title: Chromosomal localization of 45S rDNA, sex-specific C values, and heterochromatin distribution in Coccinia grandis (L.) Voigt.
abstract: Coccinia grandis is a widely distributed dioecious cucurbit in India, with heteromorphic sex chromosomes and X-Y sex determination mode. The present study aids in the cytogenetic characterization of four native populations of this plant employing distribution patterns of 45S rDNA on chromosomes and guanine-cytosine (GC)-rich heterochromatin in the genome coupled with flow cytometric determination of genome sizes. Existence of four nucleolar chromosomes could be confirmed by the presence of four telomeric 45S rDNA signals in both male and female plants. All four 45S rDNA sites are rich in heterochromatin evident from the co-localization of telomeric chromomycin A (CMA)(+ve) signals. The size of 45S rDNA signal was found to differ between the homologues of one nucleolar chromosome pair. The distribution of heterochromatin is found to differ among the male and female populations. The average GC-rich heterochromatin content of male and female populations is 23.27 and 29.86 %, respectively. Moreover, the male plants have a genome size of 0.92 pg/2C while the female plants have a size of 0.73 pg/2C, reflecting a huge genomic divergence between the genders. The great variation in genome size is owing to the presence of Y chromosome in the male populations, playing a multifaceted role in sexual divergence in C. grandis.
authors: Center of Advanced Study, Department of Botany, University of Calcutta 35, Ballygunge Circular Road, Kolkata, West Bengal, 700019, India. biplabkumar_bhowmick@yahoo.com.
authors: Biplab Kumar
authors: BK
authors: Bhowmick
authors: Faculty of Agriculture, Kagoshima University, 1-21-24, Korimoto, Kagoshima, 890-0065, Japan. yamasa@agri.kagoshima-u.ac.jp.
authors: Masashi
authors: M
authors: Yamamoto
authors: Center of Advanced Study, Department of Botany, University of Calcutta 35, Ballygunge Circular Road, Kolkata, West Bengal, 700019, India. sumitajha.cu@gmail.com.
authors: Sumita
authors: S
authors: Jha
mesh_terms: D001483:Base Sequence; D032461:Chromosomes, Plant / Q000235:genetics*; D019662:Cucurbitaceae / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D005434:Flow Cytometry; D059646:Genome Size; D018745:Genome, Plant; D006570:Heterochromatin / Q000378:metabolism*; D007621:Karyotyping; D008677:Metaphase / Q000235:genetics
chemical_list: D018744:DNA, Plant; D004275:DNA, Ribosomal; D006570:Heterochromatin
keywords: 45S rDNA; CMA; Coccinia grandis; FISH; Flow cytometry; Genome size