The evolutionary origin of naturally occurring intermolecular Diels-Alderases from Morus alba.

Biosynthetic enzymes evolutionarily gain novel functions, thereby expanding the structural diversity of natural products to the benefit of host organisms. Diels-Alderases (DAs), functionally unique enzymes catalysing [4 + 2] cycloaddition reactions, have received considerable research interest. However, their evolutionary mechanisms remain obscure. Here, we investigate the evolutionary origins of the intermolecular DAs in the biosynthesis of Moraceae plant-derived Diels-Alder-type secondary metabolites. Our findings suggest that these DAs have evolved from an ancestor functioning as a flavin adenine dinucleotide (FAD)-dependent oxidocyclase (OC), which catalyses the oxidative cyclisation reactions of isoprenoid-substituted phenolic compounds. Through crystal structure determination, computational calculations, and site-directed mutagenesis experiments, we identified several critical substitutions, including S348L, A357L, D389E and H418R that alter the substrate-binding mode and enable the OCs to gain intermolecular DA activity during evolution. This work provides mechanistic insights into the evolutionary rationale of DAs and paves the way for mining and engineering new DAs from other protein families.

Facial expressions can be categorized along the upper-lower facial axis, from a perceptual perspective.

A critical question, fundamental for building models of emotion, is how to categorize emotions. Previous studies have typically taken one of two approaches: (a) they focused on the pre-perceptual visual cues, how salient facial features or configurations were displayed; or (b) they focused on the post-perceptual affective experiences, how emotions affected behavior. In this study, we attempted to group emotions at a peri-perceptual processing level: it is well known that humans perceive different facial expressions differently, therefore, can we classify facial expressions into distinct categories in terms of their perceptual similarities? Here, using a novel non-lexical paradigm, we assessed the perceptual dissimilarities between 20 facial expressions using reaction times. Multidimensional-scaling analysis revealed that facial expressions were organized predominantly along the upper-lower face axis. Cluster analysis of behavioral data delineated three superordinate categories, and eye-tracking measurements validated these clustering results. Interestingly, these superordinate categories can be conceptualized according to how facial displays interact with acoustic communications: One group comprises expressions that have salient mouth features. They likely link to species-specific vocalization, for example, crying, laughing. The second group comprises visual displays with diagnosing features in both the mouth and the eye regions. They are not directly articulable but can be expressed prosodically, for example, sad, angry. Expressions in the third group are also whole-face expressions but are completely independent of vocalization, and likely being blends of two or more elementary expressions. We propose a theoretical framework to interpret the tripartite division in which distinct expression subsets are interpreted as successive phases in an evolutionary chain.

[Quantitative model for patchouli alcohol in Pogostemon cablin by near-infrared spectroscopy].

OBJECTIVE: To establish a near-infrared spectroscopy quantitative model for rapid determination of the patchouli alcohol content in Pogostemon cablin. METHOD: The gas chromatography was adopted for determining the content of patchouli alcohol content in 102 batches of P. cablin samples. Their near-infrared spectrograms were collected and preprocessed by standard normal variate and the first derivative of Savitsky-Golay. The quantitative model of patchouli alcohol content was established by the partial least squares regression analysis. RESULT: According to the correction model established in this study, the root-mean-square error of calibration, the root-mean-square error of prediction and the root-mean-square error of cross-validation of the calibration model for Patchouli alcohol were 0.991 10, 0.012 9, 0.012 8 and 0.033 15, respectively. CONCLUSION: The near-infrared spectroscopy quantitative model established in this study is stable, accurate and reliable for the rapid determination of the content of patchouli alcohol in P. cablin.