PEPped up: induction of Candida albicans virulence by bacterial cell wall fragments

In this issue, Xu et al. (2008) report that Candida albicans, a prevalent fungal pathogen, expresses virulence-related attributes in response to bacterial peptidoglycan components, muramyl dipeptides, in human serum. Conserved elements in human and fungal detection of muramyl dipeptides highlight a common ability to perceive proximal bacterial populations.     

Passing the message on: inheritance of epigenetic traits

Epigenetic modifiers play an important role in genome organization, stability and the control of gene expression. Three research groups that are exploring the transfer of epigenetic information between generations have recently published papers. Mary Alleman et al. have shown that RNA-directed chromatin changes mediate paramutation in maize, and Minoo Rassoulzadegan et al. have demonstrated that RNA also plays a role in paramutation in mice. A new aspect of epigenetic regulation has been revealed by Jean Molinier et al. - they have demonstrated that the memory of exposure to stress is transferred through several generations.     

Sex in broad daylight: turning a new leaf-fungal style

Cryptococcus spp. are potentially lethal fungal pathogens of humans and animals that are not easily communicable. In this issue of Cell Host & Microbe, Xue et al. describe sexual reproduction of Cryptococcus in association with plants and identify plant-derived mating stimulatory compounds. These results may have wide significance in explaining environmental sources of effective inoculum in human disease foci.     

Distinct, crucial roles of flavonoids during legume nodulation

RNA interference-mediated silencing of the key flavonoid and isoflavone biosynthesis enzyme, respectively, by two different research groups has provided direct genetic evidence for the essential roles that these compounds play in nodulation. Anton Wasson et al. have shown that flavonoids are essential for localized auxin transport inhibition during nodulation in the indeterminate legume Medicago truncatula. By contrast, Senthil Subramanian et al. have shown that isoflavones are essential for endogenous nod gene induction in the determinate legume soybean.     

Relationship between solubility of grifolan, a fungal 1,3-beta-D-glucan, and production of tumor necrosis factor by macrophages in vitro.

Grifolan, GRN, is a fungal antitumor beta-glucan isolated from Grifola frondosa. Various studies suggested that the underlying mechanism of the antitumor activity of GRN is strongly related to immune modulation. In the previous publication (Adachi et al., 1994; Okazaki et al., 1995), we have shown that GRN activates macrophages to produce tumor necrosis factor (TNF) in vitro. In this study, the structural unit essential to produce TNF was examined by chemical modifications of GRN. GRN suspended in distilled water was treated at 150 degrees C for up to 3 h. Addition of the resulting turbid solution to the RAW 264.7 macrophage-like cell line produced TNF, and the relative activity was diminished in relation to the heat treatment period. The fractions with a heating period longer than 15 min did not show any activity. After centrifugation of the resulting solution, significant activity was shown by precipitate fractions, suggesting that the insoluble form of GRN is important for TNF production. Interestingly, the precipitate fraction obtained from 9 min of treatment also had significant activity. In addition, admixing the soluble fraction with the particles significantly inhibited the TNF production. In contrast to these observations, the high-molecular-mass subfraction of the soluble fraction prepared by ultrafiltration produced significant amounts of TNF. Similar phenomena were shown with sodium hydroxide treatment and dimethylsulfoxide treatment. These facts strongly suggested that insoluble as well as a high molecular mass soluble form of GRN are required for TNF production by macrophages.     

Cell wall biogenesis in a double chitin synthase mutant (chsG-/chsE-) of Aspergillus fumigatus

Previous studies (Aufauvre-Brown et al., 1997; Mellado et al., 1996a,b ) have shown that only two genes of the Aspergillus fumigatus chitin synthase family, chsG and chsE, play a role in the morphogenesis of this fungal species. An A. fumigatus strain lacking both chsG (class III CHS) and chsE (class V CHS) genes was constructed by gene replacement of the chsE gene with a copy that has its conserved coding region interrupted by the hph resistance cassette in an A. fumigatus chsG- genetic background. Unexpectedly the double disruption was not lethal. The double mutant AfchsG-/chsE- strain (i) has reduced chitin synthase activity with or without trypsin stimulation, (ii) has a reduced colony radial growth rate, (iii) produces highly branched hyphae, (iv) exhibits aberrant features, such as periodic swellings along the length of the hyphae and a block in conidiation that can be partially restored by an osmotic stabilizer (v) shows alterations in the shape and germination capacity of the conidia, and (vi) has a cell wall that contains half the chitin of the parental strain and is, unexpectedly, highly enriched in alpha-(1-3) glucan.     

