23–27°C and 20–26°C, respectively. The upper survival temperature for gametophyte growth was 31°C for males and 30°C for females, respectively. The optimal temperature range for maturation of female gametophytes was ≤23°C. The optimal temperature range for growth of young sporophytes was 14–22°C. It was clarified that E. radicosa has the most warm‐adapted characteristics for growth and maturation of gametophytes among members of the Laminariales studied so far. The natural seawater temperature ranges during the growth and maturation seasons for gametophytes of E. radicosa, as well as the growth season for young sporophytes near to the northern and southern distribution limits (Izu‐Oshima: 14.9–24.5°C, Ichiki‐kushikino: 17.1–29.6°C), agreed with the experimentally determined temperature requirements. The warm‐adapted gametophyte stage and annual lifecycle are major factors enabling survival of E. radicosa in warm waters near tropical regions along the Japanese coast.

Beyond antheridiogens: chemical competition between gametophytes ofPolypodium appalachianumandPolypodium virginianum

To understand the mechanisms by which fern gametophytes compete and the consequences of their interactions, we studied the effects of intraspecific and interspecific chemical competition on spore germination, sexual development, and gametophyte size in two closely related and co-occurring species of Polypodium from eastern North America. We cultured gametophytes of diploid Polypodium appalachianum Haufler & Windham and tetraploid Polypodium virginianum L. and recorded spore germination, sexual development, and gametophyte size and growth rates in a series of treatments representing different levels of competition within and between the two species. We found that mature gametophytes of both species reciprocally inhibit spore germination, sexual development, and growth of neighboring plants; we show that these effects are due to chemical interactions and not competition for resources. Competitive effects on spore germination and sexual development are similar for within- and between-species interactions, but repression of growth and gametophyte size is greater when competing gametophytes are heterospecific. An additional mechanism of intergametophytic competition via proliferous vegetative growth is also reported. We conclude that gametophytes of these species interact through a novel context-dependent chemical system that is independent from sex expression-regulating pheromones (antheridiogens). Our findings indicate that inhibition of growth and development among fern gametophytes is not solely a side effect of antheridiogens, as is generally thought.

Proteomic approaches to sexual development mediated by antheridiogen in the fern Blechnum spicant L.

This report is intended to compare proteomic profiles between female and male gametophytes of Blechnum spicant L. For this purpose, female gametophytes were obtained from spores germinated on Murashige and Skoog medium (1962), and the male ones by culturing 30-day-old gametophytes on the same medium supplemented with extract derived from mature gametophytes, which exhibits anteridiogen effect. Proteins were extracted using the phenolic method, and after two-dimensional gel electrophoresis, 581 spots were detected in Coomassie stained gels within the 3-11 pH range and 10-100 kDa Mr ranges. Quantitative and qualitative differences in spot intensity between both types of gametophytes were found. The induction of male gametophytes by antheridiogens was correlated to a global increase in stress and defence-related pathways, which affect flavonoid signaling and cell division, while reducing protein biosynthesis, photosynthesis, and other energy-related pathways, reflecting how stressed are the gametophytes during the induction process. This is the first proteomic study that examines proteins associated to sexual development in the gametophyte of the fern B. spìcant.

Asexual reproduction and protonemal development in vitro in Fontinalis antipyretica Hedw.

As sporophytes are very rare and asexual propagules unknown it is generally assumed that the moss Fontinalis antipyretica spreads almost exclusively via detached shoots carried in water currents. This study of regeneration in vitro reveals that F. antipyretica produces a variety of filament systems originating from virtually every part of the gametophyte, including: cortical cells in the bases of detached shoots, the margins and abaxial surfaces of leaves, stems following leaf removal and the laminae of detached leaves. The filaments vary from protonemata comprising short rectangular cells with transverse cross-walls to unbranched rhizoids. Filamentous gemmae, liberated by schizolysis, and spherical brood cells are produced in ageing and desiccating cultures. In nature these asexual propagules are probably produced in response to falling water levels and may have an important and hitherto unsuspected role in the spread and spatial genetic structure of F. antipyretica. In F. antipyretica the high level of phenotypic plasticity, that characterizes the mature gametophytes of aquatic bryophytes, also extends to the filamentous phase in the life cycle. Major differences between axenic and contaminated cultures are likely due to positive associations between the moss and bacterial and/or fungal contaminants.

