Retigeric Acid B Attenuates the Virulence of Candida albicans via Inhibiting Adenylyl Cyclase Activity Targeted by Enhanced Farnesol Production

Candida albicans, the most prevalent fungal pathogen, undergoes yeast-to-hyphal switch which has long been identified as a key fungal virulence factor. We showed here that the lichen-derived small molecule retigeric acid B (RAB) acted as an inhibitor that significantly inhibited the filamentation of C. albicans, leading to the prolonged survival of nematodes infected by C. albicans. Quantitative real-time PCR analysis and intracellular cAMP measurement revealed RAB regulated the Ras1-cAMP-Efg1 pathway by reducing cAMP level to inhibit the hyphae formation. Confocal microscopic observation showed RAB induced the expression of Dpp3, synthesizing more farnesol, which was confirmed by gas chromatography-mass spectroscopy detection. An adenylyl cyclase activity assay demonstrated RAB could repress the activity of Cdc35 through stimulating farnesol synthesis, thus causing a decrease in cAMP synthesis, leading to retarded yeast-to-hyphal transition. Moreover, reduced levels of intracellular cAMP resulted in the inhibition of downstream adhesins. Together, these findings indicate that RAB stimulates farnesol production that directly inhibits the Cdc35 activity, reducing the synthesis of cAMP and thereby causing the disruption of the morphologic transition and attenuating the virulence of C. albicans. Our work illustrates the underlying mechanism of RAB-dependent inhibition of the yeast-to-hyphal switch and provides a potential application in treating the infection of C. albicans.     

cis-Clerodane diterpenoids from the Chinese liverwort Scapania parva Steph.

Three undescribed cis-clerodane lactones, scapanialides A–C (1–3), and a new cis-clerodane furano-diterpenoid, scaparvin F (4), were isolated from the Chinese liverwort Scapania parva Steph. Scapanialide B (2) is the first cis-clerodane diterpenoid with a bicyclo[5.4.0]undecane skeleton from liverworts. Their structures including the absolute configurations were determined by extensive analysis of multidimensional NMR spectroscopy and TDDFT CD calculations, together with crystal X-ray diffraction measurements. The cytotoxicity of compounds 1–4 was preliminary tested against the Hela and MCF-7 cell lines.     

Preparation of inulin and phenols-rich dietary fibre powder from burdock root

The simultaneous ultrasonic/microwave assisted extraction (UMAE) of inulin and production of phenols-rich dietary fibre powder from burdock root was studied. It was found that UMAE required a much shorter extraction time than conventional stirring extraction. And the recovery of inulin increased with the increase of microwave power as well as solvent to solid ratio. A comparison of scanning electron microscopy images of raw and simultaneous ultrasonic/microwave treated burdock root indicated microfractures and disruption of cell walls in burdock root flakes. The dietary fibre powder prepared from the residue of burdock root after inulin extraction was rich in phenols (302.62 mg GAE/100 g powder). The results showed that drying temperature in the selected range did not significantly affect the hydration properties. The relatively high water retention capacity, swelling capacity and oil-holding capacity of the dietary fibre powder indicated its broad use as a modifier of properties of formulated products.     

Statistical challenges of evaluating diversity patterns across environmental gradients in mega‐diverse communities

Ibanez et al. (Journal of Vegetation Science, this issue) applied sample size‐ and coverage‐based rarefaction to analyse the elevational richness pattern in New Caledonian tree communities. We comment on the statistical assumptions behind rarefaction/extrapolation and suggest pooling small plot data to effectively assess/detect the diversity pattern. Broadening the analysis to include abundance‐sensitive diversity measures and phylogenetic information can provide important additional insights.     

Mechanistic insights into the effect of imidazolium ionic liquid on lipid production by <Emphasis Type="Italic">Geotrichum fermentans</Emphasis>

Background

Ionic liquid (IL) pretreatment has emerged as a promising technique that enables complete utilization of lignocellulosic biomass for biofuel production. However, imidazolium IL has recently been shown to exhibit inhibitory effect on cell growth and product formation of industrial microbes, such as oleaginous microorganisms. To date, the mechanism of this inhibition remains largely unknown.

