Cool Temperature Enhances Growth, Ferulic Acid and Flavonoid Biosynthesis While Inhibiting Polysaccharide Biosynthesis in Angelica sinensis

Angelica sinensis, a perennial herb that produces ferulic acid and phthalides for the treatment of cardio-cerebrovascular diseases, prefers growing at an altitude of 1800–3000 m. Geographical models have predicted that high altitude, cool temperature and sunshade play determining roles in geo-authentic formation. Although the roles of altitude and light in yield and quality have been investigated, the role of temperature in regulating growth, metabolites biosynthesis and gene expression is still unclear. In this study, growth characteristics, metabolites contents and related genes expression were investigated by exposing A. sinensis to cooler (15 °C) and normal temperatures (22 °C). The results showed that plant biomass, the contents of ferulic acid and flavonoids and the expression levels of genes related to the biosynthesis of ferulic acid (PAL1, 4CLL4, 4CLL9, C3H, HCT, CCOAMT and CCR) and flavonoids (CHS and CHI) were enhanced at 15 °C compared to 22 °C. The contents of ligustilide and volatile oils exhibited slight increases, while polysaccharide contents decreased in response to cooler temperature. Based on gene expression levels, ferulic acid biosynthesis probably depends on the CCOAMT pathway and not the COMT pathway. It can be concluded that cool temperature enhances plant growth, ferulic acid and flavonoid accumulation but inhibits polysaccharide biosynthesis in A. sinensis. These findings authenticate that cool temperature plays a determining role in the formation of geo-authentic and also provide a strong foundation for regulating metabolites production of A. sinensis.

Microtubule-associated IQD9 guides cellulose synthase velocity to shape seed mucilage

Arabidopsis seeds release large capsules of mucilaginous polysaccharides, which are shaped by an intricate network of cellulosic microfibrils. Cellulose synthase complexes is guided by the microtubule cytoskeleton, but it is unclear which proteins mediate this process in the seed coat epidermis (SCE). Using reverse genetics, we identified IQ67 DOMAIN 9 (IQD9) and KINESIN LIGHT CHAIN-RELATED 1 (KLCR1) as two highly expressed genes during seed development and comprehensively characterized their roles for cell wall polysaccharide biosynthesis and cortical microtubule (MT) organization. Mutations in IQD9 as well as in KLCR1 lead to compact mucilage capsules with aberrant cellulose distribution, which can be rescued by transgene complementation. Double mutant analyses revealed that their closest paralogs (IQD10 and KLCR2, respectively) are not required for mucilage biosynthesis. IQD9 physically interacts with KLCR1 and localizes to cortical MTs to maintain their organization in SCE cells. Similar to the previously identified TONNEAU1 (TON1) RECRUITING MOTIF 4 (TRM4) protein, IQD9 is required to maintain the velocity of cellulose synthases. Our results demonstrate that IQD9, KLCR1 and TRM4 are MT-associated proteins that are required for seed mucilage architecture. This study provides the first direct evidence that members of the IQD, KLCR and TRM families have overlapping roles in guiding the distribution of cell wall polysaccharides. Therefore, SCE cells provide an attractive system to further decipher the complex genetic regulation of polarized cellulose deposition.

Acinetobacter baumannii regulates its stress responses via the BfmRS two-component regulatory system

