Ss-Bi1 encodes a putative BAX inhibitor-1 protein that is required for full virulence of Sclerotinia sclerotiorum

Sclerotinia sclerotiorum is a destructive necrotrophic plant pathogen with global distribution. Although S. sclerotiorum has been studied extensively, substantial research on aspects of the pathogen's ability to cause disease is still needed. Bax inhibitor-1 protein functions as a suppressor of programmed cell death and is involved in the response to biotic and abiotic stress in animals, plants and yeast. In this study, we functionally characterized a putative Bax inhibitor-1 protein, Ss-Bi1, from S. sclerotiorum. Ss-Bi1 is predicted to contain a BAX inhibitor-1-like super family domain and shows significant homology with many BAX inhibitor-1 proteins. High expression levels of Ss-Bi1 were observed in hyphae under various stresses. Targeted silencing of Ss-Bi1 resulted in reduced virulence in host plants. Ss-Bi1 gene-silenced strains were more sensitive to heat stress and ER stress than the wild-type strain. The results suggest that Ss-Bi1 encodes a putative BAX inhibitor-1 protein that is required for full virulence of S. sclerotiorum.     

引自国际马铃薯中心的品种资源在青海对晚疫病的田间抗性鉴定

在青海省海拔2000～2500m和2500～3000m两个不同生态区域设置抗性观测圃,调查评价从国际马铃薯中心(CIP)引进的60份资源田间晚疫病抗性,资源D9在整个生育期表现出免疫症状,15个资源表现为高抗,18个资源表现抗病,同时还对晚疫病菌流行生理小种的毒性基因进行动态监测。     

Evolutionary characteristics of morbilliviruses during serial passages in vitro: Gradual attenuation of virus virulence

The genus Morbillivirus is classified into the family Paramyxoviridae, and is composed of 6 members, namely measles virus (MV), rinderpest virus (RPV), peste-des-petits-ruminants virus (PPRV), canine distemper virus (CDV), phocine distemper virus (PDV) and cetacean morbillivirus (CeMV). The MV, RPV, PPRV and CDV have been successfully attenuated through their serial passages in vitro for the production of live vaccines. It has been demonstrated that the morbilliviral virulence in animals was progressively attenuated with their consecutive passages in vitro. However, only a few reports were involved in explanation of an attenuation-related mechanism on them until many years after the establishment of a quasispecies theory. RNA virus quasispecies arise from rapid evolution of viruses with high mutation rate during genomic replication, and play an important role in gradual loss of viral virulence by serial passages. Here, we overviewed the development of live-attenuated vaccine strains against morbilliviruses by consecutive passages in vitro, and further discussed a related mechanism concerning the relationship between virulence attenuation and viral evolution.     

小麦白粉病菌越夏,越冬和春季菌源毒性结构比较

 分析了1992年和1993年不同时期采集的小麦白粉病菌越夏、越冬和春季菌源共238个菌株的生理小种、毒性基因结构和对9个推广品种的毒力频率。结果表明三种菌源在生理小种和毒性基因组成及出现频率是相似的,对9个推广品种的毒力频率均较高。这样在白粉病菌毒性和品种抗病性研究中,可以采集应用越夏和越冬菌株标样,避免了夏季高温季节保存菌株的工作;而且从毒性结构方面进一步证实白粉病菌主要以分生孢子在夏季侵染高海拔地区的自生麦苗而越夏,再逐渐扩展至秋播麦苗越冬后导致春季大田发病,病菌的子囊孢子在平原地区侵染循环上作用不大。     

Complementary host–pathogen genetic analyses of the role of fumonisins in the Zea mays–Gibberella moniliformis interaction

Zea mays often is colonized with the fungus Gibberella moniliformis, which produces fumonisin toxins. The role of fumonisins in seedling colonization and blight was studied using complementary genetic analyses of host and pathogen. Only one of two fumonisin B1 (FB1)-insensitive maize backcross lines was more resistant than the FB1-sensitive parent to seedling blight, indicating that the increase in FB1-insensitivity was not associated with an increase in resistance. FB1-producing and nonproducing isogenic fungal strains did not differ in ability to cause seedling blight, but the FB1-producing strain was more effective in systemic colonization of seedlings in reciprocal strain challenge tests. Together, these and previous results indicate that the role of fumonisins depends on complex environmental and genetic contexts in this host–pathogen interaction.     

Effects of cropping history and origin of seed potatoes on population structure of Phytophthora infestans

The effects of origin of seed potatoes and the cropping history on the phenotypic structure of Phytophthora infestans populations was studied in northern Hessia, central Germany, from 2000 to 2002. Populations originating from fields with a history of potato cropping with only short or no rotation (old fields) were compared with populations from new fields, i.e., where no potatoes had been grown for at least 30 years and seed potatoes were either imported from breeders or produced on-farm (certified). The main goal was to determine the importance of seed potato infection in the establishment of new P. infestans populations. Isolates were characterized for mating type, virulences and rep- (repetitive extragenic palindromic) PCR fingerprints. Among a total of 639 isolates sampled from 31 sites, mating types A1 and A2 co-existed in all three years in 60–92% of the sites. Over all three years, 53 pathotypes were detected in a subsample of 272 isolates. Isolates originating from the new fields had significantly higher frequencies of the virulences v1, v2, v3, v6 and v7, indicating general effects of seed introduction into a new region. Thirty-six fingerprints were detected in a subsample of 281 isolates of which 22 were unique while four occurred in all three years and in many sites. Pathogen populations from potato fields that were grown from seed tubers of geographically different origin differed significantly based on χ ² tests. While the Nei genetic distances were less than .1 among the local populations, distances to the US lineages US-1, US-6, US-7 and US-8 ranged from .22 to .47; however, the bootstrap values were not significant. Populations from old fields were more diverse and 14 of the 22 rep-PCR types occurred there among 132 isolates tested in comparison to six in the new fields (n = 140 isolates) and two among six isolates from volunteers. The results also suggest that both sexual and asexual reproduction play a role.     

