Guanosine-specific single-stranded ribonuclease effectors of a phytopathogenic fungus potentiate host immune responses

Plants activate immunity upon recognition of pathogen-associated molecular patterns. Although phytopathogens have evolved a set of effector proteins to counteract plant immunity, some effectors are perceived by hosts and induce immune responses. Here, we show that two secreted ribonuclease effectors, SRN1 and SRN2, encoded in a phytopathogenic fungus, Colletotrichum orbiculare, induce cell death in a signal peptide- and catalytic residue-dependent manner, when transiently expressed in Nicotiana benthamiana. The pervasive presence of SRN genes across Colletotrichum species suggested the conserved roles. Using a transient gene expression system in cucumber (Cucumis sativus), an original host of C. orbiculare, we show that SRN1 and SRN2 potentiate host pattern-triggered immunity responses. Consistent with this, C. orbiculare SRN1 and SRN2 deletion mutants exhibited increased virulence on the host. In vitro analysis revealed that SRN1 specifically cleaves single-stranded RNAs at guanosine, leaving a 3'-end phosphate. Importantly, the potentiation of C. sativus responses by SRN1 and SRN2, present in the apoplast, depends on ribonuclease catalytic residues. We propose that the pathogen-derived apoplastic guanosine-specific single-stranded endoribonucleases lead to immunity potentiation in plants.

Efficient multiple gene knockout in Colletotrichum higginsianum via CRISPR/Cas9 ribonucleoprotein and URA3-based marker recycling

Colletotrichum higginsianum is a hemibiotrophic pathogen that causes anthracnose disease on crucifer hosts, including Arabidopsis thaliana. Despite the availability of genomic and transcriptomic information and the ability to transform both organisms, identifying C. higginsianum genes involved in virulence has been challenging due to recalcitrance to gene targeting and redundancy of virulence factors. To overcome these obstacles, we developed an efficient method for multiple gene disruption in C. higginsianum by combining CRISPR/Cas9 and a URA3-based marker recycling system. Our method significantly increased the efficiency of gene knockout via homologous recombination by introducing genomic DNA double-strand breaks. We demonstrated the applicability of the URA3-based marker recycling system for multiple gene targeting in the same strain. Using our technology, we successfully targeted two melanin biosynthesis genes, SCD1 and PKS1, which resulted in deficiency in melanization and loss of pathogenicity in the mutants. Our findings demonstrate the effectiveness of our methods in analysing virulence factors in C. higginsianum, thus accelerating research on plant-fungus interactions.

A parasitic fungus employs mutated eIF4A to survive on rocaglate-synthesizing Aglaia plants

Plants often generate secondary metabolites as defense mechanisms against parasites. Although some fungi may potentially overcome the barrier presented by antimicrobial compounds, only a limited number of examples and molecular mechanisms of resistance have been reported. Here, we found an Aglaia plant-parasitizing fungus that overcomes the toxicity of rocaglates, which are translation inhibitors synthesized by the plant, through an amino acid substitution in a eukaryotic translation initiation factor (eIF). De novo transcriptome assembly revealed that the fungus belongs to the Ophiocordyceps genus and that its eIF4A, a molecular target of rocaglates, harbors an amino acid substitution critical for rocaglate binding. Ribosome profiling harnessing a cucumber-infecting fungus, Colletotrichum orbiculare, demonstrated that the translational inhibitory effects of rocaglates were largely attenuated by the mutation found in the Aglaia parasite. The engineered C. orbiculare showed a survival advantage on cucumber plants with rocaglates. Our study exemplifies a plant-fungus tug-of-war centered on secondary metabolites produced by host plants.

