Formation Of Reproductive Cells Research Articles

How did Mendel arrive at his discoveries?

There are few historical records concerning Gregor Johann Mendel and his work, so theories abound concerning his motivation. These theories range from Fisher's view that Mendel was testing a fully formed previous theory of inheritance to Olby's view that Mendel was not interested in inheritance at all, whereas textbooks often state his motivation was to understand inheritance. In this Perspective, we review current ideas about how Mendel arrived at his discoveries and then discuss an alternative scenario based on recently discovered historical sources that support the suggestion that Mendel's fundamental research on the inheritance of traits emerged from an applied plant breeding program. Mendel recognized the importance of the new cell theory; understanding of the formation of reproductive cells and the process of fertilization explained his segregation ratios. This interest was probably encouraged by his friendship with Johann Nave, whose untimely death preceded Mendel's first 1865 lecture by a few months. This year is the 200th anniversary of Mendel's birth, presenting a timely opportunity to revisit the events in his life that led him to undertake his seminal research. We review existing ideas on how Mendel made his discoveries, before presenting more recent evidence.

Different Dynamics of Reproductive Cell Development in Oviparous Clausilia bidentata and Ovoviviparous Ruthenica filograna Snails.

Most terrestrial snails are oviparous and only some are ovoviviparous. The physiology of the reproductive system and its activity in these two groups have received little attention. We compared the month-to-month dynamics of reproductive cell formation between two species of Clausiliidae snails: Ruthenica filograna (an ovoviviparous species) and Clausilia bidentata (an oviparous species). Our aim was to test the hypothesis that the seasonal activity of gametogenesis is determined by reproductive strategy (oviparity /ovoviviparity). The results showed that the frequency and number of reproductive cells in different stages varied month-to-month, within each species, and between the two species. Ruthenica filograna maintained its reproductive activity throughout the entire observation period, whereas the gonadal activity of C. bidentata changed with the seasons (it was temperature dependent). Our results are in tune with the hypothesis of Baur, that ovovivipary has some advantage over oviparity under harsher environmental conditions.

ADVANCES IN OIL PALM BREEDING: ISSUES AND CHALLENGES

Oil palm is the most efficient oil-bearing crop. However, its breeding cycle per generation requires at least a decade of meticulous work. In Malaysia, land under oil palm cultivation has increased by more than 50 per cent over the past 20 years. Price fluctuation in crude palm oil and fertiliser, further shrinkage of arable land and extreme labour shortage have propelled the demand for good quality planting materials as well as good crop management. Breeding plays a crucial role in providing good quality planting materials to boost the production of a crop. The first essential step in oil palm breeding is to choose a good parental combination that has high probability of generating offsprings with desired characteristics. Oil palm breeding requires massive resources. Field trials require large areas for extensive progeny testing to estimate their breeding values. Moreover, data collection of yield records, bunch analysis, and vegetative measurements, is labour-intensive. Since a breeder has limited control over environmental factors that affect genetic response, it is important for selection to be conducted on limited superior parents to achieve manageable populations in order to generate good quality materials. Breeders have been selecting palms based on their visible or measurable traits. Segregation occurs among offsprings as a result of the separation of the allele pairs encoding desired traits in each parent during the formation of reproductive cells. Therefore, selection may be imperfect as genotypic selection is largely overlooked. Hence, palms with visible desirable agronomic trait will be retained whereas crosses with good genetic diversity may be discarded. Phenotyping is a crucial step in generating information required by breeders to make selection. However, conventional phenotyping is labour-intensive, time-consuming and costly. Advancement in geo-informatics and imaging techniques allows high-throughput non-destructive phenotype data collection for quantitative studies of complex traits. Application of these technologies in oil palm breeding will accelerate the introduction of improved planting materials in a shorter time. Keywords: Oil palm, breeding, phenotyping, technology application, biotechnology.

Analysis of Meiotic Chromosome-Associated Protein Dynamics Using Conditional Expression in Budding Yeast.