Results

In this study, the feasibility of [Bmim][OAc]-pretreated rice straw hydrolysate as a substrate for microbial lipid production by Geotrichum fermentans, also known as Trichosporon fermentans, was evaluated. The residual [Bmim][OAc] present in the hydrolysate caused a reduction in biomass and lipid content (43.6 and 28.1%, respectively) of G. fermentans, compared with those of the control (7.8 g/L and 52.6%, respectively). Seven imidazolium ILs, [Emim][DEP], [Emim]Cl, [Amim]Cl, [Bmim]Cl, [Bzmim]Cl, [Emim][OAc], and [Bmim][OAc], capable of efficient pretreatment of lignocellulosic biomass were tested for their effects on the cell growth and lipid accumulation of G. fermentans to better understand the impact of imidazolium IL on the lipid production. All the ILs tested inhibited the cell growth and lipid accumulation. In addition, both the cation and the anion of IL contributed to IL toxicity. The side chain of IL cations showed a clear impact on toxicity. On examining IL anions, [OAc]^? was found to be more toxic than those of [DEP]^? and Cl^?. IL exhibited its toxicity by inhibiting sugar consumption and key enzyme (malic enzyme and ATP-citrate lyase) activities of G. fermentans. Cell membrane permeability was also altered to different extents in the presence of various ILs. Scanning electron microscopy revealed that IL induces fibrous structure on the surface of G. fermentans cell, which might represent an adaptive mechanism of the yeast to IL.

Conclusions

This work gives some mechanistic insights into the impact of imidazolium IL on the cell growth and lipid accumulation of oleaginous yeast, which is important for IL integration in lignocellulosic biofuel production, especially for microbial lipid production.

     

Insights into the conformational flexibility of Bruton's tyrosine kinase from multiple ligand complex structures

Bruton's tyrosine kinase (BTK) plays a key role in B cell receptor signaling and is considered a promising drug target for lymphoma and inflammatory diseases. We have determined the X-ray crystal structures of BTK kinase domain in complex with six inhibitors from distinct chemical classes. Five different BTK protein conformations are stabilized by the bound inhibitors, providing insights into the structural flexibility of the Gly-rich loop, helix C, the DFG sequence, and activation loop. The conformational changes occur independent of activation loop phosphorylation and do not correlate with the structurally unchanged WEI motif in the Src homology 2-kinase domain linker. Two novel activation loop conformations and an atypical DFG conformation are observed representing unique inactive states of BTK. Two regions within the activation loop are shown to structurally transform between 3(10)- and α-helices, one of which collapses into the adenosine-5'-triphosphate binding pocket. The first crystal structure of a Tec kinase family member in the pharmacologically important DFG-out conformation and bound to a type II kinase inhibitor is described. The different protein conformations observed provide insights into the structural flexibility of BTK, the molecular basis of its regulation, and the structure-based design of specific inhibitors.     