English

Cyathea spinulosa Wall. ex Hook. is a type genus of Cyatheaceae family. It is listed in endangered category of IUCN Red Data Book and also placed in Convention on International Trade of Endangered Species of Flora and Fauna (CITES) Appendix II. The spore germination, gametophyte morphogenesis and sporophyte rooting of Cyathea in response to 2.0% sucrose and three major growth hormones: Indole–3 acetic acid (IAA), indole–3 butyric acid (IBA) and naphthalene acetic acid (NAA) was studied. The study was carried out at the tissue culture laboratory of Central Department of Botany, Tribhuvan University, Nepal. The spore of Cyathea was reared on Knop’s Basal Medium (KBM) with 2.0% sucrose after surface sterilization. The sporophyte was sub-cultured on medium with growth hormones IAA, IBA and NAA, each containing 1, 2 and 3 ppm concentrations. The study suggested that Cyathea exhibited bipolar germination and the gametophyte development was Adiantum type. The mature gametophyte was observed as heart shaped. Sex organs were not observed up to 24 weeks which indicates the development of apogamous sporophyte. The growth hormones affect the development of leaves and roots. The sporophyte containing three leaves and two roots was the best result obtained in KBM containing 1 ppm IAA.   Key words: Cyatheaceae, Cyathea spinulosa, morphogenesis, Knop’s medium, growth hormones, apogamous sporogophyte.

Central cell degeneration leads to three-celled female gametophyte in Zeylanidium lichenoides Engl. (Podostemaceae)

The absence of double fertilization and lack of endosperm formation are key embryological features of Podostemaceae, which is unique among the angiosperms. Double fertilization fails in spite of the fact that two male gametes are carried in the pollen tube and the incipient embryo sac is equipped with an egg cell and a central cell. Little is known about the proximate causes of the failure of double fertilization. The female gametophyte of Zeylanidium lichenoides, (subfamily — Podostemoideae) has a monosporic mode of development resulting in an initial four-celled/four-nucleate condition. However, the central cell degenerates before the arrival of the pollen tube in the vicinity of micropyle, thus the mature and functional female gametophyte of Z. lichenoides is ontogenically a three-celled/three-nucleate structure. It is inferred that the formation of a highly reduced female gametophyte, presumably is a result of degeneration of the central cell.

Gametophytic phase of two Neotropical ferns, Dennstaedtia globulifera (Poir.) Hieron and Hypolepis poeppigii Mett. ex Maxon (Dennstaedtiaceae)

This study aimed to provide a detailed description of the gametophyte morphology of two Neotropical ferns, Dennstaedtia globulifera and Hypolepis poeppigii, including spore germination, gametophytic development, and mature gametophyte morphology. Spores were sown in Petri dishes with Dyer medium. Petri dishes were kept in environmental room with a light regime of eight light-hours per day. We document the described morphologies through scanning electron microscope photomicrographs and light microscopy. Germination of spores follows the Vittaria type and the gametophytic development follows the Adiantum type. The adult gametophytes are cordiform or ameristic, unisexual and glabrous. Archegonia emerge from below the notch, and have four rows of cells, each with four, rarely five, cells and necks bent toward the roots. Antheridia are found among the roots, on the abaxial surface and margin of the laminar gametophyte, and have three cells; dehiscence of the antheridia is produced through formation of a pore. D. globulifera has simple antheridia, whilst H. poeppigii has individual antheridia or antheridia grouped on a single or multi-celled antheridiophore. The antheridiophore is described for the first time.

