Dataset Information

Instability of Alien Chromosome Introgressions in Wheat Associated with Improper Positioning in the Nucleus.

ABSTRACT: Alien introgressions introduce beneficial alleles into existing crops and hence, are widely used in plant breeding. Generally, introgressed alien chromosomes show reduced meiotic pairing relative to the host genome, and may be eliminated over generations. Reduced pairing appears to result from a failure of some telomeres of alien chromosomes to incorporate into the leptotene bouquet at the onset of meiosis, thereby preventing chiasmate pairing. In this study, we analysed somatic nuclei of rye introgressions in wheat using 3D-FISH and found that while introgressed rye chromosomes or chromosome arms occupied discrete positions in the Rabl's orientation similar to chromosomes of the wheat host, their telomeres frequently occupied positions away from the nuclear periphery. The frequencies of such abnormal telomere positioning were similar to the frequencies of out-of-bouquet telomere positioning at leptotene, and of pairing failure at metaphase I. This study indicates that improper positioning of alien chromosomes that leads to reduced pairing is not a strictly meiotic event but rather a consequence of a more systemic problem. Improper positioning in the nuclei probably impacts the ability of introgressed chromosomes to migrate into the telomere bouquet at the onset of meiosis, preventing synapsis and chiasma establishment, and leading to their gradual elimination over generations.

SUBMITTER: Pernickova K

PROVIDER: S-EPMC6472020 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Instability of Alien Chromosome Introgressions in Wheat Associated with Improper Positioning in the Nucleus.

Perničková Kateřina K Koláčková Veronika V Lukaszewski Adam J AJ Fan Chaolan C Vrána Jan J Duchoslav Martin M Jenkins Glyn G Phillips Dylan D Šamajová Olga O Sedlářová Michaela M Šamaj Jozef J Doležel Jaroslav J Kopecký David D

International journal of molecular sciences 20190322 6

Alien introgressions introduce beneficial alleles into existing crops and hence, are widely used in plant breeding. Generally, introgressed alien chromosomes show reduced meiotic pairing relative to the host genome, and may be eliminated over generations. Reduced pairing appears to result from a failure of some telomeres of alien chromosomes to incorporate into the leptotene bouquet at the onset of meiosis, thereby preventing chiasmate pairing. In this study, we analysed somatic nuclei of rye in ...[more]

PMID: 30909382

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Project description:BackgroundMonitoring alien introgressions in crop plants is difficult due to the lack of genetic and molecular mapping information on the wild crop relatives. The tertiary gene pool of wheat is a very important source of genetic variability for wheat improvement against biotic and abiotic stresses. By exploring the 5Mg short arm (5MgS) of Aegilops geniculata, we can apply chromosome genomics for the discovery of SNP markers and their use for monitoring alien introgressions in wheat (Triticum aestivum L).ResultsThe short arm of chromosome 5Mg of Ae. geniculata Roth (syn. Ae. ovata L.; 2n = 4x = 28, UgUgMgMg) was flow-sorted from a wheat line in which it is maintained as a telocentric chromosome. DNA of the sorted arm was amplified and sequenced using an Illumina Hiseq 2000 with ~45x coverage. The sequence data was used for SNP discovery against wheat homoeologous group-5 assemblies. A total of 2,178 unique, 5MgS-specific SNPs were discovered. Randomly selected samples of 59 5MgS-specific SNPs were tested (44 by KASPar assay and 15 by Sanger sequencing) and 84% were validated. Of the selected SNPs, 97% mapped to a chromosome 5Mg addition to wheat (the source of t5MgS), and 94% to 5Mg introgressed from a different accession of Ae. geniculata substituting for chromosome 5D of wheat. The validated SNPs also identified chromosome segments of 5MgS origin in a set of T5D-5Mg translocation lines; eight SNPs (25%) mapped to TA5601 [T5DL · 5DS-5MgS(0.75)] and three (8%) to TA5602 [T5DL · 5DS-5MgS (0.95)]. SNPs (gsnp_5ms83 and gsnp_5ms94), tagging chromosome T5DL · 5DS-5MgS(0.95) with the smallest introgression carrying resistance to leaf rust (Lr57) and stripe rust (Yr40), were validated in two released germplasm lines with Lr57 and Yr40 genes.ConclusionThis approach should be widely applicable for the identification of species/genome-specific SNPs. The development of a large number of SNP markers will facilitate the precise introgression and monitoring of alien segments in crop breeding programs and further enable mapping and cloning novel genes from the wild relatives of crop plants.

