Molecular cytogenetic characterization and comparison of the two cultivated Canavalia species (Fabaceae)

Abstract

The two cultivated Canavalia (Adanson, 1763) species, Canavalia gladiata (N. J. von Jacquin, 1788) A. P. de Candolle, 1825 and Canavalia ensiformis (Linnaeus, 1753) A. P. de Candolle, 1825 are closely related based on morphological and molecular phylogenetic data. However, the similarities and differences in genome organization between them have not been evaluated at molecular cytogenetic level. Here, detailed karyotypes of both species were constructed using combined PI and DAPI (CPD) staining, rDNA-FISH and self-genomic in situ hybridization (sGISH). For further comparison, comparative genomic in situ hybridization (cGISH) and sequence analysis of 5S rDNA were applied. Their chromosomes were accurately identified by sGISH and rDNA-FISH signals. Both species had the karyotype formula 2n = 22 = 18m + 4m-SAT, but the karyotype of C. ensiformis was shorter and more asymmetric than that of C. gladiata. They displayed similar CPD bands at all 45S rDNA sites and centromeres. C. gladiata had ten centromeric 5S rDNA loci and two SC (secondary constriction)-associated 45S rDNA loci. C. ensiformis had nine centromeric and one interstitial 5S loci, two SC-associated and one proximal 45S loci. Their sGISH signal patterns displayed both basic similarities and distinct differences. Reciprocal cGISH generated prominent signals in all pericentromeric regions and 45S sites. There was lower level of sequence identity of the non-transcribed spacer between their 5S rDNA repeats. These data confirmed the evolutionary closeness between C. gladiata and C. ensiformis and demonstrated obvious differentiation between their genomes, and supported the opinion that C. ensiformis is more advanced in evolution than C. gladiata.

The epigenetic regulation of centromeres and telomeres in plants and animals

“…Centromeric DNA sequences are evolving relatively fast ( Melters et al 2013 ), which seems surprising considering the conservative function of the centromere ( Henikoff et al 2001 , Rosin and Mellone 2017 ). Large differences in centromere sequences among wild Oryza species (Linnaeus, 1753) ( Lee et al 2005 ), cultivated Canavalia (Adanson, 1763) species ( She et al 2017 ), between related species of Solanum tuberosum (Linnaeus, 1753) and S. verrucosum (Schlechtendal, 1839) ( Zhang et al 2014 ), or within one species of Pisum sativum (Linnaeus, 1753) ( Macas et al 2007 ), can serve as examples. Hence, it is presumed that centromeres are not genetically determined by the occurrence of a specific DNA sequence, but they are rather epigenetically defined by characteristic modifications ( Simon et al 2015 ).…”

Comparative molecular cytogenetic characterization of five wild Vigna species (Fabaceae)

“… Moscone et al 1999 ; Hasterok et al 2001 ; Chung et al 2008 ; Hamon et al 2009 ; Robledo et al 2009 ; Wolny and Hasterok 2009 ; She et al 2015 ; Li et al 2016 ; Maragheh et al 2019 ). Fluorochrome banding techniques using double fluorescent dyes such as CMA3 (chromomycin A3) / DAPI (4’,6-diamidino-2-phenylindole) staining, and PI (propidium iodide)/ DAPI staining (called CPD staining) was used to localize the chromosome regions that are rich in GC and AT base pairs simultaneously, providing effective identifying markers for chromosomes, and revealing characteristic heterochromatin distribution along chromosomes ( She et al 2006 ; de Moraes et al 2007 ; de A Bortoleti et al 2012 ; She and Jiang 2015 ; She et al 2015 , 2017 ; Tang et al 2019 ).…”

“…Detailed karyotypes can be constructed using the dataset of rDNA - FISH signals, fluorochrome bands and chromosome measurements, which reveals the genome organization of a plant species at chromosome level and is valuable in investigating the evolutionary relationships between related species (e.g. Moscone et al 1999 ; de Moraes et al 2007 ; Hamon et al 2009 ; Robledo et al 2009 ; Mondin and Aguiar-Perecin 2011 ; She and Jiang 2015 ; She et al 2015 , 2017 ; Zhang et al 2015 ; Amosova et al 2017 ; Tang et al 2019 ) and helpful to integrate the genetic and physical maps of a plant species ( Fuchs et al 1998 ; Fonsêca et al 2010 ). Comparative genomic in situ hybridization ( cGISH ) is a modification of the GISH technology in which the labelled total genomic DNA of one species is hybridized to the chromosomes of another species without the competitive DNA.…”

Low cytomolecular diversification in the genus Stylosanthes Sw. (Papilionoideae, Leguminosae)

“…In the genus Crotolaria, different heterochromatin types were observed, suggesting the occurrence of replacement of repetitive DNA families during the genus diversification (Mondin et al, 2007;Mondin and Aguiar-Perencin, 2011;Morales et al, 2011). In Astragalus, Stylosanthes cytomolecular traits 7 it was reported variation in number, intensity, and position of CMA bands along the chromosomes, likewise 5S rDNA sites (Baziz et al, 2014), while cultivated species of Canavalia showed variations in the rDNA positions (She et al, 2017). In Lotus japonicus (Regel) K. Larsen and L. filicaulis Durieu, for which three 35S loci have been identified, initially no polymorphism of this type was observed (Pedrosa et al, 2002).…”