Functional complementarity in the arbuscular mycorrhizal symbiosis

The causes and consequences of biodiversity are central themes in ecology. Perhaps one reason for much of the current interest in biodiversity is the belief that the loss of species (by extinction) or their gain (by invasion) will significantly influence ecosystem function. Arbuscular mycorrhizal (AM) fungi are components of most terrestrial ecosystems and, while many research programs have shown that variability among species or isolates of AM fungi does occur (Giovannetti & Gianinazzi-Pearson, 1994), the basis for this variability and its consequences to the function of communities and ecosystems remains largely unexplored. Smith et al . (pp. 357–366 in this issue) now show clearly that ecologically significant functional diversity exists among AM fungal species in the regions of the soil from which they absorb phosphate, and their results suggest that such diversity may have significant ecological consequences.     

Shifted from Wnt to Hedgehog signaling pathways

Two papers in recent issue of Developmental Cell (Glise et al. 2005; Gorfinkiel et al. 2005) have shown that Shifted, a Drosophila ortholog of Wnt Inhibitory Factor (WIF), modulates the distribution of Hedgehog protein in the wing imaginal disc through a Wnt-independent mechanism.     

A new HaeIII polymorphism at the D21S13 locus

Summary DNA markers in the pericentromeric region of human chromosome 21 have shown linkage to a gene for Familial Alzheimer disease (FAD; St. George Hyslop et al. 1987). The limited informativeness of probes for the loci D21S13 and D21S16 have hindered precise mapping of the FAD locus and analysis of non-allelic heterogeneity in FAD (Schellenberg et al. 1988; St. George-Hyslop et al. 1987). We recently described a new EcoRII polymorphism at the D21S13 locus that was very informative in a large FAD pedigree (Pulst et al. 1990a, b). We now report another polymorphism for the D21S13 locus that further increases the informativeness of this locus.     

Can telomerase be put in its place?

The Cajal body is an intriguing nuclear structure present in a great variety of plant, animal, and some fungal cells. Recent work on the ribonucleoprotein enzyme telomerase has indicated an unanticipated degree of intranuclear dynamics of both its RNA and protein subunits. In this issue, Jady et al. place the Cajal body on the intranuclear traffic route of telomerase RNA (Jady et al., 2004).     

真菌发育过程中的蓝光诱导

本文对多种真菌在发育过程中受蓝光诱导的现象进行了综述。蓝光可以诱导多种真菌的形态发生和发育,包括孢子的产生和菌丝的延伸等。此外,蓝光还可引起真菌的生理和生化改变,如细胞膜对离子的通透性的变化、类胡萝卜素的合成等。真菌也存在一个蓝光信号系统,通过蓝光受体接受蓝光信号,导致了真菌的一系列形态发生和生理生化的变化。     

Prepenetration apparatus assembly precedes and predicts the colonization patterns of arbuscular mycorrhizal fungi within the root cortex of both Medicago truncatula and Daucus carota

