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Phaseolus polytene chromosomes

Nagl, W., Dept. of Biology, University of Kaiserslautern, Aug 1996

Polytene chromosomes

Polytene chromosomes represent a special structural organization of polyploid interphase nuclei, which originate by repeated endoreduplication cycles. A prerequisite for polytenization is the absence of any kind of mitotic chromosome condensation during cell growth. Independent of their species-specific structure, polytene chromosomes are characteristic of terminally differentiated cells of high and specialized synthetic activity. Although polyteny is best known from larval salivary glands and other tissues in dipters, essentially the same nuclear organization can be found in many different taxa throughout the animal and plant kingdoms (for reviews and further information see below).

Although plant polytene chromosomes correspond to those of dipters in respect to their development, genetic organization and function, their morphology normally is somewhat different. Their banding pattern is poorly developed, their degree of condensation varies considerably, and they are - in most cases - not somatically paired. Their general appearance differs between species, what can be primarily understood on the basis of different species-specific structures of the diploid interphase nuclei (Nagl et al., 1983; Nagl, in press). For reviews and further information see below.

Polytene chromosomes in Phaseolus

In Phaseolus coccineus and P.vulgaris (and sometimes in different other species), polyteny occurs in the basal giant cells of the embryo-suspensor (review: Nagl, 1974). The suspensor, a short-lived differentiation of the embryo proper, deals both as transfer system for nutrients and as an organ of high sythetic activity, including phytohoromes (Nagl, 1985). It develops early in embryogenesis and undergoes autolysis before the seed ripens.

In allmost all cells, the polytene chromosomes display a granular euchromatic structure with some fuzzy bands, and distinct heterochromatic regions. A clear banding pattern is found very rarely. It particularly occurs under conditions of inhibiting transcription. Fig. 1 shows a banded polytene chromosome of P.vulgaris in comparison with mitotic chromosomes. Except the nucleolus-organizing chromosomes, the Phaseolus mitotic and polytenic chromosomes are hardly distinguished.

Fig. 1. a) An in part banded polytene chromosome of Phaseolus vulgaris cv. Hilds Marona. The plants were chilled bevore harvesting to respectively 12°C and 8°C at a day/night regimen of 13/11 hrs for two weeks (Nagl, 1969). Fixed with ethanol/acetic acid (3:1), phase contrast, 1500 x. b) Mitotic chromosomes from a root tip after colchicine treatment. Feulgen, 1500 x. Foto kindly provided by Prof. W. Nagl 1996.

Therefore, various additional methods, such as fluorescence in situ hybridization, are now used to establish a polytene karyotype (Nenno et al.,1993, 1994). Fig. 2 shows the idiogram of the preliminary polytene karyotype and the localization of the ribosomal RNA genes (rDNA) and phaseolin genes used as molecular markers.

Fig. 2 Idiogram of the preliminary polytene karyotype of Phaseolus coccineus. Hybridization sites of DNA probes for the 18S-5.8S-25S ribosomal RNA genes (R) and phaseolin genes (P) used as molecular markers. Foto kindly provided by Prof. W. Nagl 1996.

References

• Nagl, W.: Banded polytene chromosomes in the legume Phaseolus vulgaris. Nature 221, 70-71 (1969).
• Nagl, W.: The Phaseolus suspensor and ist polytene chromosomes. Z.Pflanzenphysiol. 73, 1-44 (1974).
• Nagl, W., Jeanjour, M., Kling, H., Kühner, S., Michels, I., Müller, T., Stein, B.: Genome and chromatin organization in higher plants. Biol.Zentr.bl. 102, 129-148 (1983).
• Nagl, W.: Chromosomes in differentiation. In: Advances in Chromosome and Cell Genetics (Sharma, A.K., Sharma, A., Eds.), 135-172. Oxford & IBH Publ.Co., New Delhi (1985).
• Nenno, M., Schumann, K., Nagl, W.: Mapping phaseolin genes to polytene chromosomes by fluorescence in situ hybridization (FISH). Annu. Rep. Bean Improv. Coop. (BIC) 36, 3-4 (1993).
• Nenno, M., Schumann, K., Nagl, W.: Detection of rRNA and phaseolin genes on polytene chromosomes of Phaseolus coccineus by fluorescence in situ hybridization after pepsin treatment. Genome 37, 1018-1021 (1994).
• Nenno M., Zink D., Nagl W.: Localization of different microsatellites and a minisatellite-like sequence on polytene chromosomes of Phaseolus coccineus. Annu. Rep. Bean Improv. Coop. (BIC) 39, 245-246 (1996)
• Nagl W.: Polytene Chromosomes. In: Fukui K., Nakayama S. (Eds.). Plant Chromosomes: Laboratory Methods. Boca Raton: CRC Press. 51-83 (1996).