Understanding mechanisms of rarity in pteridophytes: Competition and climate change threaten the rare fern Asplenium scolopendrium var. americanum (Aspleniaceae)

Understanding the ecology of rare species can inform aspects of conservation strategies; however, the mechanisms of rarity remain elusive for most pteridophytes, which possess independent and ecologically distinct gametophyte and sporophyte generations. To elucidate factors contributing to recent declines of the rare fern Asplenium scolopendrium var. americanum, we studied the ecology and ecophysiology of its gametophyte generation, focusing on responses to competition, temperature, and water stress. Gametophytes of A. scolopendrium var. americanum, its widespread European relative A. scolopendrium var. scolopendrium, and five co-occurring fern species were grown from spores. Gametophytes were grown at 20°C and 25°C, and germination rates, intra- and interspecific competition, desiccation tolerance, and sporophyte production were determined for all species. Gametophytes of A. scolopendrium var. americanum had the lowest rates of germination and sporophyte production among all species studied and exhibited the greatest sensitivity to interspecific competition, temperature increases, and desiccation. Mature gametophytes of A. scolopendrium var. americanum grown at 25°C were 84.6% smaller than those grown at 20°C, and only 1.5% produced sporophytes after 200 d in culture. Similar responses were not observed in other species studied. The recent declines and current status of populations of A. scolopendrium var. americanum are linked to its gametophyte's limited capacity to tolerate competition and physiological stress linked to climate change. This is the first study to develop a mechanistic understanding of rarity and decline in a fern and demonstrates the importance of considering the ecology of the gametophyte in plants with independent sporophyte and gametophyte generations.

Gametophyte Morphology and Development of Three Species ofCyrtogonellumChing (Dryopteridaceae)

Abstract Gametophyte morphology and development of three species of Cyrtogonellum Ching (Dryopteridaceae) were described with the aim to increase our knowledge on the gametophytic stage of this fern genus especially the occurrence of sexual structures. Spore germination followed the Vittaria-type development, whereas prothallus growth followed the Aspidium-type development. Unicellular glandular hairs were located on both margins and surface of the prothalli. The heart-shaped prothalli of C. caducum showed irregularly lobed margins with multicellular filamentous to wing-like extensions. One to several agamously formed embryos were found on a single mature gametophyte of C. inaequale but only one of these developed into a mature sporophyte. Young sporophytes possessed scales with one to several glandular cells. Antheridia were found in all three species, but archegonia were observed only on mature prothalli of C. fraxinellum, which were always located near the midrib of the cordate-thalloid prothallus. The...

Polar nuclei behaviour in the mature megagametophyte of the natural tetraploid Trifolium pratense (Fabaceae)

The mature female gametophyte in Trifolium pratense L., a natural tetraploid plant, consists of 7 cells: the egg cell, 2 synergids, the central cell, and 3 antipodal cells. This type of mature female gametophyte is known as polygonum. The central cell occupies the largest portion of the mature female gametophyte and the polar nuclei are situated close to the egg apparatus. The cytoplasm of the central cell is rich in organelles. A large number of rough and smooth endoplasmic reticulum, mitochondria, plastids, dictyosomes, ribosomes, starch, and lipid bodies were observed. Differences were identified in this plant between the sizes of polar nuclei and secondary nuclei generated by the fusion of the former. It was observed that the polar nuclei had fused long before the pollen tube entered the female gametophyte, and that the secondary nuclei in some female gametophytes were degenerated before fertilisation.

Gene expression associated with apogamy commitment in Ceratopteris richardii

Apogamy is a phenomenon in which a sporophyte develops asexually, directly from a cell or cells of a gametophyte. It is a phenomenon described mainly in lower plants, but shares certain aspects with apomixis in angiosperms. The genes involved in apogamy commitment in ferns are unknown. We hypothesize that the mechanism of asexual reproduction is controlled in lower and higher plants by overlapping sets of genes. To this end, we created a normalized subtracted cDNA library that represents genes with increased expression during apogamy commitment in the fern Ceratopteris richardii. The cDNA library consists of 170 unique sequences. Compared to the mature gametophyte transcriptome of the fern Pteridium aquilinum, the apogamy library is enriched in plant GO-Slim terms that are associated with stress and metabolism. In silico expression analyses of the closest Arabidopsis homologs of the apogamy library revealed many genes that display preferential expression in seed and flower tissues, structures that are absent in ferns. This apogamy library provides a rich resource for investigations into the genetic control of apogamy in ferns and comparisons with the asexual processes of higher plants.