The visualization of meiotic chromosomes and their associated protein structures in both wild-type and mutant cells adds valuable insight into the molecular pathways that underlie reproductive cell formation. Here we describe basic methodology for visualizing meiotic chromosomes in a long-standing model organism for investigating the molecular and cell biology of meiosis, the budding yeast, S. cerevisiae. This chapter furthermore highlights a variety of conditional expression regimes that can be used to understand the dynamics and/or developmental constraints of chromosomal protein structures; such dynamic aspects of the macromolecular structures that mediate meiotic chromosome biology are typically not obvious from standard protein visualization experiments.

GAS CHROMATOGRAPHY-MASS SPECTROMETRY ANALYSIS AND ANTIOXIDANT ACTIVITY OF PUNICA GRANATUM L. PEELS AND ITS ROLE AS IMMUNOSTIMULANT AGAINST SCHISTOSOMA MANSONI INFECTION IN BIOMPHALARIA ALEXANDRINA

ABSTRACTObjective: To evaluate the antioxidant activity and chemical composition of Punica granatum L. and test it as immunostimulants against Schistosomamansoni infection to Biomphalaria alexandrina snails.Methods: Antioxidant activity was evaluated by measuring the free radical scavenging activity of the 90% defatted methanol extract (90% DM)of P. granatum peels and its sub-derived fractions was evaluated via 2,2’-diphenyl-1-picrylhydrazyl and its chemical constituents were identified viagas chromatography-mass spectrometry (GC-MS) analysis. B. alexandrina snails were exposed to pomegranate extracts (PEs) for 1 month before theirchallenging with S. mansoni miracidia. Infection rates, immunological and histological parameters were, then, evaluated in PE-exposed snails andcompared to controls.Results: The antioxidants activities of PE, expressed as scavenging concentration at 50%, were in the following order; 90% DM (12.45) ˃n-butanol(15.59) ˃ethyl acetate (21.36) ˃water (49.16) µg/ml, compared to 7.50 µg/ml for ascorbic acid. The infection rates of PE-exposed snails were 20%,50%, 60%, 70%, and 80%, respectively, for 90% DM, n-butanol, ethyl acetate, water, and dichloromethane extracts compared to 95% in control snails.The number of amoebocytes showed a significant increase, clear differentiation, and size increment in exposed snails compared to controls. Moreover,hermaphrodite glands histology shows a full maturity in the formation of reproductive cells in PE-exposed snails. The GC-MS analysis of the 90% DMextract revealed the presence of 36 compounds representing 93.1% of the total composition. Piperidin-4-ol, 1,3-dimethyl-2,4,6-triphenyl (19.87%),and 6,11-dihydroxy-5,12 naphthacenequinone-1-carboxylic acid (7.80%) were the major components.Conclusion: The identified compounds in 90% DM extract of P. granatum may be responsible for the high antioxidant activity of the fruit and it mayaccount for its immunostimulatory effect against S. mansoni infection in B. alexandrina.Keywords: Punica granatum L., Antioxidant activity, Biomphalaria alexandrina, Schistosoma mansoni, Infection rate, Gas chromatography-massspectrometry.

Diluted seawater promoted the green tide of Ulva prolifera (Chlorophyta, Ulvales)

SUMMARYUlva prolifera (Müller) J. Agardh is the main causative species of the 2008 Yellow Sea green tide incident. We investigated the influences of diluted seawater on the vegetative growth and reproductive cell formation of the alga. The thalli that were cultivated under low salinities (10‰ and 20‰) and low pH values (pH around 7.0) showed obvious and steady biomass gain, while those cultivated under high salinities (40‰) and relatively higher pH conditions (pH around 8.0) manifested significant biomass loss. The trend was, however, completely the opposite for reproductive cell formation and there were indications that enrichment, over very wide concentration ranges of both nitrogen and phosphate, could significantly promote vegetative growth. Results also indicated that relatively low salinity and low pH regimes boosted vegetative growth but were unfavorable for reproductive cell formation and vice versa. Based on these results, the possible origin and development mechanisms of the green tide event are discussed. Eutrophication in the Changjiang River estuary and adjacent sea areas, as well as extremely high freshwater inflows before, and during, the flood of 2007 – due to the full operation of large‐scale water facilities in the area – may have both played an important role in the formation and development of the green tide event.