The Conserved Colletotrichum spp. Effector Candidate CEC3 Induces Nuclear Expansion and Cell Death in Plants

Plant pathogens secrete proteins, known as effectors, that promote infection by manipulating host cells. Members of the phytopathogenic fungal genus Colletotrichum collectively have a broad host range and generally adopt a hemibiotrophic lifestyle that includes an initial biotrophic phase and a later necrotrophic phase. We hypothesized that Colletotrichum fungi use a set of conserved effectors during infection to support the two phases of their hemibiotrophic lifestyle. This study aimed to examine this hypothesis by identifying and characterizing conserved effectors among Colletotrichum fungi. Comparative genomic analyses using genomes of ascomycete fungi with different lifestyles identified seven effector candidates that are conserved across the genus Colletotrichum. Transient expression assays showed that one of these putative conserved effectors, CEC3, induces nuclear expansion and cell death in Nicotiana benthamiana, suggesting that CEC3 is involved in promoting host cell death during infection. Nuclear expansion and cell death induction were commonly observed in CEC3 homologs from four different Colletotrichum species that vary in host specificity. Thus, CEC3 proteins could represent a novel class of core effectors with functional conservation in the genus Colletotrichum.

Comparative transient expression analyses on two conserved effectors of Colletotrichum orbiculare reveal their distinct cell death-inducing activities between Nicotiana benthamiana and melon

Colletotrichum orbiculare infects cucurbits, such as cucumber and melon (Cucumis melo), as well as the model Solanaceae plant Nicotiana benthamiana, by secreting an arsenal of effectors that suppress the immunity of these distinct plants. Two conserved effectors of C. orbiculare, called NLP1 and NIS1, induce cell death responses in N. benthamiana, but it is unclear whether they exhibit the same activity in Cucurbitaceae plants. In this study, we established a new Agrobacterium-mediated transient expression system to investigate the cell death-inducing activity of NLP1 and NIS1 in melon. NLP1 strongly induced cell death in melon but, in contrast to the effects seen in N. benthamiana, mutations either in the heptapeptide motif or in the putative glycosylinositol phosphorylceramide-binding site did not cancel its cell death-inducing activity in melon. Furthermore, NLP1 lacking the signal peptide caused cell death in melon but not in N. benthamiana. Study of the transient expression of NIS1 also revealed that, unlike in N. benthamiana, NIS1 did not induce cell death in melon. In contrast, NIS1 suppressed flg22-induced reactive oxygen species generation in melon, as seen in N. benthamiana. These findings indicate distinct cell death-inducing activities of NLP1 and NIS1 in these two plant species that C. orbiculare infects.

Telomeres and a repeat-rich chromosome encode effector gene clusters in plant pathogenic Colletotrichum fungi

Members of the Colletotrichum gloeosporioides species complex are causal agents of anthracnose in many commercially important plants. Closely related strains have different levels of pathogenicity on hosts despite their close phylogenetic relationship. To gain insight into the genetics underlying these differences, we generated and annotated whole-genome assemblies of multiple isolates of C. fructicola (Cf) and C. siamense (Cs), as well as three previously unsequenced species, C. aenigma (Ca), C. tropicale and C. viniferum with different pathogenicity on strawberry. Based on comparative genomics, we identified accessory regions with a high degree of conservation in strawberry-pathogenic Cf, Cs and Ca strains. These regions encode homologs of pathogenicity-related genes known as effectors, organized in syntenic gene clusters, with copy number variations in different strains of Cf, Cs and Ca. Analysis of highly contiguous assemblies of Cf, Cs and Ca revealed the association of related accessory effector gene clusters with telomeres and repeat-rich chromosomes and provided evidence of exchange between these two genomic compartments. In addition, expression analysis indicated that orthologues in syntenic gene clusters showed a tendency for correlated gene expression during infection. These data provide insight into mechanisms by which Colletotrichum genomes evolve, acquire and organize effectors.

Genomic Plasticity Mediated by Transposable Elements in the Plant Pathogenic Fungus Colletotrichum higginsianum

Phytopathogen genomes are under constant pressure to change, as pathogens are locked in an evolutionary arms race with their hosts, where pathogens evolve effector genes to manipulate their hosts, whereas the hosts evolve immune components to recognize the products of these genes. Colletotrichum higginsianum (Ch), a fungal pathogen with no known sexual morph, infects Brassicaceae plants including Arabidopsis thaliana. Previous studies revealed that Ch differs in its virulence toward various Arabidopsis thaliana ecotypes, indicating the existence of coevolutionary selective pressures. However, between-strain genomic variations in Ch have not been studied. Here, we sequenced and assembled the genome of a Ch strain, resulting in a highly contiguous genome assembly, which was compared with the chromosome-level genome assembly of another strain to identify genomic variations between strains. We found that the two closely related strains vary in terms of large-scale rearrangements, the existence of strain-specific regions, and effector candidate gene sets and that these variations are frequently associated with transposable elements (TEs). Ch has a compartmentalized genome consisting of gene-sparse, TE-dense regions with more effector candidate genes and gene-dense, TE-sparse regions harboring conserved genes. Additionally, analysis of the conservation patterns and syntenic regions of effector candidate genes indicated that the two strains vary in their effector candidate gene sets because of de novo evolution, horizontal gene transfer, or gene loss after divergence. Our results reveal mechanisms for generating genomic diversity in this asexual pathogen, which are important for understanding its adaption to hosts.