Gametophyte Development of Pteris biaurita and Effects of Its Antheridiogen on the Gametophyte Development of Ceratopteris thalictroides

The gametophyte development of the fern Pteris biaurita and the effects of antheridiogen secreted by the mature gametophyte of P.biaurita on the spore germination and gametophyte development of Ceratopteris thalictroides in darkness and light conditions were investigated.The results indicated:(1) The spores are dark brown,trilete.The spore germination is of the Vittaria type.The pattern of the prothallial development belongs to the Ceratopteris type.No trichome is produced during the gametophyte development.It is discovered that the gametophytes of P.biaurita can produce antheridia but can not produce archegonia in any cultural conditions.When the sowing density was appropriate,apogamous reproduction occurred in the mature gametophyte.(2) In light condition,the antheridiogen of P.biaurita could promote the spore germination of Ceratopteris,but in dark condition,the antheridiogen inhibited the spore germination of Ceratopteris.However,the effect of either promotion or inhibition was not significant.(3) In light condition,the antheridiogen of P.biaurita could delay the formation of the notch of gametophyte(i.e.the meristem) of Ceratopteris.However,it had no significant effect on the morphology and sex differentiation of gametophyte.In dark condition,the antheridiogen of P.biaurita exhibited significant effects on the morphological development of Ceratopteris.The gametophyte of Ceratopteris in the dark condition produced well developed meristem in contrast to the control materials.However,it exhibited no significant effect on the sex differentiation of gametophyte of Ceratopteris.It can be concluded that the antheridiogen system in the fern P.biaurita may greatly differs from that in the fern Ceratopteris.

The Effects of Water Temperature on Growth and/or Maturation of Gametophytes and Juvenile Sporophytes of Ecklonia cava and E. kurome (Laminariales, Phaeophyta) growing in the Coasts of Wakayama Prefecture

The Effects of Water Temperature on Growth and/or Maturation of Gametophytes and Juvenile Sporophytes of Ecklonia cava and E. kurome (Laminariales, Phaeophyta) growing in the Coasts of Wakayama Prefecture

Expression dynamics of metabolic and regulatory components across stages of panicle and seed development in indica rice

Carefully analyzed expression profiles can serve as a valuable reference for deciphering gene functions. We exploited the potential of whole genome microarrays to measure the spatial and temporal expression profiles of rice genes in 19 stages of vegetative and reproductive development. We could verify expression of 22,980 genes in at least one of the tissues. Differential expression analysis with respect to five vegetative tissues and preceding stages of development revealed reproductive stage-preferential/-specific genes. By using subtractive logic, we identified 354 and 456 genes expressing specifically during panicle and seed development, respectively. The metabolic/hormonal pathways and transcription factor families playing key role in reproductive development were elucidated after overlaying the expression data on the public databases and manually curated list of transcription factors, respectively. During floral meristem differentiation (P1) and male meiosis (P3), the genes involved in jasmonic acid and phenylpropanoid biosynthesis were significantly upregulated. P6 stage of panicle, containing mature gametophytes, exhibited enrichment of transcripts involved in homogalacturonon degradation. Genes regulating auxin biosynthesis were induced during early seed development. We validated the stage-specificity of regulatory regions of three panicle-specific genes, OsAGO3, OsSub42, and RTS, and an early seed-specific gene, XYH, in transgenic rice. The data generated here provides a snapshot of the underlying complexity of the gene networks regulating rice reproductive development.

