Genome remodelling in three modern S. officinarumxS. spontaneum sugarcane cultivars

Abstract

This study provides evidence that nuclear and chromosome remodelling has taken place in sugarcane, a vegetative crop with a complex genome derived from interspecific hybridizations between Saccharum officinarum and S. spontaneum. Detailed knowledge on the chromosomal compositions of the three clones analysed was acquired. (1) All hybrid cultivars were found to be aneuploid, affecting both parental genomes (having chromosomes in addition to full genomes), with chromosome numbers from 2n=102-106 in My5514 and up to 2n=113-117 in C236-51. (2) Comparative in situ hybridization showed that about 16% of these chromosomes are inherited from S. spontaneum and less than 5% are recombinant or translocated chromosomes containing sequences of both S. officinarum and S. spontaneum. (3) Differences between the observed DNA contents (estimated by flow cytometry) and those expected from the number of chromosomes, allowed the introgression of additional S. spontaneum or S. officinarum DNA pieces into the B42231 and C236-51 cultivars to be estimated. (4) Size heterogeneity between S. officinarum homologous chromosomes carrying the 18S-5.8S-25S and 5S ribosomal genes (identified by FISH with pTa71 and pTa794, respectively) confirms remodelling occurred by chromosomal interchange events, at least in these homologous chromosomes. (5) Simultaneous visualization of nucleoli and NORs showed that all 18S-5.8S-25S loci were potentially functional in the three clones, independent of their origin and size.

Prolamin storage proteins and alloploidy in wild populations of the small grass Brachypodium distachyon (L.) P. Beauv.

“…Preparations and probe denaturation, in situ hybridization, post-hybridization washing, and detection were all performed according to Cuadrado et al (2004).…”

Meiotic analysis and FISH with rDNA and rice BAC probes of the Thai KPS 01-01-25 sugarcane cultivar

“…Descendants obtained from S. officinarum (2n = 80) 9 S. spontaneum (2n = 40-2n = 128) crosses were expected to have chromosome numbers between 100 and 144, but never were more than 130 chromosomes observed, probably due to low vigor and quality of the sugarcane at such higher chromosome numbers (Roach 1972). Studies of D 'Hont et al (1996'Hont et al ( , 1998'Hont et al ( , 2008, D'Hont and Glaszmann (2001), Piperidis and D'Hont (2001) and Cuadrado et al (2004) suggest that 70-80 % of the modern sugarcane genome originated from S. officinarum and 20-30 % from S. spontaneum, of which about 10 % is composed of homeologous recombinant chromosomes. If we assume that such a genomic composition holds true for the KPS 01-01-25 cultivar, then on average 83 chromosomes are from S. officinarum (x = 10) and so represent about eight genomes, and 28 chromosomes are from S. spontaneum (x = 8) and recombinant chromosomes, and so represent 3-4 genomes.…”

“…FISH using the 5S rDNA probe showed ten signals in a cell complement, of which five are small. Based on the Chromosomes Thai sugarcane 313 110 chromosomes of the sugarcane cultivar and the number of one rDNA per monohaploid genome (Jenkin et al 1995;D'Hont et al 1998;Cuadrado et al 2004) we estimated the number of genomes in this cultivar at 11-12, of which 8-9 genomes are from S. officinarum and 3 from S. spontaneum or recombinant chromosomes. So in fact, there is a slight discrepancy between the observed rDNA sites and the estimate numbers of genomes.…”

“…Cytogenetic studies of sugarcane and related species revealed that the basic chromosome number for S. spontaneum is x = 8, whereas S. officinarum and S. robustum have x = 10 (Ha et al 1999;Piperidis and D'Hont 2001;D'Hont 2005). Total genome sizes of modern cultivars are about 10 Gb and can contain up to 130 chromosomes, of which 80-90 % of the chromosomes originate from S. officinarum, 10-20 % from S. spontaneum and the rest from interspecific recombinations (D'Hont et al 1996;D'Hont and Glaszmann 2001;Piperidis and D'Hont 2001;Cuadrado et al 2004). Detailed knowledge on the complex polyploid genome compositions of these hybrids requires extensive genetic, genomic and cytogenetic studies.…”

“…For chromosome identification and karyotype analyses FISH with the 5S and 45S rDNA probes was used on metaphase and pachytene complements and, where possible, was supplemented with FISH using species-specific repeats. Such information is most useful for comparing chromosome sets between related (polyploid) species (Jenkin et al 1995;D'Hont et al 1998;Cuadrado et al 2004). FISH technology also allows detection of single and low copy sequences on the chromosomes.…”