Project description:BackgroundTriticum kiharae (AtAtGGDD, 2n?=?42) is of interest for the improvement of bread wheat as a source of high grain protein and gluten content, as well as resistance to many diseases. The use of T. kiharae for the improvement of T. aestivum L. is complicated by the fact that the homology degree of their genomes is low and this leads to an unbalanced set of chromosomes in the gametes of its first generations and the elimination of some genotypes. The aim of this study was to analyze the nature of alien introgressions and their effect on the cytological stability of hybrids obtained from crossing of bread wheat varieties with T. kiharae.ResultsUsing C-banding, the presence of entire chromosomes of T. kiharae in the karyotypes of hybrid lines (intergenomic substitution 2G/2B), chromosome arms (centric translocation ?2AtS:2AL) and large inserts in the form of terminal translocations involving chromosomes of 1st, 3rd and 5th homoeologous groups of B- and G-genomes were found. Molecular markers revealed short introgression of T. kiharae into the genome of common wheat varieties. The highest introgression frequency was shown for 1A, 1B, 2A, 5B, and 6A chromosomes, while no foreign chromatin was detected in 4A and 4B chromosomes. A high level of cytological stability (a meiotic index of 88.18-93.0%) was noted for the majority of introgression lines. An exception was found for the lines containing the structural reorganization of chromosome 5B, affecting the main genes of chromosome synapsis in terms of their functioning.ConclusionsDuring the stabilization of hybrid karyotypes, the introgression of genetic material from T. kiharae into the genome of T. aestivum occurs in the form of short fragments detectable only by molecular markers and in the form of whole chromosomes (intergenomic substitution) and their large fragments (centric and terminal translocations). The level of cytological stability achieved in F10 by the majority of introgression lines ensures the formation of functional gametes sufficient for the successful reproduction of the obtained hybrids.

Project description:In this study, chromosome painting was developed and used to identify alien chromosomes in TAi-27, a wheat--Thinopyrum intermedium addition line, and the chromosomes of the three different genomes of Th. Intermedium. The smallest alien chromosome of TAi-27 was microdissected and its DNA amplified by DOP-PCR was used as a probe to hybridize with metaphase chromosomes of TAi-27 and Th. intermedium. Results showed that hybridization signals were observed in all regions of a pair of the smallest alien chromosomes and the pericentromeric area of another pair of alien chromosomes in TAi-27, indicating that the probe from microdissected chromosome is species specific. In Th. intermedium, 14 chromosomes had wide and strong hybridization signals distributed mainly on the pericentromere area and 9 chromosomes with narrow and weak signals on the pericentromere area. The remaining chromosomes displayed a very weak or no signal. Sequential FISH/GISH on Th. intermedium chromosomes using the DNAs of microdissected chromosome, Pseudoroegneria spicata (St genome) and pDbH12 (a J(s) genome specific probe) as the probes indicated that the microdissected chromosome belonged to the St genome, three genomes (J(s) , J and St) in Th. intermedium could be distinguished, in which there is no hybridization signal on J genome that is similar to the genome of Th. bessarabicum. Our results showed that the smallest alien chromosomes may represent a truncated chromosome and the repetitive sequence distribution might be similar in different chromosomes within the St genome. However, the repetitive sequence distributions are different within the J(s) genome, within a single chromosome, and among different genomes in Th. intermedium. Our results suggested that chromosome painting could be feasible in some plants and useful in detecting chromosome variation and repetitive sequence distribution in different genomes of polyploidy plants, which is helpful for understanding the evolution of different genomes in polyploid plants.

Dataset Information

Instability of Alien Chromosome Introgressions in Wheat Associated with Improper Positioning in the Nucleus.

Publications

Instability of Alien Chromosome Introgressions in Wheat Associated with Improper Positioning in the Nucleus.

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