On the Induction of Reproductive Cell Formation in the Green Alga, Enteromorpha prolifera: Relationship of Temperature and Size of Tissue Disk

On the Induction of Reproductive Cell Formation in the Green Alga, Enteromorpha prolifera: Relationship of Temperature and Size of Tissue Disk

Association between Grain Shattering Habit and Formation of Abscission Layer Controlled by Grain Shattering gene sh-2 in Rice(Oryza sativa L.).

Rice garin shattering habit is closely associated with the abscission layer formed at the base of sterile lemmas (empty glumes). In the current study, the character expression of sh-2, one of the representative shattering genes, was investigated by comparing some agronomic parameters among Norin 29, a Japanese non-shattering cultivar, and its shattering near-isogenic line SH-AJNT, as well as Dee-geo-woo-gen, a shattering indica cultivar. After observation of longitudinal sections of sterile lemmas bases, the abscission layer was not found at the spikelet differentiation stage. However, at the reproductive cell formation stage, SH-AJNT faintly formed the abscission layer. No abscission layer, on the other hand, appeared in Norin 29 throughout the stage of panicle development. The breaking strength at the base of sterile lemmas was measured to compare the threshability among materials. Until 19 days after heading, both threshability on Norin 29 and SH-AJNT exhibited similarly high values, indicating non-shattering conditions. At 21 days after heading, the garin of SH-AJNT dropped more easily than those of previou stages, while Norin 29 kept its persistent character. This difference is important for the evaluation of SH-AJNT and Norin 29, shattering and non-shattering cultivars, respectively. The progressive decline in the breaking strength of SH-AJNT was thought to be associated with the ripening of the grain.

Characterization of cDNAs Induced in Meiotic Prophase in Lily Microsporocytes

To identify and analyze genes functioning during reproductive cell formation in higher plants, cDNAs harboring the messages induced in meiotic prophase were isolated and characterized. A cDNA library constructed from microsporocytes in meiotic prophase of Lilium longiflorum was screened with a subtraction probe specific to meiotic prophase. Clones selected were classified into 18 groups by cross hybridization and partial sequencing. Northern blot analysis revealed that the transcripts corresponding to the respective cDNA groups began accumulating at the early stages of meiosis and exhibited clone-specific profiles during meiosis and the spore formation process. The amino acid sequences of the predicted gene products showed similarity with known gene products, e.g. heat shock proteins, serine proteases in Bacillus, and RAD 51 gene product in yeast. Half of the putative gene products had hydrophobic N-terminal regions, suggesting that they may function as signal peptides.

Isolation and characterization of a yeast gene that is homologous with a meiosis-specific cDNA from a plant

By using as probe a meiosis-specific cDNA clone LIM15 from the monocotyledonous plant, Lilium longiflorum, a clone containing a 2.8 kb DNA fragment was isolated from a genomic library of Saccharomyces cerevisiae. Primary structure analysis revealed that the clone includes two complete open reading frames, designated ISC2 and ISC10, capable of coding for a 36.6 kDa and a 31.6 kDa polypeptide, respectively, with the former frame being interrupted by a 92 bp intron. The predicted amino acid sequence of Isc2 was 56% identical with the putative gene product of lily cDNA clone LIM15, and showed limited sequence similarity with the yeast RAD57 gene product. Transcripts of the two genes begin accumulating 2.5 h and 7.5 h after induction of meiosis, respectively, according to a Northern hybridization analysis. Since disruption of either one of these genes had a drastic effect on the ability to form spores, ISC2 and ISC10 are expected to play significant roles in the formation of reproductive cells.

