Variation of the chromosome phenotype in zea,solanum and salvia

Summary InSolanum lycopersicum pachytene chromosomes the gradient in chromomere size, originating on both sides of the kinetochore, reveals the following characteristics: 1. a relatively abrupt decrease in size of the large chromomeres, 2. the gradient is related to arm length in 9 of the 12 chromosomes, 3. the gradient is particularly irregular in the short arm of the nucleolar chromosome and in the long arm is not conspicuous, 4. chromosome 6 shows an abrupt interruption in the gradient close to the kinetochore. Salvia viridis andZea mays chromosomes represent intermediate conditions between species with well defined and species without gradients. InSalvia the intermediate condition is manifested by the presence of a very large chromomere on each side of the kinetochore followed by very small chromomeres. In two chromosomes the intermediate condition is particularly apparent. In these chromosomes two chromomeres of intermediate size are present in the proximal region of the long arm. The nucleolar organizing arm has also an irregular pattern in this species.Maize has a less distinct gradient than tomato in all its chromosomes. Chromosomes 3, 4, 5 and 8 are those where the gradient is the least sharp. The nucleolar organizing arm of chromosome 6 has also an irregular pattern.In a translocation between chromosomes 5 and 6 of maize, a segment composed of very small chromomeres from the distal region of 5 which was moved to the right of the kinetochore of chromosome 6, did not change appreciably its phenotype after ten years of cultivation. During the period of cultivation a selection was made for plants where the original phenotype was preserved so that this result cannot be considered as demonstrating an absence of change in chromomere phenotype with changed position.InDrosophila andChironomus salivary gland chromosomes where chromomeres are large, and no selection has been carried out with such a purpose, the pattern and nucleic acid content of the bands is known to change when rearrangements occur within the chromosome.Supported by a grant from the Swedish Natural Science Research Council toA. Lima-De-Faria. This work was partly carried out at the Department of Botany, University of Illinois, U.S.A. during a visit to this department byA. Lima-De-Faria.P. Sarvella's collaboration in this work was done during her stay at the University of Lund.     

Pairing and transmission of a small accessory iso-chromosome in rye

Summary and conclusions A small derivative of the standard type of B chromosome in rye was definitely demonstrated to be an iso-chromosome, (i) because both arms have the same chromomere structure, (ii) because the two arms of the same chromosome frequently pair with each other and (iii) because the four arms of a bivalent at pachytene may exchange partners with each other, forming a pseudo-tetravalent.The small iso-fragment is derived from the standard fragment because the arms have a chromomere structure identical to that of the short arm of the standard fragment. This identity implies (i) that the three main chromosome regions of the short arm of the standard fragment (cf.Lima-de-Faria 1952) are also present in both arms of the small iso-fragment, (ii) that the size and distribution of the chromomeres is the same and (iii) that the cone shaped terminal part of the short arm constituted by three chromomeres may be distinguished in both the mother chromosome and its derivative, the small iso-fragment.Owing to a high degree of meiotic elimination the frequency of transmission of the small iso-fragment is low even in plants with 2 such chromosomes.     

The pachytene chromomere map of the oocyte of the Turkish hamster (Mesocricetus brandti)

A study of the chromomere maps of the sex and twenty autosomal bivalents of Turkish hamster pachytene oocytes was carried out. The average total number of chromomeres in early/mid pachytene autosomes was 280 with 91 on the p (short arm) and 189 on the q (long arm). The submetacentric X1 chromosome had 20 chromomeres and the metacentric X2 had 27. Comparisons of the number and location of oocyte chromomeres are made with the pachytene spermatocyte chromomere maps of this species.     

Chiasma maintenance and terminalization across a homoeologous bivalent segment

In maize microsporocytes Heterozygous for a chromosome 2 interchange chromosome (which carries a homoeologous Tripsacum chromosome segment substituted for the distal half of its short arm), normal synapsis usually occurs at pachytene throughout the bivalent, but crossing over is almost entirely restricted to the homologous proximal region of the arm, (where it apprently occurs frequently). At diakinesis chiasmata were very often found to be located immediately proximal to an easily observable terminal knob of the Tripscacum chromosome segment. It was concluded that chiasmata, initiated in the homologous proximal region, had been maintained while terminalizing across the homoeologous region. It was also noted that heterozygosity for a telomere (and distal region) foreign to maize does not seem to inhibit pairing effective for crossing over in the homologous proximal portion of the chromosome arm.     

Complete chromomere map of mid/late pachytene human oocytes.

