Molecular regulation of anthocyanin discoloration under water stress and high solar irradiance in pluckable shoots of purple tea cultivar.

MAIN CONCLUSION: During water-deficit stress, antioxidant enzymes use anthocyanin molecules as co-substrates to scavenge for reactive oxygen species leading to reduced anthocyanin content and ultimately loss of purple leaf pigmentation in tea. Anthocyanins are an important class of flavonoids responsible for liquor color and market acceptability of processed tea from the anthocyanin-rich purple tea cultivar 'TRFK 306'. However, the color in pluckable shoots fade and turn green during the dry and hot season, before rapidly reverting back to purple when weather is favorably wet and cool/cold. Our study revealed that loss of purple leaf pigmentation correlated well with reduced precipitation, high soil water-deficit, increased intensity and duration of sunlight and temperature. Richly purple pigmented leaves harvested during the cool, wet conditions recorded significantly higher anthocyanin content compared to faded samples harvested during the dry season. Similarly, individual anthocyanins were affected by seasonal changes with malvidin being the most abundant. Comparative transcriptomics of two RNA-seq libraries, dry/discolored and wet/colored seasons, revealed depression of most metabolic processes related to anthocyanin accumulation in dry conditions. Specifically, transcripts encoding pathway regulators, MYB-bHLH-WD40 (MBW) complex, were repressed possibly contributing to the suppression of late biosynthetic genes of the pathway. Further, suppression of anthocyanin transport genes could be linked to reduced accumulation of anthocyanin in the vacuole during the dry season. However, slight increase in expression of some transporter and reactive oxygen species (ROS) antioxidant genes in the discolored leaf suggests non-enzymatic degradation of anthocyanin, ultimately leading to loss of purple color during the dry season. Based on increased expression of ROS antioxidant genes (especially catalase and superoxide dismutase) in the discolored leaf, we speculate that anthocyanins are used as co-substrates by antioxidant enzymes to scavenge for ROS (especially hydrogen peroxide) that escape from organelles, leading to reduced anthocyanins and loss of pigmentation during the dry season.

Metagenomics survey unravels diversity of biogas microbiomes with potential to enhance productivity in Kenya.

The obstacle to optimal utilization of biogas technology is poor understanding of biogas microbiomes diversities over a wide geographical coverage. We performed random shotgun sequencing on twelve environmental samples. Randomized complete block design was utilized to assign the twelve treatments to four blocks, within eastern and central regions of Kenya. We obtained 42 million paired-end reads that were annotated against sixteen reference databases using two ENVO ontologies, prior to ß-diversity studies. We identified 37 phyla, 65 classes and 132 orders. Bacteria dominated and comprised 28 phyla, 42 classes and 92 orders, conveying substrate's versatility in the treatments. Though, Fungi and Archaea comprised 5 phyla, the Fungi were richer; suggesting the importance of hydrolysis and fermentation in biogas production. High ß-diversity within the taxa was largely linked to communities' metabolic capabilities. Clostridiales and Bacteroidales, the most prevalent guilds, metabolize organic macromolecules. The identified Cytophagales, Alteromonadales, Flavobacteriales, Fusobacteriales, Deferribacterales, Elusimicrobiales, Chlamydiales, Synergistales to mention but few, also catabolize macromolecules into smaller substrates to conserve energy. Furthermore, δ-Proteobacteria, Gloeobacteria and Clostridia affiliates syntrophically regulate PH2 and reduce metal to provide reducing equivalents. Methanomicrobiales and other Methanomicrobia species were the most prevalence Archaea, converting formate, CO2(g), acetate and methylated substrates into CH4(g). Thermococci, Thermoplasmata and Thermoprotei were among the sulfur and other metal reducing Archaea that contributed to redox balancing and other metabolism within treatments. Eukaryotes, mainly fungi were the least abundant guild, comprising largely Ascomycota and Basidiomycota species. Chytridiomycetes, Blastocladiomycetes and Mortierellomycetes were among the rare species, suggesting their metabolic and substrates limitations. Generally, we observed that environmental and treatment perturbations influenced communities' abundance, ß-diversity and reactor performance largely through stochastic effect. Understanding diversity of biogas microbiomes over wide environmental variables and its' productivity provided insights into better management strategies that ameliorate biochemical limitations to effective biogas production.

Kenyan purple tea anthocyanins ability to cross the blood brain barrier and reinforce brain antioxidant capacity in mice.

Studies on antioxidants as neuroprotective agents have been hampered by the impermeability of the blood brain barrier (BBB) to many compounds. However, previous studies have shown that a group of tea flavonoids, the catechins, are brain permeable and neuroprotective. Despite this remarkable observation, there exist no data on the bioavailability and pharmacological benefits of tea anthocyanins (ACNs) in the brain tissue. This study investigated the ability of Kenyan purple tea ACNs to cross the BBB and boost the brain antioxidant capacity. Mice were orally administered with purified and characterized Kenyan purple tea ACNs or a combination of Kenyan purple tea ACNs and coenzyme-Q10 at a dose of 200 mg/kg body weight in an experiment that lasted for 15 days. Twenty-four hours post the last dosage of antioxidants, CO2 was used to euthanize the mice after which the brain was excised and used for various biochemical analyses. Brain extracts were analysed by high-performance liquid chromatography for ACN metabolites and spectrophotometry for cellular glutathione (GSH). Kenyan purple tea ACNs significantly (P < 0.05) raised brain GSH levels implying boost in brain antioxidant capacity. However, co-administration of both antioxidants caused a reduction of these beneficial effects implying a negative interaction. Notably, ACN metabolites were detected in brain tissue of ACN-fed mice. Our results constitute the first demonstration that Kenyan purple tea ACNs can cross the BBB reinforcing the brain's antioxidant capacity. Hence, the need to study them as suitable candidates for dietary supplements that could support antioxidant capacity in the brain and have potential to provide neuroprotection in neurodegenerative conditions.