Establishment of a selection marker recycling system for sequential transformation of the plant-pathogenic fungus Colletotrichum orbiculare

Genome sequencing of pathogenic fungi has revealed the presence of various effectors that aid pathogen invasion by the manipulation of plant immunity. Effectors are often individually dispensable because of duplication and functional redundancy as a result of the arms race between host plants and pathogens. To study effectors that have functional redundancy, multiple gene disruption is often required. However, the number of selection markers that can be used for gene targeting is limited. Here, we established a marker recycling system that allows the use of the same selection marker in successive transformations in the model fungal pathogen Colletotrichum orbiculare, a causal agent of anthracnose disease in plants belonging to the Cucurbitaceae. We identified two C. orbiculare homologues of yeast URA3/pyrG, designated as URA3A and URA3B, which can be used as selection markers on medium with no uridine. The gene can then be removed from the genome via homologous recombination when the fungus is grown in the presence of 5-fluoroorotic acid (5-FOA), a chemical that is converted into a toxin by URA3 activity. The ura3a/b double mutants showed auxotrophy for uridine and insensitivity to 5-FOA. Using the ura3a/b mutants, transformation with the URA3B marker and its removal were successfully applied to disrupt the virulence-related gene, PKS1. The pks1 mutants showed a reduction in virulence, demonstrating that the method can be used to study virulence-related genes in C. orbiculare. The establishment of a URA3-based marker recycling system in plant-pathogenic fungi enables the genetic analysis of multiple genes that have redundant functions, including effector genes.

Interconnections between mRNA degradation and RDR-dependent siRNA production in mRNA turnover in plants

Accumulation of an mRNA species is determined by the balance between the synthesis and the degradation of the mRNA. Individual mRNA molecules are selectively and actively degraded through RNA degradation pathways, which include 5'-3' mRNA degradation pathway, 3'-5' mRNA degradation pathway, and RNA-dependent RNA polymerase-mediated mRNA degradation pathway. Recent studies have revealed that these RNA degradation pathways compete with each other in mRNA turnover in plants and that plants have a hidden layer of non-coding small-interfering RNA production from a set of mRNAs. In this review, we summarize the current information about plant mRNA degradation pathways in mRNA turnover and discuss the potential roles of a novel class of the endogenous siRNAs derived from plant mRNAs.

Genus-Wide Comparative Genome Analyses of Colletotrichum Species Reveal Specific Gene Family Losses and Gains during Adaptation to Specific Infection Lifestyles

Members from Colletotrichum genus adopt a diverse range of lifestyles during infection of plants and represent a group of agriculturally devastating pathogens. In this study, we present the draft genome of Colletotrichum incanum from the spaethianum clade of Colletotrichum and the comparative analyses with five other Colletotrichum species from distinct lineages. We show that the C. incanum strain, originally isolated from Japanese daikon radish, is able to infect both eudicot plants, such as certain ecotypes of the eudicot Arabidopsis, and monocot plants, such as lily. Being closely related to Colletotrichum species both in the graminicola clade, whose members are restricted strictly to monocot hosts, and to the destructivum clade, whose members are mostly associated with dicot infections, C. incanum provides an interesting model system for comparative genomics to study how fungal pathogens adapt to monocot and dicot hosts. Genus-wide comparative genome analyses reveal that Colletotrichum species have tailored profiles of their carbohydrate-degrading enzymes according to their infection lifestyles. In addition, we show evidence that positive selection acting on secreted and nuclear localized proteins that are highly conserved may be important in adaptation to specific hosts or ecological niches.

