A new DNA marker in the trnL intron region distinguishes the two cactus species Lophophora williamsii (which contains the psychotropic agent mescaline) and Lophophora diffusa. The marker is a variable number tandem repeat (VNTR) where one repeat unit (13 nucleotides) occurs in L. williamsii and two in L. diffusa. A TaqMan genotyping assay using two probes detected the marker with high sensitivity (detection limits of 0.000063 ng and 0.000066 ng). Testing 16 crime-scene samples presumed to be L. williamsii matched results from gas chromatography-mass spectrometry, confirming the method's forensic applicability for species identification.
A full-length transcriptome of Lophophora williamsii (peyote) was generated using single-molecule real-time PCR and PacBio Iso-Seq, yielding 2,839,819 base pairs of long reads and 70,945 unigenes. Known genes in the mescaline biosynthetic pathway were confirmed, including 6 tyrosine decarboxylases, 1 tyrosine/DOPA decarboxylase, 215 O-methyltransferases, and 129 hydroxylases. Gene Ontology analysis identified 2903 biological processes, 695 cellular components, and 1766 molecular functions. KEGG pathway analysis linked phenylpropanoid and isoquinoline biosynthesis to mescaline production. Illumina Nova sequencing compared gene expression between mescaline-positive and mescaline-negative specimens to establish a candidate gene pool. The findings call for re-evaluation of forensic methods and legal regulations for newly identified L. williamsii specimens.