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Characterisation and evolution of chromosome complements of carnivorous Lentibulariaceae

Subject Area Plant Genetics and Genomics
Term from 2012 to 2015
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 212721201
 
Final Report Year 2015

Final Report Abstract

The carnivorous genus Genlisea comprises species with the hitherto smallest angiosperm genomes and displays a ~25-fold infrageneric genome size variation. For a species with a very small genome (G. nigrocaulis: 86 Mbp/1C; 2n=40) and one with an 18-fold larger genome (G. hispidula: 1550 Mbp/1C; 2n=40) the genomes and transcriptomes have been sequenced, with the aim to find reasons and consequences of evolutionary genome size variation. For these two and four other species the genome size and the chromosome number have been determined and their karyotypes were analysed as to their ploidy level, heterochromatin structures, chromosomal repeat and single copy sequence distribution, centromere- and telomere sequences. Genome size evolution in Genlisea occurred bi-directionally in opposite directions (increase by WGD and retroelement dispersion; decrease by deletion-bias in DSB repair and transposon silencing). Because of similar life style and habitat preferences, the >20-fold genome size variation in this genus is most likely selection-neutral, and many repeats seem to be dispensable. Recurrent WGD preserves essential genomic elements during long-term genome shrinking. High mutation frequency and fast evolution are reflected by centromere (tandem repeat vs. retroelements) and even telomere sequence variation (first infrageneric switch, first C in G-rich strand in plant telomeres). FISH with repeats support dysploid chromosome number reduction in the ancestors of mesoallopolyploid species. For three species more than half or all of the chromosome pairs could be discriminated simultaneously by multicolor FISH applying specific pooling strategies and re-probing of chromosome preparations with single copy or tandem repetitive probes. This paved the way for individual addressing of all chromosomes of these species and for future elucidation of their evolutionary fate. The metatranscriptome of the traps of G. nigrocaulis and G. hispidula revealed a microbiome comprising 92 genera of 19 prokaryotic and eukaryotic phyla as prey or as commensals.

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