Abstract:

The ribosomal DNA (rDNA) repeats of more and more species have been found to be polymorphic in the genome, and the understanding of this polymorphism is conducive not only to eliminating potential chaos in the metagenomic analysis (MGA), but also to providing rich information on rDNA evolution. In this study, the MGA previously used for the study of environmental microbial diversity was improved and extended to detect the intragenomic polymorphism (IGP) of rDNA in three species of Camellia L. The 3′‐end region of 26S rDNA of three individuals was amplified using degenerate primer pairs. Three annealing temperatures were applied to obtain as many ribotypes as possible, and equimolar amplicons from the three species were then pooled and sequenced using the Illumina MiSeq platform. An incredibly high level of IGP of rDNA was found in all three species. Nearly all of the ribotypes detected from this study were rDNA pseudogenes, and most of them have existed for a long time in the genome, with some generated from several rapid expansions. Our procedure provided an effective technique for detection of IGP of rDNA, and the particular evolutionary information of rDNAs in Camellia was also exploited.

Key words: 26S rDNA, Camellia, intra-genomic polymorphism, Miseq sequencing, pseudogene.