Biology subjects

Bennett, A. A.

Publications and source records attributed to Bennett, A. A..

3 recordsLinked to original sources

bioRxiv2020

Ancestral class-promiscuity as a driver of functional diversity in the BAHD acyltransferase family in plants

Large enzyme families catalyze metabolic diversification by virtue of their ability to use diverse chemical scaffolds. How enzyme families attain such functional diversity is not clear. Here, we addressed this question using BAHD acyltransferases as a model, and identified the routes by which duplication, promiscuity and sequence changes influenced BAHD diversification. This fast-evolving family expanded drastically during land plant evolution from 1-5 copies in algae to [~]100 copies in diploid angiosperm genomes. In vitro characterization of fourteen BAHDs against a substrate panel and compilation of >160 published activities revealed the wide prevalence of promiscuity among BAHDs. Using phylogenetic analysis, we predicted the substrate classes that the ancestral enzymes were likely capable of using prior to land plant origins. While the anthocyanin acylation activity was fixed in BAHDs later near the origin of angiosperms, in vitro testing of BAHDs from non-seed plant lineages suggested that the ability to acylate anthocyanins likely existed promiscuously millions of years prior to its fixation. Motif enrichment analysis in anthocyanin-acylating BAHDs identified two motifs fixed in the largest anthocyanin acylating clade. Molecular dynamic simulations and enzyme kinetics revealed the important role of an active site tryptophan, whose bulkiness, hydrophobicity and aromaticity are critical for anthocyanin acylation. Our results thus describe the molecular processes in robust, evolvable enzymes that drive emergence of functional diversity in enzyme families. One sentence summaryUsing a combination of phylogenetics, biochemistry and protein structure analysis, we investigated how the BAHD acyltransferase family evolved to use a structurally diverse array of substrates.

plant biology↗

bioRxiv2020

Migration through a major Andean ecogeographic disruption as a driver of genotypic and phenotypic diversity in a wild tomato species

The large number of species on our planet arises from the phenotypic variation and reproductive isolation occurring at the population level. In this study, we sought to understand the origins of such population-level variation in defensive acylsugar chemistry and mating systems in Solanum habrochaites - a wild tomato species found in diverse Andean habitats in Ecuador and Peru. Using Restriction-Associated-Digestion Sequencing (RAD-seq) of 50 S. habrochaites accessions, we identified eight population clusters generated via isolation and hybridization dynamics of 4-6 ancestral populations. Estimation of heterozygosity, fixation index, isolation by distance, and migration probabilities, allowed identification of multiple barriers to gene flow leading to the establishment of extant populations. One major barrier is the Amotape-Huancabamba Zone (AHZ) - a geographical feature in the Andes with high endemism, where the mountainous range breaks up into isolated microhabitats. The AHZ was associated with emergence of alleles for novel reproductive and acylsugar phenotypes. These alleles led to the evolution of self-compatibility in the northern populations, where alleles for novel defense-related enzyme variants were also found to be fixed. We identified geographical distance as a major force causing population differentiation in the central/southern part of the range, where S. habrochaites was also inferred to have originated. Findings presented here highlight the role of the diverse ecogeography of Peru and Ecuador in generating new, reproductively isolated populations, and enhance our understanding of the microevolutionary processes that lay a path to speciation.

plant biology↗

bioRxiv2020

Assessing extraction methods and diversity of anthocyanins from purple-fleshed sweet potatoes grown in cooler climates

Anthocyanins are economically valuable phytochemicals of significant relevance to human health. Multiple fruit and vegetable sources for industrial-scale anthocyanin purification exist, however, each source has distinct anthocyanin levels and profiles conferred by modifications to the central anthocyanidin core. In this study, we assessed three purple-fleshed and one orange-fleshed cultivars of sweet potato, with the goal of studying their anthocyanin yield and diversity when this warm-weather crop is grown in cooler, northern latitudes. Comparison of multiple anthocyanin extraction methods revealed acidified ethanol extraction of lyophilized roots as the optimal method, producing a high, average yield of [~]800 mg anthocyanins/100g dry weight. Mass spectrometric analysis of sweet potato extracts identified eighteen high-confidence anthocyanins - all derived from peonidin and cyanidin cores - contributing to over 90% of the total anthocyanin signal. The concentrations of different anthocyanins were variable between the three purple-fleshed cultivars, while low anthocyanin accumulation was observed in the orange-fleshed cultivar. Further assessment of the untargeted high-resolution mass spectrometry data using MS/MS molecular networking revealed existence of low-abundance anthocyanins with delphinidin and pelargonidin cores, as well as over 250 peaks comprising of potential anthocyanins and flavonoids. These results provide a comprehensive insight into anthocyanin yields of purple-fleshed sweet potato grown in the northern latitudes and reveal the large diversity of anthocyanins and flavonoids in this popular crop.

plant biology↗