Median-centromeric Chromosomes Research Articles

Cytogenetical treatise of Indian representative species of Cucumis. A karyotypic approach

Karyomorphological studies have been carried out in nine species and five varieties of the genus Cucumis representing Indian gene pool. The present investigations reveal the occurrence of two somatic chromosome numbers 2n = 14, 24 in the genus. C. ritchiei and C. indicus the two new species, were found to be having somatic chromosome numbers of 2n = 24 and 2n = 20 respectively. The wild species viz. C. hystrix, C. setosus, C. prophetarum, C. dipsaceus, C. indicus have very less number of median-centromeric chromosomes, high asymmetry indices, while melon groups have intermediate number of median -centromeric chromosomes. C. sativus, C. callosus, C. ritchiei show lesser number median-cen-tromeric chromosomes and very less asymmetry indices. The importance of karyotypic variation with respect to speciation within the genus Cucumis have been discussed.

C-banding patterns in six taxa ofParis(Melanthiaceae)

C-banding patterns were analyzed in six taxa of Paris: P. polyphylla var. chinensis, P. marmorata, P. luquanensis, P. thibetica, P. polyphylla var. yunnanensis and P. polyphylla var. alba. All plants had a diploid chromosome number of 10. The basic banding consisted of three metacentric and two teloblastic chromosomes. All taxa showed interspecific variation in karyotype structure. P. thibetica had a unique C-banding pattern, having six bands on the long arm of the middle median centromeric chromosomes. P. polyphylla var. yunnanensis had mostly faint C-bands. Chromosome morphology and C-banding patterns have been used for chromosome identification and population divergence detection.

Karyological studies on eight species of Onobrychis genus in Turkey

This study used karyological techniques to determine the chromosome numbers and morphology of eight species of Onobrychis L. (O. caput-galli (L.) Lam, O. aequidentata (Sibth. & Sm.) d’ Urv, O. fallax Freyn & Sint. var. fallax, O. lasiostachya Boiss, O. viciifolia Scop., O. oxyodonta Boiss. subsp. armena (Bois. & Huet) Aktoklu, O. hypargyrea Boiss. and O. cappadocica Boiss.). The results of this study determined the chromosome numbers of O. cappadocica as 2n = 16; O. viciifolia as 2n = 28 and the other species as 2n = 14 The karyotypes of species consisted of median-centromeric (m) or submedian-centromeric (sm) chromosomes. However, O. oxyodonta Boiss. subsp. armena (Bois. & Huet) Aktoklu was found to have only the median-centromeric (m) chromosomes. According to the results of the present study, of the eight Onobrychis taxa, only O. hypargyrea has a pair of satellite chromosomes (sat-chromosome). Furthermore, this study detected karyotype asymmetry.

Characterization of chromosome complement in Tridactylina kirilowii (Turcz. ex DC.) Schultz-Bip. by aceto-orcein, CMA, DAPI and FISH

Tridactylina kirilowii (Turcz. ex DC.) Schultz-Bip., the Anthemideae Cass., Asteraceae displayed the chromosome number of 2n=18 for the first time. The chromosomes of the species at mitotic metaphase were characterized by chromosome size, centromeric position, distribution of the G-C and A-T heterochromatin-rich regions by aceto-orcein, CMA, DAPI, and FISH. The smallest chromosome at mitotic metaphase was approximately 4.1±0.5 µm, while the largest chromosome was 6.9±0.7 µm. The total length of the chromosome complement at mitotic metaphase was 97.5±7.9 µm. The chromosome complement at mitotic metaphase showed 16 median-centromeric chromosomes and two submedian-centromeric chromosomes. The CMA stained the whole chromosomes, and showed four brighter bands on the terminal positions of four chromosomes and were convenient with the four sat-chromosomes. DAPI stained the whole set of the chromosomes at mitotic metaphase, while CMA-DAPI positively, brightly stained some heterochromatin regions in the chromosomes at mitotic prometaphase Applying FISH using the digoxigenin labeled pTa71 probe of 45S rDNA to sets of the mitotic chromosomes showed four red colored signals that were located at the terminal region displayed after hybridization of the probe with four median chromosomes at mitotic metaphase.