Developmental events in ovules of the ornamental plant Rudbeckia bicolor Nutt

Microscopic observations of R. bicolor ovules showed that tetrasporic embryo sacs of Fritillaria type are formed. In the mature female gametophytes modifications in antipodal cell formation and egg apparatus organization were observed, e.g. morphological resemblance was evident of antipode or synergid to the egg cell. In the central cell cytoplasm of the mature gametophytes the presence of small bodies was a characteristic feature. Development of both embryo and endosperm was observed in ∼73% of ovules at the embryo stage, while retarded or arrested development of the endosperm was found in ∼26% of them. Occasionally, two embryos occurred in the embryo sac. This is the first record of polyembryony in this species. Although hemigamy has been previously described in Rudbeckia bicolor Nutt., in the present investigations mosaic structure of embryos was not detected. Measurements of the C-DNA amount (flow cytometry) revealed embryo nuclei with 2C DNA content only, and endosperm nuclei with 5C DNA content in the mature seeds. No peak corresponding to 1C nuclei was detected in the histograms obtained from the nuclear preparation of seeds or seedling parts. These results suggest that hemigamy is not an obligatory phenomenon in R. bicolor. The mean 2C DNA value was determined as 14.51 pg (the first estimation for this species).

The Gametophyte of Ophioglossum pendulum in Culture

Abstract The spores of Ophioglossum pendulum ssp. falcatum germinated after six weeks in the dark on a nutrient medium containing inorganic nutrients and glucose. The gametophytes grew on the same nutrient medium to give globular, teardrop-shaped, and finally cylindrical gametophytes. The mature gametophytes were cylindrical and highly branched. Other aspects of these gametophytes were normal for Ophioglossum gametophytes with sunken antheridia and short-necked archegonia. The gametangia were functional because fertilization took place in older cultures. Mature gametophytes of O. pendulum ssp. falcatum from culture had the same structure as those of O. pendulum ssp. pendulum from nature. The differing conditions under which the gametophytes of both subspecies grew did not alter their stellate form.

Gametophyte and sporophyte of tree ferns in vitro culture

Experiments had been carried out on gametophytes and very young fronds of sporophytes with application of Murashige and Skoog (1962) medium. The paper described the results of 15 years in vitro experiments on 16 species of tree ferns belonging to various genera: <em>Blechnum</em>, <em>Cibotium</em>, <em>Cyathea</em> and <em>Dicksonia</em>. Genus <em>Cyathea</em> was represented by: <em>C. australis</em> (R.Br.) Domin., <em>C. capensis</em> (L.f.) Sm., <em>C. cooperi</em> (F.Muell.) Domin, <em>C. brownii</em> Domin, <em>C. dealbata</em> (G.Forest) Sw., <em>C. dregei</em> Kunze, <em>C. leichhardtiana</em> (F.Muell.) Copel., <em>C. robertsiana</em> (F.Muell.) Domin., <em>C. schanschin</em> Mart., <em>C. smithii</em> Hook.f. and <em>Cyathea</em> sp. In case of genus <em>Dicksonia</em> only two species were introduced into our experiments: <em>D. fibrosa</em> Colenso and <em>D. sellowiana</em> Hook.. Taxa <em>Blechnum</em> was presented by <em>B. brasiliense</em> Desv. and <em>Cibotium</em> by <em>C. glaucum</em> (Sm.) Hook. and Arn. and <em>C. schiedei</em> Schltdl. and Cham.. The studied species presented various responses on culture conditions depending on the level of stage of development. Time required for spores germination differed between species and took from only a few to 16 weeks. Prothalium formations showed various types of growth presented by marginal meristems. For all investigated species long term gametophyte in vitro cultures was established. Mature gametophyte possessed functional antheridia and archegonia. Spontaneous fertilization helped to establish the culture of young sporophytes. For all species the ex vitro culture in greenhouse collection was established. Manipulation of sucrose content in the medium stimulated the multiplication of gametophytes, but its lack induced formation of gemmae. Apospory was observed when culture of very young fronds was extended for 6 months and new generation of gametophytes was developed. Finally, sporophytes of 12 species were obtained and they have been growing in our greenhouse.

Effects of Nitrate and Phosphate on the Growth and Maturation of Gametophytes of Laminaria religiosa

Effects of Nitrate and Phosphate on the Growth and Maturation of Gametophytes of Laminaria religiosa