Towards Plant Species Identification in Complex Samples: A Bioinformatics Pipeline for the Identification of Novel Nuclear Barcode Candidates

<div><p>Monitoring of the food chain to fight fraud and protect consumer health relies on the availability of methods to correctly identify the species present in samples, for which DNA barcoding is a promising candidate. The nuclear genome is a rich potential source of barcode targets, but has been relatively unexploited until now. Here, we show the development and use of a bioinformatics pipeline that processes available genome sequences to automatically screen large numbers of input candidates, identifies novel nuclear barcode targets and designs associated primer pairs, according to a specific set of requirements. We applied this pipeline to identify novel barcodes for plant species, a kingdom for which the currently available solutions are known to be insufficient. We tested one of the identified primer pairs and show its capability to correctly identify the plant species in simple and complex samples, validating the output of our approach.</p></div

Species detection in various samples using the 23579-aaa barcoding primers.

<p>The tested samples were (A) Purchased maize (<i>Zea mays</i>) DNA. (B) Purchased soya (<i>Glycine max</i>) DNA. (C) A leaf from a rice (<i>Oryza sativa</i>) plant. (D) Fresh strawberries from the supermarket (<i>Fragaria x ananassa</i>). (E) A commercial pack of fruit and cereal muesli. The results are shown on a simplified taxonomy line, with the number of NGS reads assigned to that specific location as a blue circle whose area is proportional to the numerical value. The values in parenthesis represent the (number of clusters:total number of reads).</p

Bioinformatics pipeline for the identification of DNA barcodes in the nuclear genome.

<p>Scheme representing the flow of the different steps in the bioinformatics pipeline designed to process input sequences (top left) in order to output potential primer pairs amplifying novel DNA barcoding targets (bottom right). See text and Supporting Information for details.</p