SEASONAL PATTERNS OF REPRODUCTION IN NEW YORK. POPULATIONS OF CODIUM FRAGILE (SUR.) HARIOT SUBSP. TOMENTOSOIDES (VAN GOOR) SILVA1,2

SUMMARYThe characteristics of reproduction in 2 New York populations of Codium fragile were investigated over nearly a 2‐yr period. Reproduction occurred by the exclusive formation of reproductive cells that germinated and developed, asexually. There was no evidence at any time that the reproductive cells fused and thus functioned as gametes.The relative abundance of the reproductive organs on plants in both populations exhibited a marked seasonal variation. New fronds first initiated reproductive organs during July and attained maximum values during the autumn. Formation of new reproductive organs did not occur during the winter and early spring, and those present slowly degenerated so that minimum values occurred during April–May. Reinitiation of reproductive organs on second‐year fronds started in May–June. It is proposed that a minimum temperature between 12 and 15 C is required for the initiation of reproductive organs and that temperatures below this range are inhibitory to their formation.

Crop-scientific studies on the yield-forecast of lowland rice (Preliminary report) : VI. On the relation of fruit bearing percentage to yield-forecast of rice.

Following significant relation between fruit bearing percentage and yield of rice was drawn out from the data, formerly reported on the experiments of pruning blades and roots in rice plant. (1) In this study, first of all, it was very necessary to establish an index by means of which fruited grains can be scientifically distinguished. As a result of researching the index from the stand-point of estimating rice yield, it was ascertained to be recommendable to use specific gravity of grains as the index and to take heavier grains than 1.06 of specific gravity as fruited ones. But this index holds true only in the case of dry grains (water content 12∼15%). (2) Correlation tables between fruit bearing percentage and yield, represented in persentage to the Controls respectively, are given in Fig. 1 and Fig. 2. Fruit bearing persentage can be seen to be very highly correlated with yield (r=0.99), except for the plots of No. 1∼8 in Fig. 1 and No. 1∼10 in Fig. 2. These two figures strongly suggest that in the period, at the latest, after the treatment date of No. 11 (Aug. 26, 5 days before heading), the yield of rice is mainly affected only by the fruit bearing percentage. The time of treatment on No. 11 is just the end of period when number of spikelets per ear increases, as seen in the former report (V), and there are no significant differences in number of spikelets per ears among all plots treated after it. Moreover, no significant differences are found in number of ears per plant among plots treated No.7 (Aug. 13, beginning of reproductive cell formation). Therefore; we can likely conclude that after the number of spikelets per eat and ears per plant are determined, fruit bearing percentage plays a leading role in determing the amount of rice-yield. (3) As the yield of rice is repesented by the product of its constitutional four factors, in the period after the number of ears per plant and spikelets per ear are determined it is controlled by two factors - fruit bearing percentage and weight of 1, 000 grains - which are not yet determined. In fact, however, the yield of rice, as mentioned above, is mainly affected only by fruit bearing percentage in that period. The reason why weight of 1, 000 grains has very little to do with constituting yield can be explained by its small variability. For example, Table 1 showing coefficients of variability of four factors indicates obviously that weight of 1, 000 grains is remarkably small in variability as compared with other three factors. And there are several further data supporting the stability of it. (4) From the results mentioned above, it has been made clear that one of the most important keys to solve the problem of yield-forecast in rice is to forecast the fruit bearing percentage as early as possible. Moreover, as entirely sterile grains can be recognized by the time shortly after heading, it seems to be the most urgent problem to forecast the percentage of lighter grains than 1.06 in specific gravity.

Starch Envelopes of Pyrenoids

THE pyrenoids are colourless masses of protein associated with the chromatophores in several classes of the Protophyta. They have been most studied in the Isokontae (Boubier, Bull. Herb. Boissier, 7, p. 451; 1899; Bourquin, Bot. Gaz., 64, 426; 1917), where they are embedded in the substance of the chloroplast and are covered with an envelope consisting of small starch grains which are the last to disappear under starvation conditions. The pyrenoids are generally regarded as reserve protein stores. During the formation of reproductive cells they disappear more or less completely.