Cytogenetical and ecological studies of some wild congeneric species in the Solanaceae distributed in upper Egypt

Cytogenetical and ecological studies in some species of the Solanaceae were made in the Mediterranean-type ecosystem in Upper Egypt. The chromosome complement of Datura innoxia (2n=24) consisted of 24 median-centromeric chromosomes; that of D. stramonium (2n=24) consisted of 22 median- and two submedian-centromeric chromosomes; that of Hyoscyamus albus (2n=68) consisted of 62 median- and six submedian-centromeric chromosomes, that of H. muticus (2n=28) consisted of 21 median- and seven submedian-centromeric chromosomes; that of Withania somnifera (2n=36; new count) consisted of 27 median- and nine submedian-centromeric chromosomes; and that of Solanum nigrum (2n=72) consists of 68 median and four submedian-centromeric chromosomes. Thirty-three reproducible polymorphic bands were resulted after four RAPD-PCR primers; those bands were used for studying the genetics similarity among the species. Average similarity coefficient was ranged from 0.05 to 0.47. RAPD bands resulted after PCR: D. innoxia and D. stramonium showed five bands each; H. albus and H. muticus showed two and one bands respectively; W. somnifera seven bands and S. nigrum showed 13 bands, different patterns were produced among congeneric species. Ionic status of hot water extract of the species revealed that Hyoscyamus species was more accumulated Na+ and Ca++, while Datura species accumulated more K+ and Mg++ and W. somnifera and S nigrum were intermediate. These strategies of ionic accumulation were in relation to the different chromosome number of species, which might help for surviving the species in desert ecosystem.

Karyomorphological studies of some species of Chrysanthemum sensu lato in Egypt

Chromosome numbers and karyotypes are presented in eight taxa in Chrysanhemum senu lato (Asteraceae). Achillea santolina, Cotula barbata and Co. cinerea had new counts for the first time. The chromosome complement of Artemisia arborescens (2n=18) consists of 14 median and four sub- median chromosomes. Achillea fragrantissima (2n=18) consists of 14 median and four sub- median chromosomes; Ach. santolina (2n=36) consists of 26 median- and ten submedian-centromeric chromosomes. Glebionis coronaria (2n=18) consists of 18 median-centromeric chromosomes; while G. coronaria var. discolor (2n= 18) has 16 median- and two submedian-centromeric chromosomes. Cotula barbata (2n=16) consists of 12 median- and four sub-median-centromeric chromosomes, while Co. cinerea (2n=18) has 14 median- and four sub-median-centromeric chromosomes. The chromosome complement of Matricaria recutita (2n=18) consists of 14 median-, two submedian- and two subterminal-centromeric chromosomes.The longest chromosome complement was Artemisia arborescens while the shortest was Cotula barbata. The length of the tetraploid chromosome complement of Ach. santolina was approximately one third shoter than the diploid Artemisia arborescens, and equal to G. coronaria.

Rapid genome reshuffling induced by allopolyploidization in F1 hybrid in Chrysanthemum remotipinnum (formerly Ajania remotipinna) and Chrysanthemum chanetii (formerly Dendranthema chanetii)

