Project description:Somatic variants spontaneously appear during the vegetative multiplication of woody crops. The new white-berried grapevine cultivar Tempranillo Blanco (TB) originally appeared as a bud sport of the black skin-berried Tempranillo Tinto (TT) cultivar. To understand the origin of this variation, TT and TB genomes were sequenced. Structural variation and genetic segregation analyses uncovered that complex chromosome rearrangements consistent with chromothripsis, a catastrophic phenomenon recently described in human cancer, generated the variant genome of TB and the deletion of the color locus functional allele. Loss of heterozygosity and decreased copy number delimited alternating monosomic and disomic fragments in the distal arms of TB’s linkage groups 2 and 5. Hemizygous fragments collectively extended over 8.1 Mb and comprised 313 annotated genes. Clustered breakpoints for complex chromosome rearrangements disrupting linkage groups 2 and 5 were identified and junctions involved unbalanced inter- and intra-chromosome translocations and one unbalanced inversion. Signatures of blunt fusions or microhomology-mediated end joining mechanisms were detected at breakpoint junction flanks. Segregation distortion in TB-derived selfed progeny indicated linkage of rearrangements in a single copy of the affected chromosomes that was barely transmitted. Additionally to berry color loss, these dramatic changes have further viticultural consequences in TB associated to a decreased sexual fitness. Our findings show that chromothripsis spontaneously arise during mitotic multiplication of grapevine, evidencing that this phenomenon could contribute to clonal variation in woody crops and to the evolution of plant genomes. Grapevine GrapeGen GeneChips(R) were used for partial comparative genome hybridization between black-berried cultivars and their respective white-berried somatic variants. Differences in copy number were used to estimate chromosome deletions associated to the loss of berry color.

Project description:Different individuals of the same species are generally thought to have very similar genomes. However, there is growing evidence that structural variation in the form of copy number variation (CNV) and presence-absence variation (PAV) can lead to variation in the genome content of individuals within a species. In order to investigate the potential contribution of CNV and PAV to genomic diversity in maize we used array comparative genomic hybridization (CGH) to compare gene content and copy number variation among 25 diverse maize inbreds 14 genotypes of the wild ancestor of maize, teosinte. The microarray included multiple probes for each of the ~32,500 stringently filtered genes identified in the B73 reference genome. We identified 479 genes exhibiting higher copy number in some genotypes (UpCNV) and 3,410 genes that have either fewer copies or are missing in the genome of at least one genotype relative to B73 (DownCNV/PAV). Many of these DownCNV/PAV are examples of genes that are present in B73 but missing from the genome of several other genotypes. Over 70% of the CNV/PAV examples are identified in multiple genotypes and the majority of events are observed in both maize and teosinte suggesting that these reflect relatively old variants that are not associated with domestication or maize improvement. Many of the genes affected by CNV/PAV are either maize-specific or members of genes families suggesting that the gene loss can be tolerated through buffering by redundant functions encoded elsewhere in the genome. Many plant genomes are relatively large and contain the remnant of whole genome duplications which may provide the ability to tolerate high levels of structural variation. While this structural variation may not result in major qualitative variation due to genetic buffering, it may significantly contribute to quantitative variation. 1-2 replications of 25 maize inbred and 14 teosinte genotypes were hybridized to an array designed from the ~32,400 genes in the maize B73 reference genome.

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