山茶属五种植物叶片解剖特征及与光合生理相关性研究

利用扫描电子显微镜观察山茶属（ＣａｍｅｌｌｉａＬｉｎｎ．）五种植物叶片解剖特征,并与光合生理相关性进行分析。实验选择的五种植物均为Ｃ３植物,其中小黄花茶（ＣａｍｅｌｌｉａｌｕｔｅｏｆｌｏｒａＹ．Ｋ．Ｌｉ）和四球茶（Ｃ．ｔａｃｈａｎｇｅｎｓｉｓＦ．Ｃ．Ｚｈａｎｇ）为阴性植物．叶绿素含量较高;咸宁短柱茶（Ｃ．ｓａｌｕｅｎｅｎｓｉｓＳｔａｐｆ．ｅｘＢｅａｎ．）为偏阴性植物,叶绿素含量较低;美丽红山茶（Ｃ．ｄｅｌｉｃａｔａＹ．Ｋ．Ｌｉ）和狭叶瘤果茶（Ｃ．ｎｅｒｉｉｆｏｌｉａＣｈａｎｇ）则属于半阴性植物。它们的光合生理指标值差异取决于叶片解剖特征的差异;与光补偿点,光饱和点,净光合速率（Ｐｎ）,光呼吸速率（Ｐｒ）,暗呼吸速率（Ｄｒ）相关性最密切的解剖指标是栅栏组织厚度、栅栏组织中的细胞层数、栅栏细胞内的叶绿体数,栅栏组织厚与叶厚的比值、与栅栏细胞粗度的比值、与海绵组织厚度的比值．叶片上表皮厚、上表皮角质层厚及下表皮气孔密度亦与上述光合生理指标呈弱正相关,叶片大小、气孔器大小及气孔口长则与上述光合生理指标呈弱负相关;下表皮厚、海绵组织厚度及栅栏细胞内叶绿体大小与各项光合生理指标几乎无关。该五种植物的叶片解剖和光合生理特     

Host-recognition kairomone from Sogatella furcifera for the parasitoid Anagrus nilaparvatae

A kairomone produced by the rice white-backed planthopper Sogatella furcifera (Horvath) for the mymarid egg parasitoid Anagrus nilaparvatae Pang et Wang was investigated. Eggs, female and male adults, nymphs, exuvia, honeydew, nymph-damaged plants and plants with S. furcifera eggs all elicited searching behavior in the parasitoid. Eggs, female adults and plants with eggs were the most attractive, while exuvia and honeydew evoked the weakest responses. The active compound(s) from S. furcifera female adults, nymphs and plants with eggs could be effectively extracted with methanol, acetone, n-hexane, ethyl ether and dichloromethane. Isolation of the active chemical(s) in three solvent extracts, the acetone and n-hexane extracts of S. furcifera female adults, and the acetone extract of S. furcifera nymphs, was accomplished by thin-layer chromatography. Only one fraction was active and had the same chemical properties in the three solvent extracts. Infra-red analysis of this fraction revealed a kind of ester with saturated and unsaturated fatty acids, which was previously found to be active in the same compound as the extracts from the nymphs and female adults of the rice brown planthopper, Nilaparvata lugens (Stål), and identified as palm oil. The results are discussed in relation to host location by A. nilaparvatae.     

Targeting the lysosome by an aminomethylated Riccardin D triggers DNA damage through cathepsin B‐mediated degradation of BRCA1

RD‐N, an aminomethylated derivative of riccardin D, is a lysosomotropic agent that can trigger lysosomal membrane permeabilization followed by cathepsin B (CTSB)‐dependent apoptosis in prostate cancer (PCa) cells, but the underlying mechanisms remain unknown. Here we show that RD‐N treatment drives CTSB translocation from the lysosomes to the nucleus where it promotes DNA damage by suppression of the breast cancer 1 protein (BRCA1). Inhibition of CTSB activity with its specific inhibitors, or by CTSB‐targeting siRNA or CTSB with enzyme‐negative domain attenuated activation of BRCA1 and DNA damage induced by RD‐N. Conversely, CTSB overexpression resulted in inhibition of BRCA1 and sensitized PCa cells to RD‐N‐induced cell death. Furthermore, RD‐N‐induced cell death was exacerbated in BRCA1‐deficient cancer cells. We also demonstrated that CTSB/BRCA1‐dependent DNA damage was critical for RD‐N, but not for etoposide, reinforcing the importance of CTSB/BRCA1 in RD‐N‐mediated cell death. In addition, RD‐N synergistically increased cell sensitivity to cisplatin, and this effect was more evidenced in BRCA1‐deficient cancer cells. This study reveals a novel molecular mechanism that RD‐N promotes CTSB‐dependent DNA damage by the suppression of BRCA1 in PCa cells, leading to the identification of a potential compound that target lysosomes for cancer treatment.