Arabidopsis AtRRP44A is the functional homolog of Rrp44/Dis3, an exosome component, is essential for viability and is required for RNA processing and degradation

The RNA exosome is a multi-subunit complex that is responsible for 3ʹ to 5ʹ degradation and processing of cellular RNA. Rrp44/Dis3 is the catalytic center of the exosome in yeast and humans. However, the role of Rrp44/Dis3 homologs in plants is still unidentified. Here, we show that Arabidopsis AtRRP44A is the functional homolog of Rrp44/Dis3, is essential for plant viability and is required for RNA processing and degradation. We characterized AtRRP44A and AtRRP44B/SOV, two predicted Arabidopsis Rrp44/Dis3 homologs. AtRRP44A could functionally replace S. cerevisiae Rrp44/Dis3, but AtRRP44B/SOV could not. rrp44a knock-down mutants showed typical phenotypes of exosome function deficiency, 5.8S rRNA 3ʹ extension and rRNA maturation by-product over-accumulation, but rrp44b mutants did not. Conversely, AtRRP44B/SOV mutants showed elevated levels of a selected mRNA, on which rrp44a did not have detectable effects. Although T-DNA insertion mutants of AtRRP44B/SOV had no obvious phenotype, those of AtRRP44A showed defects in female gametophyte development and early embryogenesis. These results indicate that AtRRP44A and AtRRP44B/SOV have independent roles for RNA turnover in plants.

The role of decapping proteins in the miRNA accumulation in Arabidopsis thaliana

Decapping 1 (DCP1), Decapping 2 (DCP2) and VARICOSE (VCS) are components of the decapping complex that removes the 7-methyl-guanosine 5'-diphosphate from the 5' end of mRNAs. In animals, the decapping proteins are involved in miRNA-mediated gene silencing, whereas in plants the roles of the decapping proteins in the miRNA pathway are not well understood. Here we demonstrated that the accumulation of miRNAs decreased in dcp1, dcp2 and vcs mutants, indicating that DCP1, DCP2 and VCS are important for the miRNA pathway in Arabidopsis thaliana. The primary miRNAs (pri-miRNAs) did not increase and miRNA biogenesis components did not decrease in these mutants, suggesting that the miRNA decrease in decapping mutants is not due to the defect of pri-miRNA processing. We showed that the accumulation of miRNA targets increased concomitantly with the decrease of miRNA in the decapping mutants. Our results suggested that the seedling lethal phenotypes in the dcp1, dcp2 and vcs mutants are caused not only by the defect in decapping, but also by the disruption of miRNA-mediated gene regulation.

SGS3 and RDR6 interact and colocalize in cytoplasmic SGS3/RDR6-bodies

Suppressor of gene silencing 3 (SGS3) is involved in RNA-dependent RNA polymerase 6 (RDR6)-dependent small-interfering RNA (siRNA) pathways in Arabidopsis. However, the roles of SGS3 in those pathways are unclear. Here, we show that SGS3 interacts and colocalizes with RDR6 in cytoplasmic granules. Interestingly, the granules containing SGS3 and RDR6 (named SGS3/RDR6-bodies) were distinct from the processing bodies where mRNAs are decayed and/or stored. Microscopic analyses and complementation experiments using SGS3-deletion mutants suggested that proper localization of SGS3 is important for its function. These results provide novel insights into RDR6-dependent siRNA formation in plants.

Correlation between messenger RNA expression of cytochrome P450 aromatase and its enzyme activity during oocyte development in the red seabream (Pagrus major)

