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Abstract Benzaldehyde, the simplest aromatic aldehyde, is one of the most wide-spread volatiles that serves as a pollinator attractant, flavor, and antifungal compound. However, the enzyme responsible for its formation in plants remains unknown. Using a combination of in vivo stable isotope labeling, classical biochemical, proteomics and genetic approaches, we show that in petunia benzaldehyde is synthesized via the β-oxidative pathway in peroxisomes by a heterodimeric enzyme consisting of α and β subunits, which belong to the NAD(P)-binding Rossmann-fold superfamily. Both subunits are alone catalytically inactive but, when mixed in equal amounts, form an active enzyme, which exhibits strict substrate specificity towards benzoyl-CoA and uses NADPH as a cofactor. Alpha subunits can form functional heterodimers with phylogenetically distant β subunits, but not all β subunits partner with α subunits, at least in Arabidopsis. Analysis of spatial, developmental and rhythmic expression of genes encoding α and β subunits revealed that expression of the gene for the α subunit likely plays a key role in regulating benzaldehyde biosynthesis. 

The biosynthesis of specialized metabolites is strictly regulated by environmental inputs such as the day–night cycle, but the underlying mechanisms remain elusive. InPetunia hybridacv. Mitchell flowers, the biosynthesis and emission of volatile compounds display a diurnal pattern with a peak in the evening to attract nocturnal pollinators.

Using petunia flowers as a model system, we found that chromatin level regulation, especially histone acetylation, plays an essential role in mediating the day–night oscillation of the biosynthetic gene network of specialized metabolites.

By performing time‐course chromatin immunoprecipitation assays for histone modifications, we uncovered that a specific group of genes involved in the regulation, biosynthesis, and emission of floral volatile compounds, which displays the greatest magnitude in day–night oscillating gene expression, is associated with highly dynamic histone acetylation marks H3K9ac and H3K27ac. Specifically, the strongest oscillating genes featured a drastic removal of histone acetylation marks at night, potentially to shut down the biosynthesis of floral volatile compounds during the morning when they are not needed. Inhibiting daytime histone acetylation led to a compromised evening induction of these genes.

Overall, our study suggested an active role of chromatin modification in the diurnal oscillation of specialized metabolic network.

 

We demonstrate that the discrepancy between the anomalous magnetic moment measured at BNL and Fermilab and the Standard Model prediction could be explained within the context of low-scale gravity and large extra-dimensions. The dominant contribution to (g − 2)µ originates in Kaluza-Klein (KK) excitations (of the lepton gauge boson) which do not mix with quarks (to lowest order) and therefore can be quite light avoiding LHC constraints. We show that the KK contribution to (g − 2)µ,is universal with the string scale entering as an effective cutoff. The KK tower provides a unequivocal distinctive signal which will be within reach of the future muon smasher.