Acinetobacter baumannii is a common nosocomial pathogen that utilizes numerous mechanisms to aid its survival in both the environment and in the host. Coordination of such mechanisms requires an intricate regulatory network. We report here that A. baumannii can directly regulate several stress-related pathways via the two-component regulatory system, BfmRS. Similar to previous studies, results from transcriptomic analysis showed that mutation of the BfmR response regulator causes dysregulation of genes required for the oxidative stress response, the osmotic stress response, the misfolded protein/heat shock response, Csu pili/fimbriae production, and capsular polysaccharide biosynthesis. We also found that the BfmRS system is involved in controlling siderophore biosynthesis and transport, and type IV pili production. We provide evidence that BfmR binds to various stress-related promoter regions and show that BfmR alone can directly activate transcription of some stress-related genes. Additionally, we show that the BfmS sensor kinase acts as a BfmR phosphatase to negatively regulate BfmR activity. This work highlights the importance of the BfmRS system in promoting survival of A. baumannii . Importance Acinetobacter baumannii is a nosocomial pathogen that has extremely high rates of multidrug resistance. This organism’s ability to endure stressful conditions is a key part of its ability to spread in the hospital environment and cause infections. Unlike other members of the γ-proteobacteria, A. baumannii does not encode a homolog of the RpoS sigma factor to coordinate its stress response. Here, we demonstrate that the BfmRS two-component system directly controls the expression of multiple stress resistance genes. Our findings suggest that BfmRS is central to a unique scheme of general stress response regulation by A. baumannii .

Systematic analysis of the lysine malonylome in Sanghuangporus sanghuang

Background Sanghuangporus sanghuang is a well-known traditional medicinal mushroom associated with mulberry. Despite the properties of this mushroom being known for many years, the regulatory mechanisms of bioactive compound biosynthesis in this medicinal mushroom are still unclear. Lysine malonylation is a posttranslational modification that has many critical functions in various aspects of cell metabolism. However, at present we do not know its role in S. sanghuang. In this study, a global investigation of the lysine malonylome in S. sanghuang was therefore carried out. Results In total, 714 malonyl modification sites were matched to 255 different proteins. The analysis indicated that malonyl modifications were involved in a wide range of cellular functions and displayed a distinct subcellular localization. Bioinformatics analysis indicated that malonylated proteins were engaged in different metabolic pathways, including glyoxylate and dicarboxylate metabolism, glycolysis/gluconeogenesis, and the tricarboxylic acid (TCA) cycle. Notably, a total of 26 enzymes related to triterpene and polysaccharide biosynthesis were found to be malonylated, indicating an indispensable role of lysine malonylation in bioactive compound biosynthesis in S. sanghuang. Conclusions These findings suggest that malonylation is associated with many metabolic pathways, particularly the metabolism of the bioactive compounds triterpene and polysaccharide. This paper represents the first comprehensive survey of malonylation in S. sanghuang and provides important data for further study on the physiological function of lysine malonylation in S. sanghuang and other medicinal mushrooms.

De novo Sequencing and Comparative Transcriptome Analyses Provide First Insights Into Polysaccharide Biosynthesis During Fruiting Body Development of Lentinula edodes

Polysaccharides separated from Lentinula edodes are well known for their medicinal properties. However, the precise molecular mechanisms of polysaccharide biosynthesis in L. edodes remain unclear. In this study, the fruiting bodies of L. edodes in four developmental stages with significant differences in polysaccharide yield were collected, and the characteristics of polysaccharides were studied. De novo sequencing and comparative transcriptomic analysis were performed by using high-throughput Illumina RNA-sequencing. KS1P30, KS2P30, KS3P30, and KS4P30 were obtained from the four developmental stages, respectively, by hot water extraction and 30% ethanol precipitation. These four polysaccharides had good immune activity in vitro; all of them were β-glucopyranose with a high molecular weight. Glucose was the main monosaccharide component of these polysaccharides. High-quality clean reads (57.88, 53.17, 53.28, and 47.56 million for different growth stages) and mapping ratios ranging from 84.75 to 90.11% were obtained. In total, 11,493 (96.56%) unigenes and 18,924 (97.46%) transcripts were successfully annotated in five public databases. The biosynthetic pathway and related genes of LEFP30 were mined. The molecular mechanism of LEFP30 yield change in the different developmental stages was predicted. The results provide some insights into the possible mechanisms involved in the biosynthetic pathway of this kind of polysaccharide in L. edodes fruiting bodies. They also indicate that candidate genes can be used as important resources for biotechnology and molecular breeding to regulate L. edodes fruiting body polysaccharide biosynthesis.

