Disproportionate numbers of rDNA loci in diploid and polyploid testis nuclei of gerris najas detected by fluorescence in situ hybridization |
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| Authors: | T A Becker W Nagl |
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| Institution: | 1. Centro de Estudios e Investigaciones en Biodiversidad y Biotecnología (CIBUQ), Colombia;2. Instituto de Ecología A.C. Centro Regional del Bajío, Apdo. Pátzcuaro, Michoacán Postal 61600, Mexico;3. Instituto de Biotecnología y Agroindustria (IBA), Grupo de Investigación en Alimentos Frutales, Facultad de Ingeniería y Arquitectura, Departamento de Ingeniería Química, Universidad Nacional de Colombia Sede-Manizales, Colombia;4. Programa Interdisciplinario de Estudios en Plantas Vasculares. Departamento de Ciencias Básicas, INEDES-CONICET, Universidad Nacional de Luján-Ruta Nac.5 y Avenida Constitución (6700) Luján, Buenos Aires, Argentina;1. Department of Horticulture, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, 46000, Pakistan;2. Plant Systematics and Evolution Laboratory, Department of Plant Biotechnology, Atta ur Rahman School of Applied Biosciences (ASAB), National University of Sciences and Technology (NUST), Islamabad, 44000, Pakistan;3. Department of Plant Breeding and Genetics, Pir Mehr Ali Shah Arid Agriculture University Rawalpindi, 46000, Pakistan;4. National Institute for Genomics and Advanced Biotechnology, National Agriculture Research Center, Islamabad, 44000, Pakistan;5. Food and Biotechnology Research Centre, Pakistan Council of Scientific and Industrial Research (PCSIR) Laboratories Complex, Ferozepur Road Lahore, 54600, Pakistan;6. Soil and Water Conservation Research Institute, Chakwal, 48800, Pakistan;7. Department of Plant Sciences, College of Agricultural and Environmental Sciences, University of California, Davis, CA, 95616, USA |
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| Abstract: | The replication state of rDNA in testes nuclei undergoing polyploidization by classical-type endomitosis was investigated in Gerris najas (Heteroptera) by means of fluorescence in situ hybridization. The number of just one rDNA locus per haploid genome was determined by in situ hybridization on meiotic nuclei. Additionally, DNA measurements of spermatids and testes nuclei were performed. Although regular duplication levels of nuclear DNA were found within the limits of the accuracy of the method, these did evidently not apply to the ribosomal genes. The comparison of the number of rDNA signals with the DNA content of 106 testis nuclei revealed drastic variations of the number of rDNA loci between individual nuclei with similar DNA content. Polyploid nuclei of the testis epithelium showed too low numbers of rDNA loci in relation to those expected from the levels of ploidy, while cyst cell nuclei displayed increased numbers of rDNA loci. The results indicate that the ribosomal genes are either underreplicated, or in part eliminated, during the endomitotic cycles of epithelium cell nuclei, but amplified in the cyst cell nuclei, probably already at their diploid stage. |
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| Keywords: | ribosomal genes underreplication somatic elimination amplification endomitosis |
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