Analysis of basic proteins during spermatogenesis in the cricket, Acheta domestica

Triplex configuration in the nick-free DNAs that constitute the chromosomal scaffolds in grasshopper spermatids

After applying proper deoxyribonucleic acid (DNA) probes, fluorescence in situ hybridization (FISH) showed that the 8/9 centromeres-one per chromatid of the male haploid complement (X0) of Pyrgomorpha conica grasshopper-colocalized at the spermatid blunt end, where the spermatozoa flagellum inserts. A bundle of aligned 4',6-diamidino-2-phenylindole-positive chromatid scaffolds, which formed the central spermatid core, was observed after DNA breakage detection followed by FISH. Modular nature of scaffold DNA was occasionally evident. The technique also showed that in the early spermatid, the chromatid scaffolds lacked any DNA nick, whereas abundant breaks accumulated in the surrounding loops. Moreover, immunodetection showed that scaffold DNA participated in the formation of triplex DNA, while this configuration was absent from the loops. During spermatid maturation, triplex DNA disappeared from the scaffold in parallel with loop retraction, while protamines replace histones. Thus, the presence of triplex DNA in the chromatid scaffold correlates with the anchoring of expanded DNA loops to it. After loop retraction, the scaffolds of all chromatids coiled as a single unit in the spermatid head. This cooperative coiling produced enlargement and tilting of the distal telomeric signals, which were distributed along the spermatid head according to the length of each chromosome. We propose that specific DNA sequences dispersed throughout the whole chromatid fold forward and backward coaxially to chromatid length, forming individual scaffold modules whose linear assembly accounts for the minimum length of each individual chromatid. Finally, the core of the grasshopper male spermatid should be considered as a single chromosome in which the DNA scaffolds of the whole set of the nonhomologous chromosomes of the haploid complement are interconnected. This pattern of chromatin organization applies probably to other elongated spermatids.

Packaging of DNA in cricket sperm. A compact mode of DNA packaging

The packaging of DNA in the sperm of the house cricket (Gryllus bimaculatus) was investigated by microscopical and diffraction methods. The principle of DNA packaging in the cricket sperm is parallel bundling. This is in contrast with that in somatic cells, which assumes successive supercoiling. About 240 threads of DNA are bundled into one 300 A fiber, and then more than 200 fibers (300 A) are packed in a parallel manner in one nucleus. Therefore, DNA is oriented so that its helix axis is parallel with the long axis of the nucleus. This simple packaging of DNA is maintained by a newly discovered protein, 17 K protein; no histones were found. The packaging ratio (the ratio of the volume of DNA to that of the suprastructure) of the chromatin is about 1 and shows an effectiveness much higher than that of the nucleosome solenoid structure. The mode of packaging DNA in cricket sperm is different from the nucleosome structure, and is a quite new type of packaging.

Lability to acid hydrolysis in some different DNA-protein complexes of spermatozoa

The Feulgen hydrolysis kinetics was investigated in spermatozoa with different composition in DNA-protein complexes. The species used were: Bos taurus (arginine rich nuclear protein also containing cystine residues), Pichroplus bergi, Triatoma infestans (arginine-rich nuclear protein), Lytechinus variegatus and Apis mellifera (lysine-rich nuclear protein). The spermatozoa were subjected to Feulgen's reaction, after varying the fixative type and the hydrolysis times. Feulgen-DNA values were obtained with an automatic scanning cytophotometric procedure. Differences were demonstrated in the hydrolysis kinetics as a function of differences in composition of the DNA-protein complexes being present in the spermatozoon chromatin. Differences in the profiles of Feulgen hydrolysis curves, having for basis the fixation, were rather clear for bull, grasshopper, and blood-sucking insect spermatozoa than for the sea-urchin and bee spermatozoa. The different hydrolysis kinetics of chromatin of blood-sucking insect spermatozoa compared to that of grasshopper, sea-urchin, and bee sperm cells suggests that, although the first 2 materials contain an arginine-rich "germinative" protein and the latter 2 ones contain a lysine-rich protein, these differ to each other. The DNA depurination was obtained more quickly for T. infestans (20 min) and P. bergi (10 min) spermatozoa when they were fixed in the ethanol-acetic acid (EA) mixture. Morphologically anomalous bull spermatozoa fixed in the EA mixture presented a quicker depurination (30 min) as compared to the normal cells (1 h). The fast lability to acid hydrolysis in the abnormal cells is certainly due to anomalies in their basic nuclear "germinative" protein. In the formalin fixed materials the maximal depurination was obtained earlier in bull spermatozoa (30 min) followed by sperm cells of P. bergi, T. infestans, L. variegatus (all of them one-hour hydrolysis) and finally Apis mellifera (2 h hydrolysis). The presence of secondary peaks at the descending branch of the hydrolysis curves of grasshopper and sea-urchin spermatozoa, indicates for these, more than 1 kind of apurinic-acid protein complexes. The spermatozoa bearing arginine-and/or cystine-rich nuclear protein contain a more easily soluble apurinic acid protein complex. Due to the differences in hydrolysis kinetics of chromatin in spermatozoa containing different nuclear "germinative" proteins, this cellular type does not appear indicated as a haploid control for evaluation of Feulgen-DNA contents of diploid and polyploid somatic cells.