In teleosts, estradiol-17beta (E2) is an important hormone responsible for oocyte development. To elucidate the molecular mechanisms underlying E2 biosynthesis, we characterized the structure of red seabream (Pagrus major) cytochrome P450 aromatase (P450(arom)) that is directly involved in E2 biosynthesis and found changes in mRNA levels of P450(arom) during oocyte development induced by implantation of gonadotropin-releasing hormone analogue. A cDNA clone encoding P450(arom) is 1779 base pairs in length and encodes a protein of 519 amino acids in length, with a calculated molecular weight of 58.9 kDa. Northern blot analysis showed that P450(arom) mRNA levels increased gradually from Day 8, when oocytes reached the secondary yolk globule stage, and were maintained at high levels at the day of spawning (Day 15). The P450(arom) mRNA levels increased in association with an increase of the gonadosomatic index (gonad weight/body weight x 100%), serum E2, and P450(arom) enzyme activity (in vitro conversion of testosterone to E2 in the ovarian fragments). Furthermore, an increase in mRNA levels of the LHbeta, but not FSHbeta, correlated with increased P450(arom) mRNA levels during the course of ovarian development. In addition, the levels of P450(arom) mRNA increased in isolated ovarian follicles during the course of vitellogenic oocyte growth and became undetectable in follicles at the migratory nucleus and the mature stages. These findings, together with those of the previous studies, suggest that LH, not FSH, may regulate E2 biosynthesis via increased levels of P450(arom) mRNA during oocyte development of red seabream.

["Wish to die" and "right to die" in a case of schizophrenia]

Protection of life had long been the ultimate goal of medicine. Recently, patient's subjective judgement and self-determination also became another alternative principle. The situation is the same in psychiatry. Now, most patients with "wish to die" live in community, unless they show strong and urgent suicidal attempt. Meanwhile, "right to die" based on patient's self-determination has been established in the terminal state of cancer. Based on the same logical formulation, the "right to kill oneself" for patients with "intolerable psychological pain", is also asserted. Suicide as a right is now an impending agenda in psychiatry. A case of schizophrenia, who had killed her mother and who had "wish to die", was presented and discussed here. Conclusions were as follows: 1) "Wish to die" was psychologically interpreted as "denial of wish to live". At least, this meant that "wish to die" was unable to be a clear and convincing evidence that "real will" to die actually existed. 2) Nevertheless, the therapist who was overwhelmed by the patient's "wish to die", felt that it was a patient's real will to die. 3) "Wish to die" was not a self-determination to die, but rather a patient's inquiry into the quality of therapy, if the therapist was able to tolerate the wish. 4) If everyone is supposed to have privacy that none can ever intrude, this right should be the one only for limiting excessive intervention of medicine, but not for helping suicide. 5) How to verbalize patient's "wish to live" hidden deeply at the very core of "wish to die" and how to support the patient's "wish to live", had a crucial importance in clinical practice of suicidal patients for therapists to confront "wish to die" together with the patient. 6) In general, it was discussed that the concept of "right to die" in suicide and in terminal states, had to be constructed in some different way.

Heterosexual activity as a risk factor for the transmission of hepatitis C virus

Hepatitis C virus (HCV), the major causative agent of non-A, non-B hepatitis, is transmitted by parenteral exposure. Transmission by sexual activity, however, is controversial. Possible behavioral risk factors for HCV infection were studied retrospectively among imprisoned men (n = 201, mean age: 45 years [S.D. 13]) who visited a health service center at a Japanese correctional facility for medical examination. Seropositivity of anti-HCV antibody was disproportionately high (49.8%) in comparison with volunteer blood donors. Among possible risk factors significant on univariate analysis, intravenous drug abuse and Tama-Ire, a Japanese custom of sexual behavior that suggests frequent, aggressive or promiscuous heterosexual activity, proved to be independent risk factors for HCV infection (odds ratio = 7.39, 95% CI = 3.41 - 16.05, P < 0.0001; odds ratio = 3.16, 95% CI = 1.16 - 8.64, P = 0.026, respectively) as shown by logistic regression analysis. The data suggest that HCV may be transmitted by sexual activity.

The patient as "subject" and capacity to give informed consent

In line with Western countries, the idea of "capacity assessment" to determine a person's course of treatment is being introduced to Japanese psychiatry. Herein, some problems associated with the informed consent of mental patients are discussed, and a typical case is presented. The author points out that, when involuntary treatment is necessary, the clinician must consider, 1) the self as a "subject" of the incapable, 2) the dissociation between a subject and a choice, 3) the nature of choice in life, 4) contextual assessment of mental intervention in the patient's life situation. Neglecting these issues will lead to inhumane medical practice in psychiatry.

