A single amino acid substitution converts a histidine decarboxylase to an imidazole acetaldehyde synthase

A Metabolome Analysis and the Immunity of Phlomis purpurea against Phytophthora cinnamomi

Phlomis purpurea grows spontaneously in the southern Iberian Peninsula, namely in cork oak (Quercus suber) forests. In a previous transcriptome analysis, we reported on its immunity against Phytophthora cinnamomi. However, little is known about the involvement of secondary metabolites in the P. purpurea defense response. It is known, though, that root exudates are toxic to this pathogen. To understand the involvement of secondary metabolites in the defense of P. purpurea, a metabolome analysis was performed using the leaves and roots of plants challenged with the pathogen for over 72 h. The putatively identified compounds were constitutively produced. Alkaloids, fatty acids, flavonoids, glucosinolates, polyketides, prenol lipids, phenylpropanoids, sterols, and terpenoids were differentially produced in these leaves and roots along the experiment timescale. It must be emphasized that the constitutive production of taurine in leaves and its increase soon after challenging suggests its role in P. purpurea immunity against the stress imposed by the oomycete. The rapid increase in secondary metabolite production by this plant species accounts for a concerted action of multiple compounds and genes on the innate protection of Phlomis purpurea against Phytophthora cinnamomi. The combination of the metabolome with the transcriptome data previously disclosed confirms the mentioned innate immunity of this plant against a devastating pathogen. It suggests its potential as an antagonist in phytopathogens' biological control. Its application in green forestry/agriculture is therefore possible.

Immobilizing diamine oxidase on electroactive phase-change microcapsules to construct thermoregulatory smart biosensor for enhancing detection of histamine in foods

Aiming at enhancing the biosensing detection of histamine in foods at high temperature, we developed a thermoregulatory biosensor based on diamine oxidase-immobilized phase-change microcapsules consisting of an n-docosane core, a TiO₂ shell, and an electroactive polyaniline/ZnO composite coating layer. The microcapsules exhibit a satisfactory latent heat capacity of over 112 J/g for thermo-temperature regulation. Through an innovative integration of electroactive phase-change microcapsules and biological enzyme in the working electrode, the biosensor obtained a thermoregulatory function through reversible phase transitions by the n-docosane core under high-temperature environments. This enables the biosensor to achieve a higher response sensitivity of 28.57 µA⋅mM^-1⋅cm^-2 and a lower detection limit of 0.473 µmol/L at the high assay temperatures compared to conventional histamine biosensors. With enhanced electrochemical biosensing performance through in-situ thermo-temperature regulation, the smart biosensor developed in this study has found practical applications for high-sensitive detection and high-accurate quantitive determination of histamine in foods across a broad temperature range.