Organization of chromatin during spermiogenesis: beaded fibers, partly beaded fibers, and loss of nucleosomal structure

The aggregation of chromatin during spermiogenesis in the house cricket and many other animals is an orderly process involving the formation of a series of long, thick, well defined structures. The differentiation of chromatin preliminary to the development of such unusual structures is given attention here. Examination of nuclei after lysis and spreading indicated that fibers with closely spaced nucleosomes, like the fibers of somatic chromatin, make up the chromatin in all stages of early spermiogenesis and most of middle spermiogenesis. The thick structures of late spermatids cannot be formed by aggregation of fibers of this somatic type, however; just before thick structures form, chromatin fibers lose the nucleosomal structure. During the process, fibers with nucleosomes spaced at irregular intervals and with long stretches of smooth thin fiber are found, as if nucleosomes at one site on a fiber are broken down independently of those at adjacent sites. Since prior studies of cricket proteins have indicated that somatic histones persist during the stages when nucleosome structure disappears, the observations imply that the histones which are organized in nucleosomes during early stages must become incorporated into different kinds of nucleoprotein complexes during succeeding stages of spermiogenesis.

Cytophotometric analysis of basic nuclear proteins during gametogenesis in the free-living nematode Panagrellus silusiae

The cytochemical staining characteristics of basic nuclear proteins during gametogenesis in both sexes of the free-living nematode Panagrellus silusiae were monitored by absorption microspectrophotometry. During spermatogenesis, the levels of both of the nuclear-bound Sakaguchi and 1-fluoro-2, 4-dinitrobenzene (FDNB) reagents per Feulgen-DNA content increase prior to meiosis and subsequently drop off during spermiogenesis. During oogenesis, the amount of Sakaguchi-protein to DNA ratio rises slightly whereas the FDNB-protein to DNA ratio undergoes a meagre decline. Since the oocyte of Panagrellus accumulates DNA in excess of a 4C DNA equivalent, the relative constancy of the ratio of basic nuclear protein content to DNA amount during oogenesis signifies that these proteins are being continously produced during oocyte maturation. After treatment with alkaline fast green (pH 8.1) the cytoplasmic and nuclear regions of the gonocytes of both sexes yield such an intense reaction that microspectrophotometric measurements could not be taken. The basis of the cytoplasmic staining reaction to the fast green (pH 8.1) dye was not determined. The rapid, highly deterministic programme of embryogenesis in Panagrellus may require a substantial stockpiling of basic nuclear proteins during oogenesis.

An analysis of MP gene affected morphogenesis in Tetrahymena pyriformis, syngen 1, (Species 1) ciliates

The recessive mp gene in syngen 1 (Species 1) of Tetrahymena pyriformis results in a characteristic set of abnormalities of the adoral membranelles, commonly including some extra membranellar segments (Kaczanowski, '75). The abnormal pattern is produced in about 10% of dividing cells, compared to 80% of cells undergoing oral replacement. Thus the percentage of abnormal cells increases during prolonged stationary phase. Abnormal oral replacement arises primarily for a separation of two kinetosomal fields: the field of kinety no. 1 (the K-1 field), and the anterior field originating from the displaced undulating membrane. Both sites of proliferation appear also during wild type morphogenesis, but they fuse early to form one integrated field (Frankel, '69). The prolonged separation of the subfields in mp/mp cells results in a separate assembly of adoral membranelles; however, the independently developing membranelles of the two subfields are united later to produce a single oral apparatus. A single gene-dependent factor apparently alters some property of the cortical layer, which in turn is responsible for a reduced integrity of the oral replacement primordium.