A complete chromomere map of the mid/late human pachytene oocyte has been developed from ovaries of 35 fetuses at 18-22 weeks gestation. Bivalents, which were all specifically identifiable, were more extended than comparable human spermatocyte bivalents. The total number of chromomeres found was 639, exceeding both the number of human pachytene spermatocytes and the number of mitotic bands seen in metaphase somatic chromosomes. Each oocyte bivalent contained more chromomeres than the number of corresponding prometaphase chromosome bands. Similarities and differences were noted in regional comparisons of chromomere distribution between oocytes and spermatocytes.     

Localization of ribosomal DNA within the proximal X heterochromatin of Sciara coprophila (Diptera,Sciaridae)

By means of several reciprocal translocations in Sciara coprophila, each having a break-point in the proximal X heterochromatin, it has been possible in the salivary gland nucleus to bring about separation of specific regions of this heterochromatin and then, by means of in situ hybridization, to determine the relative number of ribosomal RNA cistrons in each. The three blocks of heterochromatin delineated by the translocation break-points have been designated H1, H2, and H3; H1 is the most proximal, lying immediately to the right of the X centromere, and H3 is the most distal, constituting the very end (right) of the chromosome. The distribution of ribosomal RNA cistrons is as follows: 10% are located in H1; 50% in H2; and 40% in H3. For the first time it has been possible to confirm by grain count our previous biochemical estimate of a 60% deletion of rRNA cistrons in the proximal heterochromatin of the X _W homologue. The grain count data also support the conclusion of our previously published cytological analysis, that the exchange points in the X heterochromatin are identical in translocations T29 and T32 (between H1 and H2), also in translocations T23 and T70 (between H2 and H3). The coincidence of break-points in the X heterochromatin is considered in relation to the chromomere make-up of the region. Also, the occurrence of ribosomal RNA cistrons in all three heterochromomeres is discussed in relation to the functional significance of chromomeres.     

Complete autosomal chromomere maps of human early and mid/late pachytene spermatocytes.

Specific identification of each bivalent of human spermatocytes at early and mid/late pachytene was obtained from chromomere maps developed by analyzing complete, well-spread cells from five subjects aged 31-49. The total number of chromomeres on the early autosomal bivalents was 499 and 386 at the mid/late stage. Regional analysis revealed more chromomeres at early pachytene than at mid/late, with 12 exceptions having equal numbers. Correspondence of chromomeres with mitotic prometaphase G-bands was found in all bivalents. Four chromomeres were found in region 1 of the 9q at early pachytene and two at mid/late. Differences between the map for chromosome no. 10 observed in this study and others were noted.     

Mapping of pachytene bivalents of female codling moth Cydia pomonella (Linnaeus) (Lep., Tortricidae)

Spread pachytene nuclei of codling moth Cydia pomonella (Linnaeus) (Lep., Tortricidae) females of a Syrian strain (SY) were used to investigate chromomere patterns of chromosome bivalents and determine their length. The karyotype of female codling moths consists of 28 chromosome bivalents, of which seven are clearly distinguishable using chromosome length and the number and size of the chromomeres in the pachytene stage. One autosome bivalent has two nucleolar organizing regions (NORs) that are located at the opposite ends of the chromosome and appear as distinct structural landmarks. In female codling moths, the WZ sex chromosome bivalent was easily identified in pachytene oocytes according to the heterochromatic thread of the W chromosome. This study contributed to the knowledge and identification of pachytene chromosomes of female codling moths.     

Regional control of nondisjunction of the B chromosome in maize

Control of nondisjunction in the maize B chromosome was studied using a set of B-10 translocations. The study focused on the possible effect of the proximal region of the B long arm. The experimental procedure utilized a combination of a 10^B chromosome from one translocation with a B¹⁰ from another translocation. The breakpoints of the two translocations were so located that combination of the two elements created a deletion in the proximal region of the B chromosome, but no deletion in chromosome 10. Two different types of deletions were established; one involved a portion of the euchromatic region and the other the entire heterochromatic portion comprising the distal half of the B long arm, except for the small euchromatic tip. Deletion of the heterochromatic portion did not exert any effect on nondisjunction. Deletions of different portions of the euchromatic region produce different responses. Some deletions resulted in typical B nondisjunctional activity; others resulted in the disappearance of this activity. It is concluded that a region within the euchromatic portion of the chromosome is critical for the nondisjunction of B chromosomes. Among 22 translocations with breakpoints in the euchromatic regions, three were proximal to the critical region, 16 were distal and the position of three others was not determined.     