Additional references

• Avanzi, S., Durante, M., Cionini, P.G., D´Amato, F.: Cytological localization of ribosomal cistrons in polytene chromosomes of Phaseolus coccineus. Chromosoma 39, 191-203 (1972).
• Durante, M., Cremonini, R., Tagliasacchi, A.M., Forino, L.M.C., Cionini, P.G.: Characterization and chromosomal localization of fast renaturing and satellite DNA sequences in Phaseolus coccineus. Protoplasma 137, 100-108 (1987).
• Forino, L.M., Tagliasacchi, A.M., Avanzi, S.: Different structure of polytene chromosomes of Phaseolus coccineus suspensors during early embryogenesis. Protoplasma 101, 231-246 (1979).
• Frediani, M., Forino, K.M.C., Tagliasacchi, A.M., Cionini, P.G., Durante, M., Avanzi, S.: Functional heterogeneity, during early embryogenesis, of Phaseolus coccineus ribosomal cistrons in polytene chromosomes of embryo suspensor. Protoplasma 132, 51-57 (1986).
• Frediani, M., Cremonini, R., Salvi, G., Caprari, C., Desiderio, A., D´Ovidio, R., Cervone, F., De Lorenzo, G.: Cytological localization of the PGIP genes in the embryo suspensor cells of Phaseolus vulgaris L. Theor.Appl.Genet. 87, 369-373 (1993).
• Tagliasacchi, A.M., Forino, L.M.C., Cionini, P.G., Cavallini, A., Durante, M., Cremonini, R., Avanzi, S.: Different structure of polytene chromosomes of Phaseolus coccineus suspensors during early embryogenesis. 3. Chromosome pair VI. Protoplasma 122, 98-107 (1984).
• Tagliasacchi, A.M., Forino, L.M.C., Frediani, M., Cremonini, R., Tucci, G., Maggini, F., Avanzi, S.: Ribosomal RNA genes in Phaseolus coccineus. 2. Differential distribution of ribosomal cistrons and cytological localization of various sized replication units in polytene chromosomes of embryo suspensor. Cytobios 75, 137-147 (1993).

Reviews and further information

General

• Nagl, W.: Endopolyploidy and Polyteny in Differentiation and Evolution. North-Holland/Elsevier Publ., Amsterdam, The Netherlands (1978).
• Sorsa V.: Polytene Chromosomes in Genetic Research. Ellis Horwood Limited, Chichester, England (1988).
• Nagl, W.: Cell growth and nuclear DNA increase by endoreduplication and differential DNA replication. In: Cell Growth (Nicolini, C., Ed.), 619-651. Plenum Press, New York-London (1982).
• Nagl, W.: Cdc2-kinases, cyclins, and the switch from proliferation to polyploidization. Protoplasma 188, 143-150 (1995).
• Vázquez Nin, G.H., Echeverria, O.M.: The polytene nucleus in morphological, cytochemical, and functional studies of messenger RNA transcription, processing, and transportation. Eur. J. Histochem. 40, 7-16 (1996).
• Zhimulev, I.F.: Polytene Chromosomes. Morphology and Structure. Russ. Acad. Nauk, Novosibirsk, Russia (1992) - in Russian.
• Zhimolev I. F.: Morphology and structure of polytene chromosomes. In: Hall, J. C., Dunlap, J. C. Advances in Genetics, Vol 34. San Diego, USA, Academic Press, Series: Advances in Genetics Incorporating Molecular Genetic Medicine. (1996).

Protista

• Ammermann, D., Steinbrück, G., von Berger, L., Hennig, W.: The development of the macronucleus in the ciliated protozoan Stylonychia mytilus. Chromosoma 45, 401-429 (1974).
• Prescott, D.M., Murti, K.G., Bostock, C.J.: The genetic apparatus of Stylonychia sp. Nature 242, 576-600 (1973).

Collembola

• Cassagnau, P.: Les chromosomes polytènes de Neanura monticola Cassagnau (Collemboles). I. Polymorphisme écologique du chromosome X. Chromosoma 46, 343-363 (1974).
• Deharveng, L., Lee, B.-H.: Polytene chromosomal variability of Bilobella aurantiaca (Collembola) from Sainte Baume population (France). Caryologia 37, 51-67 (1984).

Insecta

• Beermann, W., Ed.: Developmental Studies on Giant Chromosomes. Springer, Berlin-Heidelberg-New York (1972).
• Kress, H.: Polytene chromosomes: a general model for the eucaryotic interphase state. Int.J.Insect Morphol.Embryol. 25, 63-91 (1996).
• Pardue, M.L.: Looking at polytene chromosomes. Meth.Cell Biol. (Acad.Press) 44, 333-351 (1994).

Mammalia

• Zybina, E.V., Zybina, T.G.: Polytene chromosomes in mammalian cells. Int.Rev. Cytol. 165, 53-119 (1996).

Angiospermata

• Nagl, W.: Temperature-dependent functional structures in the polytene chromosomes of Phaseolus, with special reference to the nucleolus organizers. J.Cell Sci. 6, 87-107 (1970).
• Nagl, W.: Polytene chromosomes of plants. Int.Rev.Cytol. 73, 21- (1981).
• Nagl W.: Polytene Chromosomes. In: Fukui K., Nakayama S. (Eds.). Plant Chromosomes: Laboratory Methods. Boca Raton: CRC Press. 51-83 (1996).