Abstract
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 [2] = 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.
Highlights
The genus Agave contains more than 200 species and 47 infraspecific categories; 186 taxa are distributed in Mexico, as it is the center of origin of this genus [1]
A. tequilana is commercially propagated by asexual rhizomatous shoots, a procedure which allows for the increase of genetically elite clones with remarkable qualities; and as a consequence, genetic diversity has been reduced though it has been subject to major disease and insect pressure [2,7]
The results showed a variation conserved in the ribosomal DNA (rDNA) copy number per genome and physical distribution of the loci
Summary
The genus Agave contains more than 200 species and 47 infraspecific categories; 186 taxa are distributed in Mexico, as it is the center of origin of this genus [1]. A. tequilana is commercially propagated by asexual rhizomatous shoots, a procedure which allows for the increase of genetically elite clones with remarkable qualities (higher sugar content, size and rapid growth); and as a consequence, genetic diversity has been reduced though it has been subject to major disease and insect pressure [2,7] In this context, the economic importance and vulnerability of Agave crops have led to an increased interest in genetic research of the species [4,8,9]. Agave tequilana has a great economic importance in Mexico in order to produce alcoholic beverages and bioenergy 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. 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
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