Meiosis of trisomy 21 in the human pachytene oocyte

Association modalities of the three 21 chromosomes were studied during pachytene in three trisomy 21 fetuses whose chromosomal constitution was identified following amniocentesis. -- Three classes of images were observed: a trivalent, a trivalent presenting an important asynaptic region of the long arm, and a bivalent accompanied by a univalent. Such behaviour is analagous to that observed in all trisomic organisms. -- We have been able to establish the sequence of chromomeres, whose number varies from 9 to 14 according to the state of contraction in the 21 chromosome. Each band is thus subdivided into several sub-bands: at maximal elongation 2 sub-bands for band p11, 4 for q21 and 3 for q222. In addition, the interchromomeric clear bands q221 and q223 are also subdivided by the presence of a very small chromomere. In this way, the G-bands visible on mitotic metaphase chromosomes result from the compression together of several chromomeres whose individuality disappears as chromosomal condensation increases with progression of prophase.     

Characterization of the Na+/H+ Exchanger in the Luminal Membrane of the Distal Nephron

In the rabbit as well as the rat, a Na⁺/H⁺ exchanger is expressed in the apical membrane of both the proximal and distal tubules of the renal cortex. Whereas the isoform derived from the proximal tubule has been extensively studied, little information is available concerning the distal luminal membrane isoform. To better characterize the latter isoform, we purified rabbit proximal and distal tubules, and examined the ethylpropylamiloride (EIPA)-sensitive ²²Na uptake by the luminal membrane vesicles from the two segments. The presence of 100 μm EIPA in the membrane suspension decreased the 15 sec Na⁺ uptake to 75.70 ± 4.70% and 50.30 ± 2.23% of the control values in vesicles from proximal and distal tubules, respectively. The effect of EIPA on 35 mm Na⁺ uptake was concentration dependent, with a IC₅₀ of 700 μm and 75 μm for the proximal and distal luminal membranes. Whereas the proximal tubule membrane isoform was insensitive to cimetidine and clonidine up to a concentration of 2 mm, the 35 mm Na⁺ uptake by the distal membrane was strongly inhibited by cimetidine (IC₅₀ 700 μm) and modestly inhibited by clonidine (IC₅₀ 1.6 mm). The incubation of proximal tubule suspensions with 1 mm (Bu₂) cAMP decreased the 15-sec EIPA-sensitive Na⁺ uptake by the brush border membranes to 24.1 ± 2.38% of the control values. Unexpectedly, the same treatment of distal tubules enhanced this uptake by 46.5 ± 10.3%. Finally, incubation of tubule suspensions with 100 nm phorbol 12-myristate 13-acetate (PMA) decreased the exchanger activity to 58.6 ± 3.04% and 79.7 ± 3.21% of the control values in the proximal and distal luminal membranes, respectively. In conclusion, the high sensitivity of the distal luminal membrane exchanger to various inhibitors, and its stimulation by cAMP-dependent protein kinase A, indicate that this isoform differs from that of the proximal tubule and probably corresponds to isoform 1. Received: 6 March 1998/Revised: 6 July 1998     

DNA synthesis in the neo-X neo-Y sex determination system of Dichroplus bergi (Orthoptera: Acrididae)

DNA replication in the neo-X neo-Y sex determining system was studied by means of tritiated thymidine and autoradiography. Asynchronous replication was found in the X arm of the neo-X and the long arm of the neo-Y. In addition, striking asynchrony was also found for short isopycnotic homologous regions at the distal end of the autosmal arm of neo-X and the short arm of neo-Y to which pairing during meiosis is restricted. These short regions are asynchronous with respect to the heterochromatic segments as well as to the remaining proximal region of the autosomal euchromatic arm of neo-X. This difference in replication pattern within the same chromosome arm may be related to a differentiation between regions which are homozygous in both sexes and regions which are hemizygous in males.This work was supported by U.S. Atomic Energy Commission Contract N AT (30-1) 3517 to Prof. F. A. Saez.     

A test of homology between the B chromosome of maize and abnormal chromosome 10, involving the control of nondisjunction in B's

Summary Nondisjunction of B and B-translocation chromosomes occurs regularly in maize at the second pollen mitosis (Roman, 1947; Blackwood, 1956). The mechanism of nondisjunction was studied using the A-B interchange, TB-9b. The B⁹ chromosome of the interchange undergoes nondisjunction at the second pollen mitosis, while the 9^B chromosome does not (Roman, 1947). It was shown that the 9^B chromosome must be present in a plant for nondisjunction of the B⁹ to occur. This is consistent with the reports of Roman on TB-4a (1949) and Longley on TB-10a (1956). It was also demonstrated that the influence of the 9^B chromosome is limited to pollen grains containing it, and does not extend to all the pollen of a plant.A test of homology between the B chromosome and abnormal chromosome 10 was also made. The ability of abnormal 10 to substitute for the 9^B chromosome and induce nondisjunction of the B⁹ was tested. Nondisjunction did not occur at a detectable rate in the presence of abnormal 10, and the results failed to support Ting's proposal (1958) concerning the origin of abnormal 10.     