Allopolyploidization was investigated in an artificial F1 hybrid between Chrysanthemum remotipinnum (2n=18) and Chrysanthemum chanetii (2n=36). Homoeologous and non-homologous chromosomes could pair in the PMC of the hybrid that showed complex pairings and configurations at diakinesis. Physical maps of the 5S and 45S rDNA genes were generated by fluorescence in situ hybridization (FISH) for the F1 hybrid that had four signals of the 5S rDNA sites in four median-centromeric chromosomes and were different from that of C. remotipinnum, which had four signals in two median-centromeric chromosomes. The hybrid did not show any of the double signals 5S rDNA like C. remotipinnum did. FISH signals of 45S rDNA showed that the hybrid had eight signals of the 45S rDNA sites and seemed to keep the four signals of C. remotipinnum. Genomic in situ hybridization (GISH) distinguished respective parental chromosomes in the F1 hybrid chromosome complement and showed that approximately 18-yellow-colored chromosomes were hybridized with the probe of C. remotipinnum while the other 18 red-colored chromosomes that were not hybridized could be of C. chanetii. GISH detected translocations at different chromosomal sites and duplication exists in the maternal genome side.

Comparison of karyotype and rDNA-distribution in somatic chromosomes of Bowenia species (Stangeriaceae, Cycadales)

Somatic chromosomes at mitotic metaphase of Bowenia serrulata, B. spectabilis and B. sp. ‘Tinaroo’ is investigated by the standard aceto-orcein staining method and the fluorescent in situ hybridisation method (FISH) with ribosomal DNA (rDNA) probe. Bowenia serrulata, B. spectabilis and B. sp. ‘Tinaroo’ each have a chromosome number of 2n = 18. The karyotype of B. serrulata exhibits 10 median-centromeric chromosomes, while B. spectabilis and B. sp. ‘Tinaroo’ exhibit eight median-centromeric chromosomes. By using FISH, B. serrulata, B. spectabilis and B. sp. ‘Tinaroo’ show a hybridisation signal on the satellite of the short arm of two submedian-centromeric chromosomes. However, the other hybridisation signal pattern is different among B. serrulata, B. spectabilis and B. sp. ‘Tinaroo’.

Comparative karyotype analysis ofCeratozamia mexicana andMicrocycas calocoma (Zamiaceae) using fluorochrome banding (CMA/DAPI) and fluorescence in situ hybridization of ribosomal DNA

Orcein staining, differential staining with CMA and DAPI, and FISH with an rDNA probe were used to compare somatic chromosomes ofCeratozamia mexicana andMicrocycas calocoma. CMA-positive dots and hybridization signals appeared on chromosomes at early interphase and mitotic prophase, but in significantly different number in the two species. InCeratozamia mexicana, the CMA-positive and DAPI-negative bands and the hybridization signal were located at the terminal region of the long arm of three median-centromeric chromosomes, the terminal region of the short arm of two median-centromeric chromosomes and the terminal region of the long arm of two subterminal-centromeric chromosomes. InMicrocycas calocoma, they were located at the pericentric region of two median-centromeric chromosomes. These chromosome data suggested thatMicrocycas has no simple Robertsonian relationship toCeratozamia.

Comparative karyomorphology and interrelationships ofSelaginella in Japan

Karyomorphological comparisons were made of 16 native and cultivated species ofSelaginella in Japan. The somatic chromosome numbers are 2n=16 inS. boninensis; 2n=18 inS. doederleinii, S. helvetica, S. limbata, S. lutchuensis, S. nipponica, S. selaginoides, S. tama-montana, andS. uncinata; 2n=20 inS. biformis, S. involvens, S. moellendorffii, S. remotifolia, andS. tamariscina; 2n=30 inS. rossii; and 2n=32 inS. heterostachys. The interphase nuclei of all species examined are uniformly assigned to the simple chromocenter type. The metaphase karyotype of 2n=16 (x=8) is 8 m (=median centromeric chromosomes)+8(st+t)(=subterminal and terminal). The group of the species having 2n=18 (x=9) is heterogeneous karyomorphologically: The karyotype ofS. nipponica is 2n=18=6 m+12(st+t),S. tama-montana 10 m+2 sm(=submedian)+6(st+t), andS. uncinata 6 m+7 sm+5(st+t). Although the remaining five species have the common karyotype 8 m+4 sm+6(st+t), the values of mean chromosome length are variable. Another group of the specles having 2n=20 (x=10) is homogeneous, since all species have the same karyotypes 8 m+4 sm+8(st+t) and have similar chromosome size. The karyotype of 2n=30 is 12 m+6 sm+12(st+t) and is suggested to be a triploid of x=10, and 2n=32=16m+16(st+t), a tetraploid of x=8. Thus, three kinds of basic chromosome numbers, x=8, 9, 10 are present in JapaneseSelaginella examined, and their karyomorphological relationships are discussed.