Attitude change towards mental illness during nursing education--a cross-cultural study of student nurses in Korea, Republic of China and Japan

This is an initial report of a cooperative project by colleagues in Korea, the Republic of China (Taiwan) and Japan, involving the measuring of attitudes toward mental illness. The discussion mainly revolves around the influence of mental health education in nursing on attitudes towards mental illness. The subjects' attitudes were assessed by Wig's profiles. The attitudes of freshmen who had just entered nursing schools and seniors who had already finished clinical training in psychiatry were compared to measure the attitude change during the course of nursing education, if any. Non-medical students served as a control group. As a result, a seemingly "negative and pessimistic" attitude was demonstrated in the senior student nurses. The findings are examined and discussed.

Lobar intracerebral hemorrhage. A clinical, radiographic, and pathological study of 29 consecutive operated cases with negative angiography

The authors operated consecutively on 50 patients with lobar intracerebral hemorrhage during a prospectively designed study period from January, 1986, to March, 1990. They investigated the correlations between the underlying causes and the clinicoradiographic features in 29 patients who showed no angiographic vascular abnormalities, in order to elucidate the operative indication for such cases. Patients with ruptured saccular aneurysm or trauma were not included in this study. There were 15 males and 14 females, ranging in age from 7 to 76 years (mean 52.4 years). Histological diagnoses of the surgical specimens were as follows: vascular malformation in nine cases (arteriovenous malformation (AVM) in six and cavernous malformation in three), microaneurysm in 11, cerebral amyloid angiopathy in six, and brain tumor in two; in the remaining case the cause was not verified histologically. The underlying cause was determined in 96.5% of cases. The mean patient age was lowest in the cavernous malformation group (27.0 years), followed by the AVM (45.8 years), microaneurysm (59.8 years), and cerebral amyloid angiopathy (70.0 years) groups. Four patients with vascular malformation (three AVM's and one cavernous malformation) had previous episodes of bleeding at the same site, whereas none of those with microaneurysms or cerebral amyloid angiopathy had such episodes. On computerized tomography (CT) scans, the round to oval hematoma was related to the presence of an AVM or cavernous malformation in contrast to microaneurysms and cerebral amyloid angiopathy. Upon infusion of contrast material, variable enhancement was seen in five (two AVM's and three cavernous malformations) of the nine vascular malformations while no enhancement was noted in any patient with microaneurysm or cerebral amyloid angiopathy at the acute stage. Subarachnoid extension of the hematoma was associated with cerebral amyloid angiopathy significantly more frequently than with AVM's (p less than 0.05) and microaneurysms (p less than 0.01). The results suggest that clinicoradiographic pictures in cases with negative angiography are quite different among the three major pathological categories; namely, vascular malformation (AVM and cavernous malformation), microaneurysm, and cerebral amyloid angiopathy. It is suggested that the underlying etiology of a given lobar intracerebral hemorrhage with negative angiography may be predicted by a combination of patient age, history of previous bleeding at the same site, hematoma shape, and subarachnoid extension of the hematoma on CT scans. Based upon these findings, the authors discuss operative indications for such cases.

How depressing life is--life-long morbidity risk for depressive disorder in the general population

We present estimates of lifetime risk and of cumulative risk up to each age for depressive disorder for the population of an inner city area (Camberwell, SE London). Estimates are based on an incidence study for the year 1976 which drew from the records of a case register. The estimates of lifetime risk obtained, 12% for men and 20% for women, are similar to those previously published in the literature. Inception risk by age and risks for in-patient treatment are also presented for men and women. The method of calculation is discussed and we show how to obtain an upper limit for the effect of the increased mortality associated with the disorder. We noted an apparent decline over the 'seventies' in inception rates for depression, and we consider the comparability of our statistics with risks calculated using complete psychiatric history data.

The Study of Depressive Disorders Using the PSE-ID-CATEGO System

The PSE-CATEGO-ID system and its approach to the sub-classification of depression is described. The principle of sub-classification partly corresponds to the empirical relationships between symptoms on affective disorder. Comparison of CATEGO and DSM III demonstrates that major differences of classification can arise because of differences of the classificatory algorithm even though similar lists of symptoms are used. Empirical studies of the PSE-CATEGORO-ID system are described and their importance in providing evidence for a rational choice between classificatory system is emphasised.