Development of a quantitative pachytene chromosome map in Oryza sativa by imaging methods

A higher GC content region of an Oryza sativa chromosome can be specifically visualized by double staining with propidium iodide (PI) and 4, 6-diamidino-2-phenylindole (DAPI). This procedure allows identification of chromosome 9 from the other rice chromosomes at the pachytene stage. Using rice chromosome 9 as a model, an imaging method to construct a pachytene chromosomal map was developed by quantifying the fluorescence profile (FP) of each chromomere. The pachytene map of chromosome 9 consists of twenty-two chromomeres including four chromomeres within the nucleolar organizing region (NOR) and satellite region. The pachytene map was compared with the corresponding somatic prometaphase map and the linkage map. The differences among the three maps indicate that each map depicts specific biological information, which is difficult to be substituted by the other maps.     

Multiple Mißbildungen bei einem Mädchen mit dem Karyotypus 46, XY, 17q+

Summary In a girl with multiple malformations (Pierre Robin syndrome, abortive form of dysostosis cleidocranialis, and other deformities) a spontaneous duplication-deficiency as well as the XY sex chromosomes were found. Detailed cytogenetic analysis revealed a deficiency of the distal half of the long arm of a chromosome 17. The duplication involves a region of the size of the long arm of chromosome 18. The combination of malformations as well as the autoradiographic pattern does not exclude the possibility that indeed a region of the long arm of chromosome 18 is involved.

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Wesentliche Teile der vorliegenden Arbeit werden von Herrn Dieter Bombel als Dissertation der Medizinischen Fakultät der Universität Freiburg i. Br. vorgelegt.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Meiosis in hybrids betweenLycopersicon esculentum andSolanum pennellii

Meiotic chromosome cytology was compared betweenSolanum pennellii, Lycopersicon esculentum, and the F₁ hybrid. Pachytene chromosomes are very similar in gross morphology, but several of theS. pennellii chromosomes were found to have somewhat longer chromatic regions with discrete chromomeres, and darkly staining chromomeres in the achromatic regions.Little evidence could be found for the existence of rearrangements between chromosomes of the two species. With respect to chromomere pattern, on the other hand, a number of differences were seen. Meiosis in the hybrid is strictly regular. Only size inequalities occur in certain bivalents.Considering the evidence from chromosome pairing, hybridization compatibility, hybrid fertility, and plant morphology, it is concluded that the phylogenetic relationship is much closer betweenS. pennellii andL. esculentum than it is between either one andS. lycopersicoides. Attention is called to the present unsatisfactory placement ofS. pennellii and to the need for revising the taxonomy to place it andL. esculentum in the same genus, possibly in the same subgeneric category.This research was supported in part by grant G-10704 of the National Science Foundation.     

A STUDY OF MEIOSIS IN HAPLOPAPPUS GRACILIS (COMPOSITAE)

Jackson , R. C. (U. Kansas, Lawrence.) A study of meiosis Haplopappus gracilis (Compositae). Amer. Jour. Bot. 46(7): 550–554. Illus. 1959.—A study of meiosis in the two-paired Haplopappus gracilis has shown that each pair of chromosomes is easily recognized throughout the various stages of meiosis beginning with pachytene. A comparison of mitotic and meiotic chromosomes has been made, and the data indicate that a conspicuous heteropycnotic knob on chromosome B at pachytene is the nucleolar organizer. Other recognizable chromomeres were observed, but additional study is needed before a cytological map can be drawn to show whether regions other than those described on chromosome A and B may be used as markers.     

Complete pachytene chromomere karyotypes of human spermatocyte bivalents

Summary Well-spread human pachytene spermatocyte bivalents were obtained allowing specific identification of each bivalent within its total complement according to its chromomere sequence combined with further staining of its centromeric heterochromatin. The total number of chromomeres was found to be related to the degree of bivalent contraction: 396 in condensed bivalents and 511 in decondensed bivalents. A striking correspondance between chromomeres and mitotic G-bands was observed; on account of the variability of bivalent contraction, condensed bivalents corresponded to prometaphase somatic chromosomes and decondensed bivalents to mid/late prophase chromosomes.