Beerhues, L. | bioRxiv Science

bioRxiv2026

Natural variation in soybean perception of bacterial quorum-sensing signals shapes primed defense

Plants perceive N-acyl homoserine lactones (AHLs), the quorum-sensing signals of rhizobacteria, and can translate them into a primed state of enhanced inducible immunity. Whether this perception-to-defense translation varies heritably among genotypes is largely unknown. Using soybean (Glycine max) responses to N-3-oxo-tetradecanoyl-L-homoserine lactone (oxo-C14-HSL), with root invasion by the nematode Pratylenchus penetrans as a quantitative challenge revealing the primed state, we tested whether AHL-triggered priming is genotype-dependent. Priming with the oxo-C14-HSL-producing rhizobacterium Ensifer meliloti ExpR+ potentiated defense in the responsive cultivar Primus, reducing nematode invasion (P < 0.001), but not in the weakly responsive Sigalia (P = 0.082). The purified molecule reproduced this contrast, localizing the difference to signal transduction within the plant rather than bacterial colonization. Correspondingly, the phytoalexin glyceollin accumulated in a priming- and challenge-dependent manner in Primus but not Sigalia, the formal signature of priming. Across a Sigalia x Primus recombinant inbred line population and an independent diversity panel, responsiveness was heritable, continuously distributed, and transgressive. Two genome-wide association studies and a cross-population meta-analysis converged on a well-calibrated null, indicating a polygenic or strongly environment-dependent architecture rather than a common-variant, large-effect-size model. Translating a bacterial signal into primed defense is thus a quantitatively varying plant trait.

microbiology↗

bioRxiv2024

Phenylphenalenones and Linear Diarylheptanoid Derivatives are Biosynthesized via Parallel Routes in Musella lasiocarpa, the Chinese Dwarf Banana

Phenylphenalenones (PPs) are complex polycyclic natural products that play an important role in the chemical defense system of banana and plantain (Musaceae). Although suggestions for how plants synthesize the PP scaffold were first proposed more than 50 years ago, no biosynthetic information is yet available at the enzyme level. Here, we use transcriptomic data from seeds of Musella lasiocarpa, the Chinese dwarf banana, to identify five biosynthetic genes involved in the formation of dihydrocurcuminoids. Characterization of the substrate specificities of the enzymes reveals two distinct dihydrocurcuminoid pathways leading to the two types of major aromatic seed metabolites, the PPs and the linear diarylheptanoid derivatives. Furthermore, through multiple rounds of feeding potential intermediates to M. lasiocarpa root protein extract, followed by high-resolution mass spectrometry profiling, product isolation, and NMR-based elucidation, we demonstrate the stepwise conversion of a dihydrocurcumin-type precursor to the PP 4-hydroxylachnanthocarpone. In contrast to the commonly hypothesized Diels-Alder cyclization mechanism, we propose an unexpected two-step cyclization route to the PP scaffold.

biochemistry↗