Arbuscular mycorrhizas (AM) are widespread, ancient endosymbiotic associations that contribute significantly to soil nutrient uptake in plants. We have previously shown that initial fungal penetration of the host root is mediated via a specialized cytoplasmic assembly called the prepenetration apparatus (PPA), which directs AM hyphae through the epidermis (Genre et al., 2005). In vivo confocal microscopy studies performed on Medicago truncatula and Daucus carota, host plants with different patterns of AM colonization, now reveal that subsequent intracellular growth across the root outer cortex is also PPA dependent. On the other hand, inner root cortical colonization leading to arbuscule development involves more varied and complex PPA-related mechanisms. In particular, a striking alignment of polarized PPAs can be observed in adjacent inner cortical cells of D. carota, correlating with the intracellular root colonization strategy of this plant. Ultrastructural analysis of these PPA-containing cells reveals intense membrane trafficking coupled with nuclear enlargement and remodeling, typical features of arbusculated cells. Taken together, these findings imply that prepenetration responses are both conserved and modulated throughout the AM symbiosis as a function of the different stages of fungal accommodation and the host-specific pattern of root colonization. We propose a model for intracellular AM fungal accommodation integrating peri-arbuscular interface formation and the regulation of functional arbuscule development.     

Proposal to change the genus designation Serpula to Serpulina gen. nov. containing the species Serpulina hyodysenteriae comb. nov. and Serpulina innocens comb. nov.

The bacterial genus Serpula Stanton et al. 1991 is illegitimate due to the existence of a fungal genus Serpula Pers. ex S. F. Gray. Consequently, a new genus designation, Serpulina, is proposed for this spirochete genus. Serpula hyodysenteriae, the type species, and Serpula innocens Stanton et al. 1991, therefore, become Serpulina hyodysenteriae comb. nov. and Serpulina innocens comb. nov.     

A new EcoRI polymorphism at the D21S13 locus

Summary The D21S13 locus has shown linkage to a gene for familial Alzheimer disease (FAD) on chromosome 21 (St. George-Hyslop et al. 1987). The limited informativeness of probes for this locus have hindered precise mapping of the FAD locus and analysis of nonallelic heterogeneity in FAD (Schellenberg et al. 1988; St. George-Hyslop et al. 1987). We describe a new EcoRI polymorphism at the D21S13 locus that may be useful for the further study of FAD families.     

Induction of protection against the necrotrophic pathogens Phytophthora citrophthora and Alternaria solani in Lycopersicon esculentum Mill. by a novel synthetic glycoside combined with amines

1,2,3,4-tetra-O-acetyl-6-ethyladipate-beta- D-glucopyranose (TOGE), a glycoside derivative of adipic acid monoethyl ester and 1,2,3,4-tetra-O-acetyl-beta- D-glucopyranose, was synthesized and the resistance-inducing activity shown by TOGE-1 (TOGE plus furfurylamine) and TOGE-2 (TOGE plus 1,3-diaminepropane) was assayed. TOGE-1 and TOGE-2 protected tomato plants against two different fungal pathogens Phytophthora citrophthora and Alternaria solani. Foliar treatments at very low concentrations (2.5 mg l(-1) TOGE, 0.5 mg l(-1) amine) clearly reduced the disease incidence for both pathogens. TOGE-2 application was the most effective on intact plants as well as on detached leaves, reducing fungal growth by more than 46% with respect to control plants. On the other hand TOGE-1 treatment reduced fungal advance by 21%. These results demonstrate a high protective effect against fungal infections for both chemicals. A possible direct antimicrobial effect was discounted due to the weak activity observed in vitro against these pathogens at the low concentrations used in plants. TOGE-2 treatment clearly activates resistance against both pathogens and improves the protective effect previously shown by FGA mixture (adipic acid monoethyl ester, 1,2,3,4-tetra-O-acetyl-beta- D-glucopyranose and furfurylamine) [V. Flors et al. (2001) J Agric Food Chem 49:2569-2575]. The obtained results indicate that TOGE-1 and TOGE-2 act as resistance inducers. Although their mode of action is still unknown, pre-challenge studies have demonstrated the induction of the phenylpropanoid pathway and antioxidant activities. Both chemicals have demonstrated a beneficial effect on plant development, increasing chlorophyll and protein contents, photosynthetic rate and water-use efficiency. The improvement of plant growth and development produced by these treatments suggests crop tolerance to these chemicals, although effective formulations that are safe to humans must be developed before this technology can be used commercially.