Tea plant roots respond to aluminum-induced mineral nutrient imbalances by transcriptional regulation of multiple cation and anion transporters.

BACKGROUND: Tea is one of the most popular non-alcoholic beverages in the world for its flavors and numerous health benefits. The tea tree (Camellia sinensis L.) is a well-known aluminum (Al) hyperaccumulator. However, it is not fully understood how tea plants have adapted to tolerate high concentrations of Al, which causes an imbalance of mineral nutrition in the roots. RESULTS: Here, we combined ionomic and transcriptomic profiling alongside biochemical characterization, to probe the changes of metal nutrients and Al responsive genes in tea roots grown under increasing concentrations of Al. It was found that a low level of Al (~ 0.4 mM) maintains proper nutrient balance, whereas a higher Al concentration (2.5 mM) compromised tea plants by altering micro- and macro-nutrient accumulation into roots, including a decrease in calcium (Ca), manganese (Mn), and magnesium (Mg) and an increase in iron (Fe), which corresponded with oxidative stress, cellular damage, and retarded root growth. Transcriptome analysis revealed more than 1000 transporter genes that were significantly changed in expression upon Al exposure compared to control (no Al) treatments. These included transporters related to Ca and Fe uptake and translocation, while genes required for N, P, and S nutrition in roots did not significantly alter. Transporters related to organic acid secretion, together with other putative Al-tolerance genes also significantly changed in response to Al. Two of these transporters, CsALMT1 and CsALS8, were functionally tested by yeast heterologous expression and confirmed to provide Al tolerance. CONCLUSION: This study shows that tea plant roots respond to high Al-induced mineral nutrient imbalances by transcriptional regulation of both cation and anion transporters, and therefore provides new insights into Al tolerance mechanism of tea plants. The altered transporter gene expression profiles partly explain the imbalanced metal ion accumulation that occurred in the Al-stressed roots, while increases to organic acid and Al tolerance gene expression partly explains the ability of tea plants to be able to grow in high Al containing soils. The improved transcriptomic understanding of Al exposure gained here has highlighted potential gene targets for breeding or genetic engineering approaches to develop safer tea products.

Probiotic strains improve high-fat diet-induced hypercholesterolemia through modulating gut microbiota in ways different from atorvastatin.

Hypercholesterolemia is a major risk factor for cardiovascular disease (CVD). Probiotics are one of the most popular dietary supplements for hypercholesterolemia, but there are questions as to whether there are differences between probiotics and cholesterol-lowering drugs like atorvastatin (ATO) both in effectiveness and in the underlying mechanisms. In this study, the hypocholesterolemia effects of 4 probiotic strains were investigated and compared with ATO, focusing on their impacts on the gut microbiota. A hypercholesterolemia model was established via high-fat diet (HFD) in golden hamsters after which ATO and the 4 probiotics were orally administered individually for 8 weeks. All probiotics were effective, but less than ATO, on body weight, serum parameters (TG, TC, LDL, INS, HbA1c) and expression of inflammatory factors (INF-α, IL-1ß, CRP), with strain JQII-5 being most significant. Besides, these effects were associated with restoration of microbiota dysbiosis induced by HFD. It was worth noting that ATO and probiotics induced different shifts of the gut microbiota in both structure and key phylotypes. Most interestingly, Allobaculum, a HFD-suppressed genus, reported to be involved in alleviating oxidative stress, was enriched by all tested probiotic strains, but not by ATO. Furthermore, Prevotella, also a HFD-suppressed genus, was uniquely reversed by JQII-5. Importantly, most of the alerted genera and reversed genera were found to be correlated with the inflammatory state and serum lipid level. Compared with ATO, the probiotic strains were less effective on body weight, hypercholesterolemia, and inflammation. However, probiotics exert additional favorable effects on the gut microbiota, making them excellent potential complements to cholesterol-lowering drugs like ATO.

The tea plant reference genome and improved gene annotation using long-read and paired-end sequencing data.

Tea is a globally consumed non-alcohol beverage with great economic importance. However, lack of the reference genome has largely hampered the utilization of precious tea plant genetic resources towards breeding. To address this issue, we previously generated a high-quality reference genome of tea plant using Illumina and PacBio sequencing technology, which produced a total of 2,124 Gb short and 125 Gb long read data, respectively. A hybrid strategy was employed to assemble the tea genome that has been publicly released. We here described the data framework used to generate, annotate and validate the genome assembly. Besides, we re-predicted the protein-coding genes and annotated their putative functions using more comprehensive omics datasets with improved training models. We reassessed the assembly and annotation quality using the latest version of BUSCO. These data can be utilized to develop new methodologies/tools for better assembly of complex genomes, aid in finding of novel genes, variations and evolutionary clues associated with tea quality, thus help to breed new varieties with high yield and better quality in the future.

Draft genome sequence of Camellia sinensis var. sinensis provides insights into the evolution of the tea genome and tea quality.

Tea, one of the world's most important beverage crops, provides numerous secondary metabolites that account for its rich taste and health benefits. Here we present a high-quality sequence of the genome of tea, Camellia sinensis var. sinensis (CSS), using both Illumina and PacBio sequencing technologies. At least 64% of the 3.1-Gb genome assembly consists of repetitive sequences, and the rest yields 33,932 high-confidence predictions of encoded proteins. Divergence between two major lineages, CSS and Camellia sinensis var. assamica (CSA), is calculated to ∼0.38 to 1.54 million years ago (Mya). Analysis of genic collinearity reveals that the tea genome is the product of two rounds of whole-genome duplications (WGDs) that occurred ∼30 to 40 and ∼90 to 100 Mya. We provide evidence that these WGD events, and subsequent paralogous duplications, had major impacts on the copy numbers of secondary metabolite genes, particularly genes critical to producing three key quality compounds: catechins, theanine, and caffeine. Analyses of transcriptome and phytochemistry data show that amplification and transcriptional divergence of genes encoding a large acyltransferase family and leucoanthocyanidin reductases are associated with the characteristic young leaf accumulation of monomeric galloylated catechins in tea, while functional divergence of a single member of the glutamine synthetase gene family yielded theanine synthetase. This genome sequence will facilitate understanding of tea genome evolution and tea metabolite pathways, and will promote germplasm utilization for breeding improved tea varieties.