多菌灵、三环唑对大丽轮枝菌微菌核、黑色素形成及致病力的影响

 在离体和活体条件下测定了多菌灵、三环唑对大丽轮枝菌的微菌核黑色素形成的影响,以及经2种杀菌剂处理产生的形态变异菌株对棉苗的致病力。结果表明:多菌灵在培养基内含量超过0.1μg/ml时,即可抑制大丽轮枝菌微菌核的形成,随着培养基内多菌灵浓度的增加,微菌核形成时间逐渐延长,形成量逐渐减少;三环唑浓度为0.5μg/ml时,可抑制微菌核的黑色素形成,微菌核从黑色变为浅红至红褐色。三环唑对微菌核黑色素形成呈可逆抑制,变色的微菌核菌落移入不含药的培养基后,大多可恢复形成黑色素。培养基内三环唑浓度的提高,也可抑制大丽轮枝菌微菌核的形成;因2种杀菌剂的抑制而丧失形成微菌核的白色菌丝体移入不含药的培养基,微菌核形成能力也不能恢复。多菌灵和三环唑经棉株吸收后均能抑制植株内大丽轮枝菌微菌核的形成,但对微菌核色素的形成未见有明显影响。2种杀菌剂处理产生的形态变异菌株的致病力与野生型菌株致病力差异不显著。     

马蹄金叶斑病发生与室内药剂毒力测定

通过对马蹄金叶斑病病原菌的分离、培养等研究,按照柯赫氏法则确定此病由胶孢炭疽菌和交链孢引起的.室内药剂毒力测定实验表明,保鲜克和百菌清对炭疽菌和交链孢菌丝的扩展蔓延作用较好,代森锌和退菌特对炭疽菌和交链孢的孢子萌发有较好的抑制作用.     

Influence of the major nitrite transporter NirC on the virulence of a Swollen Head Syndrome Avian Pathogenic E. coli (APEC) strain

Avian Pathogenic Escherichia coli (APEC) strains are extra-intestinal E. coli that infect poultry and cause diseases. Nitrite is a central branch-point in bacterial nitrogen metabolism and is used as a cytotoxin by macrophages. Unlike nitric oxide (NO), nitrite cannot diffuse across bacterial membrane cells. The NirC protein acts as a specific channel to facilitate the transport of nitrite into Salmonella and E. coli cells for nitrogen metabolism and cytoplasmic detoxification. NirC is also required for the pathogenicity of Salmonella by downregulating the production of NO by the host macrophages. Based on an in vitro microarray that revealed the overexpression of the nirC gene in APEC strain SCI-07, we constructed a nirC-deficient SCI-07 strain (ΔnirC) and evaluated its virulence potential using in vivo and in vitro assays. The final cumulative mortalities caused by mutant and wild-type (WT) were similar; while the ΔnirC caused a gradual increase in the mortality rate during the seven days recorded, the WT caused mortality up to 24 h post-infection (hpi). Counts of the ΔnirC cells in the spleen, lung and liver were higher than those of the WT after 48 hpi but similar at 24 hpi. Although similar number of ΔnirC and WT cells was observed in macrophages at 3 hpi, there was higher number of ΔnirC cells at 16 hpi. The cell adhesion ability of the ΔnirC strain was about half the WT level in the presence and absence of alpha-d-mannopyranoside. These results indicate that the nirC gene influences the pathogenicity of SCI-07 strain.     

Characterization of culture supernatant proteins from Brucella abortus and its protection effects against murine brucellosis

In this study, we characterized the secreted proteins of Brucella abortus into the enriched media under the bacterial laboratory growth condition and investigated the pathogenic importance of culture supernatant (CS) proteins to B. abortus infection. CS proteins from stationary phase were concentrated and analyzed using 2D electrophoresis. In MALDI TOF/TOF analysis, more than 27 proteins including CuZn SOD, Dps, Tat, OMPs, Adh, LivF, Tuf, SucC, GroEL and DnaK were identified. Cytotoxic effects of CS proteins were found to increase in a dose-dependent manner in RAW 264.7 cells. Upon B. abortus challenge into phagocytes, however, CS proteins pre-treated cells exhibited lower bacterial uptake and intracellular replication compared to untreated cells. Immunization with CS proteins induced a strong humoral and cell mediated immune responses and exhibited significant higher degree of protection against virulence of B. abortus infection compared to mice immunized with Brucella broth protein (BBP). Taken together, these results indicate that B. abortus secreted a number of soluble immunogenic proteins under laboratory culture condition, which can promote antibody production resulted in enhancing host defense against to subsequently bacterial infection. Moreover, further analysis of CS proteins may help to understand the pathogenic mechanism of B. abortus infection and host–pathogen interaction.