Abstract
Simple sequence repeats (SSRs, also known as microsatellites) are known to be mutational hotspots in genomes. DNA rearrangements have also been reported to accompany allopolyploidization. A study of the effect of allopolyploidization on SSR mutation is therefore important for understanding the origin and evolutionary dynamics of SSRs in allopolyploids. Three synthesized double haploid (SynDH) populations were made from 241 interspecific F1 haploid hybrids between Triticum turgidum L. and Aegilops tauschii (Coss.) through spontaneous chromosome doubling via unreduced gametes. Mutation events were studied at 160 SSR loci in the S1 generation (the first generation after chromosome doubling) of the three SynDH populations. Of the 148260 SSR alleles investigated in S1 generation, only one mutation (changed number of repeats) was confirmed with a mutation rate of 6.74 × 10−6. This mutation most likely occurred in the respective F1 hybrid. In comparison with previously reported data, our results suggested that allohexaploidization of wheat did not increase SSR mutation rate.
Highlights
Simple sequence repeats (SSRs, known as microsatellites) are a class of DNA that is composed of short tandem repeats of a basic motif of one to six nucleotides
In the present study we investigated SSR mutation events that existed in the 241 S1 lines from three synthesized double haploid (SynDH)
Our investigation of SSR mutants and the estimation of SSR mutation rate were focused on variation of the repeat numbers at each SSR locus using bulked DNA samples from five randomly selected S1 plants per SynDH line
Summary
Simple sequence repeats (SSRs, known as microsatellites) are a class of DNA that is composed of short tandem repeats of a basic motif of one to six nucleotides. The nature of motif repetition makes SSRs inherently instable and prone to mutation by mechanisms of replication slippage or unequal crossing over [1] Because of their high mutability, SSRs are thought to play a significant role in genome evolution [2]. In the present study we investigated SSR mutation events that existed in the 241 S1 (the first generation after chromosome doubling) lines from three synthesized double haploid (SynDH). Each of these SynDH lines was derived from an independently obtained interspecific F1 haploid hybrid between Triticum turgidum L. and Aegilops tauschii Coss (Table 1; Figure 1). 241 SynDH hexaploid wheat lines represent 241 independent allopolyploidization events and are excellent materials for estimating SSR mutation rate during this important evolutionary event.
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