Pizaine, M. | Search bioRxiv

bioRxiv2025

FMO and CYP monooxygenase families determine the metabolic flux of hydroxylated tryptamine derivatives in barley (Hordum vulgare) following pathogen infection

To counteract pathogenic microorganisms, plants execute a complex resistance response that includes major metabolic reprogramming and production of bioactive defensive compounds. Barley (Hordeum vulgare) is a major cereal crop, but suffers significant yield losses due to pathogen attack every year. Here we use an untargeted metabolomic approach to assess the diversity and shifts in key barley metabolites produced in response to Pyrenophora teres f. teres infection, a hemibiotrophic fungal pathogen and causal agent of net blotch disease. Tryptophan-derived compounds, including tryptamine, serotonin, and a novel indole alkaloid - 2-oxo-tryptamine (2OT) - were among the most significantly induced and abundant compounds, with mass spectrometry imaging revealing that these metabolites accumulate at the site of infection. A transcriptomic approach identified a flavin-containing monooxygenase (FMO), which was functionally characterized as a 2-oxo-tryptamine synthase (2OTS). In addition, a cytochrome P450 (CYP71P10) was characterized as a tryptamine-5-hydroxylase, responsible for serotonin biosynthesis. These characterized genes are tightly co-expressed with genes involved in tryptophan biosynthesis and signify a major metabolic flux towards indolic compounds after infection, potentially serving as bioactive phytoalexins. Additional microbial interactions using a biotrophic fungus (Blumeria hordei; powdery mildew), a hemibiotrophic bacterium (Pseudomonas syringae), and alternative cultivars suggest that these pathways represent a generally activated resistance response in barley. These results provide new insights within the barley defense response relevant for the development of disease resistant traits in cereal crops.

plant biology↗

bioRxiv2025

Use of massive DNA barcoding to monitor biodiversity: a test on forest soil fauna

Biodiversity monitoring primarily focuses on particular taxonomic groups for which identification expertise is widely available, such as vascular plants or birds. As a result, the response of many taxonomic groups to forest management is much less documented. With the advent of low-cost next generation barcoding approaches, it is now possible to envisage monitoring strategies based on molecular approaches, beyond metabarcoding/eDNA strategies that do not give access to species abundances and integrate species presence over largely unknown spatio-temporal scales. In this contribution, we demonstrate the use of massive DNA barcoding - also referred as megabarcoding - as a promising solution to overcome identification difficulties in demanding taxonomic groups. We performed a proof of concept study in a mountainous beech forest in the Massif Central, France. We sampled soil macrofauna at 25 sampling sites and managed to visually identify at the species level 130 out of the 1413 sampled individuals. Using megabarcoding on the 1283 remaining non-identified individuals, we managed to assign 1124 additional individuals to an operational taxonomic species at a competitive cost. We present the summary statistics of barcoding success in the different taxonomic groups encountered and in larvae versus adult individuals. We demonstrate that larvae individuals, which can hardly be visually identified at the species level, make a substantial contribution to overall macrofauna diversity. We finally showcase how this megabarcoding approach provides a concrete avenue for forest biodiversity monitoring, by assessing the cost and labour intensity of this approach.

ecology↗