Karyomorphology of the genusLycopodium sensu stricto and relationships among species

Karyomorphological comparisons were made of six species of JapaneseLycopodium sensu stricto. There were no marked differences at interphase and prophase among the six species.Lycopodium annotinum had 2n=68 and the formula of its metaphase karyotype was 18m(median centromeric chromosomes)+12sm(submedian)+12st(subterminal)+26t(terminal).Lycopodium casuarinoides had 2n=68=16m+10sm+18st+24t,L. clavatum 2n=68=22m+12sm+18st+16t, andL. obscurum 2n=68=10m+22sm+20st+16t. Each of these species, which belong to different sections, displayed several karyomorphological differences. Among themL. casuarinoides differs largely from the others in its mean chromosome length, ratio of the longest chromosome to the shortest, and frequency of m+sm chromosomes. BothLycopodium complanatum andL. nikoense, belonging to sectionComplanata, had a common karyotype 2n=46=10m+12sm+18st+6t. This section displayed a low differentiation in its karyotype. In the wholeLycopodium s.s., the ratios of m+sm in a complement varied from 38 to 50%, being higher among pteridophytes.

Karyomorphological studies onWoodwardia sensu lato of Japan

Karyomorphological comparisons were made of five species of JapaneseWoodwardia. There were no marked differences at interphase and prophase among the five species.Woodwardia japonica, W. prolifera, andW. unigemmata were diploid with 2n=68 and the formulas of their metaphase karyotypes uniformly 4m(median centromeric chromosomes)+12sm(submedian)+52(st+t)(subterminal and terminal).Woodwardia orientalis was tetraploid with 2n=136 and 8m+24sm+104(st+t), and the ratio of each chromosomal type to total complement was identical to that of three diploid species. These four species had several characteristics in common:x=34, the longest chromosome of sm, and a mean chromosome length over 3.0 μm. AlthoughWoodwardia orientalis showed some similarity toW. prolifera, it seems to be an allotetraploid which originated by chromosome doubling of a hybrid ofW. prolifera and a diploid species as yet karyomorphologically unknown.Woodwardia kempii was tetraploid with 2n=124 and 8m+24sm+92(st+t), and differed from the others in havingx=31, the longest chromosomes of t, and a mean chromosome length under 3.0 μm. This species has been classified as an independent genus,Chieniopteris, and our karyomorphological study supports this treatment.

Shortening the biennial life span of Swertia puniced by using tissue culture to obtain season-free inflorescences.

Tissue segments from stalked second-year-plants of the biennial Swertia punicea induced calli when they were cultured on the LS gelrite media containing 1μM NAA and 1μM BA, or 1μM NAA and 10μM BA, or 1μM 2, 4-D and 1μM BA, in combination. Those calli were rapidly propagated on the LS gelrite medium containing 0.5μM NAA or 2, 4-D at 25°C at a relative humidity of 65% under an illumination of 2, 000 lux for 12hr. After approximately 60 days of the callus culture in the LS gelrite medium containing 0.5μM IAA and 0.5μM BA, they began to produce numerous adventitious buds which later regenerated plantlets. Those plantlets were chromosomally rather stable clones with the stable karyotype of 26 median-centromeric chromosomes at mitotic metaphase. Large enough plantlets having several leaves of 7-8cm long and many roots were transplanted in pots in vivo and acclimated in environment at above 15°C and relative humidity above 65% for a week. After about three months at any season if cultivated at above 15°C, they usually bolted stems and produced inflorescences. Thus, this culture system shortened the biennial life-span of Swertia punicea.