A quantitative PCR approach for determining the ribosomal DNA copy number in the genome of Agave tequila Weber|
Rubio-Piña, Jorge; Quiroz-Moreno, Adriana & Sánchez-Teyer, L. Felipe
Background: Agave tequilana has a great economic importance in Mexico in order to produce alcoholic beverages
and bioenergy. However, in this species the structure and organization of the rDNAs in the genome are limited,
and it represents an obstacle both in their genetic research and improvement as well. rDNA copy number
variations per eukaryotic genome have been considered as a source of genetic rearrangements. In this study,
the copy number of 18S and 5S rDNAs in the A. tequilana genome was estimated, and an absolute quantitative
qPCR assay and genome size was used. In addition, an association between the rDNAs copy number and
physical mapping was performed to confirm our results.
Results: The analysis were successfully applied to determine copy number of 18S and 5S rDNAs in A. tequilana
genome, showing high reproducibility with coefficient of variation (CV) values of 0.014–0.0129%, respectively. A
variation of 51 times in the copy number the 18s regarding 5s rDNA was found, thus contributing to genome
size of 1.47 and 8.38 × 10-3%, respectively. Similarly, data show a linear relationship (R  = 0.992) between
rDNA copy number and the detected signals for each of the loci by FISH. The comparison of the rDNA copy
number of agave showed differential relationship with other organisms and it may be due to evolutionary ecology.
Conclusions: Results show that the proposed method a) can correctly detect the rDNA copy number, b) could be
used as species-specific markers and c) might help in understanding the genetic diversity, genome organization
and evolution of this species.
Agave tequilana; Copy number; Fluorescent in situ hybridization; Ribosomal DNA; Quantitative PCR