Plants perceive and respond to environmental stresses with complex mechanisms that are often associated with the activation of antioxidant defenses. A genetic screen aimed at isolating oxidative stress-tolerant lines of Arabidopsis thaliana has identified oxt1, a line that exhibits improved tolerance to oxidative stress and elevated temperature but displays no apparent deleterious growth effects under non-stress conditions. Oxt1 harbors a mutation that arises from the altered expression of a gene encoding adenine phosphoribosyltransferase (APT1), an enzyme that converts adenine to adenosine monophosphate (AMP), indicating a link between purine metabolism, whole-plant growth responses, and stress acclimation. The oxt1 mutation results in decreased APT1 expression that leads to reduced enzymatic activity. Correspondingly, oxt1 plants possess elevated levels of adenine. Decreased APT enzyme activity directly correlates with stress resistance in transgenic lines that ectopically express APT1. The metabolic alteration in oxt1 plants also alters the expression of several antioxidant defense genes and the response of these genes to oxidative challenge. Finally, it is shown that manipulation of adenine levels can induce stress tolerance to wild-type plants. Collectively, these results show that alterations in cellular adenine levels can trigger stress tolerance and improve growth, leading to increases in plant biomass. The results also suggest that adenine might play a part in the signals that modulate responses to abiotic stress and plant growth.

In Thailand, there are four Mitragyna species; M. speciosa, M. hirsuta, M. diversifolia, and M. rotundifolia. One, M. speciosa, is a narcotic plant and has medicinal importance for its opium-like effect. Since the use of M. speciosa has been forbidden in Thailand, the leaves of M. diversifolia or others are frequently used as substitutes but are not considered as effective. Therefore, accurate authentication of M. speciosa is essential for both medicinal and forensic purposes. The nucleotide sequences of internal transcribed spacers (ITS) and the 5.8S coding region of nuclear ribosomal DNA (rDNA) of the Mitragyna species were analyzed. The whole length of ITS1-5.8S-ITS2 region was 608 bp in M. speciosa, 607 bp in the other species. Nineteen sites of nucleotide substitutions and 3 sites of 1-bp indels were observed, and M. speciosa showed specific sequence differed from the others. Based on the ITS sequences, a distinctive site recognized by a restriction enzyme XmaI in M. speciosa was found and then PCR-restriction fragment length polymorphism (RFLP) analysis was established to differentiate M. speciosa from the others. By the method, a 409-bp PCR fragment of ITS1-5.8S (partial) rDNA region from M. speciosa was cleaved into two fragments of 119 bp and 290 bp while the other species remained undigested. This method provides an effective and accurate identification of M. speciosa.

Traditional medicines are widely traded across the globe and have received considerable attention in the recent past, with expectations of heightened demand in the future. However, there are increasing global concerns over admixture, which can affect the quality, safety, and efficacy of herbal medicinal products. In this study, we aimed to use DNA metabarcoding to identify 39 Thai herbal products on the Thai National List of Essential Medicines (NLEM) and assess species composition and admixture. Among the products, 24 samples were in-house-prepared formulations, and 15 samples were registered formulations. In our study, DNA metabarcoding analysis using ITS2 and rbcL barcode regions were employed to identify herbal ingredients mentioned in the products. The nuclear region, ITS2, was able to identify herbal ingredients in the products at the genus- and family-levels in 55% and 63% of cases, respectively. The chloroplast gene, rbcL, enabled genus- and family-level identifications in 58% and 73% of cases, respectively. In addition, plant species were detected in larger numbers (Family identified, absolute %) in registered herbal products than in in-house-prepared formulations. The level of fidelity increases concerns about the reliability of the products. This study highlights that DNA metabarcoding is a useful analytical tool when combined with advanced chemical techniques for the identification of plant species in highly processed, multi-ingredient herbal products.