Epidemiological and genomic characteristics of Acinetobacter baumannii from different infection sites using comparative genomics

Background Acinetobacter baumannii is a common nosocomial pathogen that poses a huge threat to global health. Owing to the severity of A. baumannii infections, it became necessary to investigate the epidemiological characteristics of A. baumannii in Chinese hospitals and find the reasons for the high antibiotic resistance rate and mortality. This study aimed to investigate the epidemiologic and genetic characteristics of A. baumannii isolated from patients with hospital acquired pneumonia (HAP), bloodstream infection (BSI) and urinary tract infection (UTI) in China and uncover potential mechanisms for multi-drug resistance and virulence characteristics of A. baumannii isolates. Results All isolates were classified into two primary clades in core gene-based phylogenetic relationship. Clonal complex 208 (CC208) mainly consisted of ST195 (32 %) and ST208 (24.6 %). CC208 and non-CC208 isolates had carbapenem resistance rates of 96.2 and 9.1 %, respectively. Core genes were enriched in ‘Amino acid transport and metabolism’, ‘Translation’, ‘Energy production and conversion’, ‘Transcription’, ‘Inorganic ion transport and metabolism’ and ‘Cell wall/membrane/envelope synthesis’. Most isolates possessed virulence factors related to polysaccharide biosynthesis, capsular polysaccharide synthesis and motility. Eleven isolates belong to ST369 or ST191 (oxford scheme) all had the virulence factor cap8E and it had a higher positive rate in UTI (35.3 %) than in BSI (18.9 %) and HAP (12.9 %). ABGRI1 antibiotic resistance islands were responsible for streptomycin, tetracycline and sulfonate resistance. The blaOXA−23 gene was the most probable cause for carbapenem resistance, although the blaOXA−66 gene with nonsynonymous SNPs (F82L, I129L) was not. Conclusions A. baumannii is a genomically variable pathogen that has the potential to cause a range of infectious diseases. There is high proportion of carbapenem resistance in isolates from all three infection sites (HAP, BSI and UTI), which can be attributed to the blaOXA−23 gene. CC208 is the predominant clone in blaOXA−23-carrying A. baumannii that should be monitored. Virulence factors involving bacteria motility and polysaccharide biosynthesis which are widespread in clinical A. baumannii strains deserve our attention.

Pangenome analysis and virulence profiling of Streptococcus intermedius

Background Streptococcus intermedius, a member of the S. anginosus group, is a commensal bacterium present in the normal microbiota of human mucosal surfaces of the oral, gastrointestinal, and urogenital tracts. However, it has been associated with various infections such as liver and brain abscesses, bacteremia, osteo-articular infections, and endocarditis. Since 2005, high throughput genome sequencing methods enabled understanding the genetic landscape and diversity of bacteria as well as their pathogenic role. Here, in order to determine whether specific virulence genes could be related to specific clinical manifestations, we compared the genomes from 27 S. intermedius strains isolated from patients with various types of infections, including 13 that were sequenced in our institute and 14 available in GenBank. Results We estimated the theoretical pangenome size to be of 4,020 genes, including 1,355 core genes, 1,054 strain-specific genes and 1,611 accessory genes shared by 2 or more strains. The pangenome analysis demonstrated that the genomic diversity of S. intermedius represents an “open” pangenome model. We identified a core virulome of 70 genes and 78 unique virulence markers. The phylogenetic clusters based upon core-genome sequences and SNPs were independent from disease types and sample sources. However, using Principal Component analysis based on presence/ absence of virulence genes, we identified the sda histidine kinase, adhesion protein LAP and capsular polysaccharide biosynthesis protein cps4E as being associated to brain abscess or broncho-pulmonary infection. In contrast, liver and abdominal abscess were associated to presence of the fibronectin binding protein fbp54 and capsular polysaccharide biosynthesis protein cap8D and cpsB. Conclusions Based on the virulence gene content of 27 S. intermedius strains causing various diseases, we identified putative disease-specific genetic profiles discriminating those causing brain abscess or broncho-pulmonary infection from those causing liver and abdominal abscess. These results provide an insight into S. intermedius pathogenesis and highlights putative targets in a diagnostic perspective.