Botryosphaeriaceae gene machinery: Correlation between diversity and virulence

The Botryosphaeriaceae family comprises numerous fungal pathogens capable of causing economically meaningful diseases in a wide range of crops. Many of its members can live as endophytes and turn into aggressive pathogens following the onset of environmental stress events. Their ability to cause disease may rely on the production of a broad set of effectors, such as cell wall-degrading enzymes, secondary metabolites, and peptidases. Here, we conducted comparative analyses of 41 genomes representing six Botryosphaeriaceae genera to provide insights into the genetic features linked to pathogenicity and virulence. We show that these Botryosphaeriaceae genomes possess a large diversity of carbohydrate-active enzymes (CAZymes; 128 families) and peptidases (45 families). Botryosphaeria, Neofusicoccum, and Lasiodiplodia presented the highest number of genes encoding CAZymes involved in the degradation of the plant cell wall components. The genus Botryosphaeria also exhibited the highest abundance of secreted CAZymes and peptidases. Generally, the secondary metabolites gene cluster profile was consistent in the Botryosphaeriaceae family, except for Diplodia and Neoscytalidium. At the strain level, Neofusicoccum parvum NpBt67 stood out among all the Botryosphaeriaceae genomes, presenting a higher number of secretome constituents. In contrast, the Diplodia strains showed the lowest richness of the pathogenicity- and virulence-related genes, which may correlate with their low virulence reported in previous studies. Overall, these results contribute to a better understanding of the mechanisms underlying pathogenicity and virulence in remarkable Botryosphaeriaceae species. Our results also support that Botryosphaeriaceae species could be used as an interesting biotechnological tool for lignocellulose fractionation and bioeconomy.     

Functional molecular aspects of the NADH dehydrogenases of plant mitochondria

There are multiple routes of NAD(P)H oxidation associated with the inner membrane of plant mitochondria. These are the phosphorylating NADH dehydrogenase, otherwise known as Complex I, and at least four other nonphosphorylating NAD(P)H dehydrogenases. Complex I has been isolated from beetroot, broad bean, and potato mitochondria. It has at least 32 polypeptides associated with it, contains FMN as its prosthetic group, and the purified enzyme is sensitive to inhibition by rotenone. In terms of subunit complexity it appears similar to the mammalian and fungal enzymes. Some polypeptides display antigenic similarity to subunits fromNeurospora crassa but little cross-reactivity to antisera raised against some beef heart complex I subunits. Plant complex I contains eight mitochondrial encoded subunits with the remainder being nuclear-encoded. Two of these mitochondrial-encoded subunits, nad7 and nad9, show homology to corresponding nuclear-encoded subunits inNeurospora crassa (49 and 30 kDa, respectively) and beef heart CI (49 and 31 kDa, respectively), suggesting a marked difference between the assembly of CI from plants and the fungal and mammalian enzymes. As well as complex I, plant mitochondria contain several type-II NAD(P)H dehydrogenases which mediate rotenone-insensitive oxidation of cytosolic and matrix NADH. We have isolated three of these dehydrogenases from beetroot mitochondria which are similar to enzymes isolated from potato mitochondria. Two of these enzymes are single polypeptides (32 and 55 kDa) and appear similar to those found in maize mitochondria, which have been localized to the outside of the inner membrane. The third enzyme appears to be a dimer comprised of two identical 43-kDa subunits. It is this enzyme that we believe contributes to rotenone-insensitive oxidation of matrix NADH. In addition to this type-II dehydrogenases, several observations suggest the presence of a smaller form of CI present in plant mitochondria which is insensitive to rotenone inhibition. We propose that this represents the peripheral arm of CI in plant mitochondria and may participate in nonphosphorylating matrix NADH oxidation.     

A survey of black dot and other fungal tuber blemishing diseases in British potato crops at harvest

Black dot and other fungal blemishing diseases were assessed on tubers from crops in eastern England in 1987 and 1988, and in 1989 and 1990 from crops throughout Great Britain. Black dot was found on tubers in crops from all areas of the country, and was most common in those from eastern and southern England. The disease was scarce on most Scottish crops, but occasionally some were severely affected. In 1988 there was no consistent relationship between the amounts of disease on the seed and subsequent ware crop. On average, the disease was more prevalent in irrigated crops and where the interval between successive potato crops was short. In 1990 treating seed tubers with fungicide had no effect on subsequent levels of disease. Few crops were unaffected by silver scurf, and it was most common in crops from southern and eastern England. In the national survey common scab was the most prevalent disease, black scurf was less common and skin spot and powdery scab uncommon except in some Scottish crops.     

Comparative Physiology and Behaviour of the Mycoparasites Pythium acanthophoron, P. oligandrum and P. mycoparasiticum

Pythium acanthophoron (two isolates) was as aggressive as P. oligandrum in hyphal interactions with Fusarium oxysporum on water agar films. It caused rapid post-contact lysis or cytoplasmic coagulation of the host, and often branched and penetrated the host at contact points. P. acanthophoron grew across a range of fungi on pre-colonized agar plates; the range was narrower than for P. oligandrum but broader than for P. mycoparasiticum. In chemically defined liquid media, P. acanthophoron was unique among the six known mycoparasitic Pythium spp. in requiring organic nitrogen but not thiamine. It also grew on mannitol as the sole carbon source in the presence of calcium or sterols or both. However, individual isolates of the three mycoparasitic species showed different responses to calcium and the sterols ergosterol, cholesterol and beta-sitosterol when grown on mannitol. All three mycoparasites required components of molasses, carrot extract or sunflower seed extract to produce oogonia in culture; they formed few oogonia on potato extract, with or without dextrose, even when supplied with sterols. The three mycoparasites were less tolerant of high NaCl levels in culture than were three phytopathogens (P. aphanidermatum, P. ultimum, P. graminicola), in contrast to a previous report for P. oligandrum and P. ultimum. These in vitro studies suggest that P. acanthophoron has potential for use as a biocontrol agent instead of, or in addition to, P. oligandrum.     

Relationship of alpha MSH-specific neurons to the arcuate opiocortin neuronal system as determined by dual antigen immunocytochemical procedures

The cross-immunoreactivity, topography, and fiber projections of the alpha MSH-immunoreactive specific neurons in the forebrain of the rat appear to be distinctly different from that of the neurons in the hypothalamic arcuate opiocortin system. The cell bodies, immunoreactive only to -MSH, have a specific pattern of distribution in the dorsal and lateral hypothalamic regions from the level of the retrochiasmatic region to the premammillary area of the posterior hypothalamus. Immunoreactive fibers of these cells appear to extend into regions of the cerebral cortex and hippocampus. An antomical relationship between the immunostained fibers and/or terminals of the arcuate opiocortin pool of neurons and the -MSH-immunoreactive perikarya is described utilizing the ABC (Avidin-Biotin-Peroxidase Complex) and ABC-GO (Glucose Oxidase) or glucose oxidase-antiglucose oxidase complex methods of immunocytochemistry in which two tissue antigens with contrasting colors are demonstrated in the same tissue section.     

Age-specific survivorship analysis ofHeliothis spp. Populations on cotton

Population dynamics of Heliothis virescens (F.) and Heliothis zea (Boddie ) (Lepidoptera: Noctuidae) eggs and larvae were studied for two years in a small plot of cotton, Gossypium hirsutum (L.). Due to morphological and ecological similarities, the pooled Heliothis population was considered for most of the analyses. Two generations of Heliothis eggs and larvae were completed during each year. Stage recruitment was estimated for the eggs and larval instars 2–6, and recruitment variances were estimated by a Monte Carlo method. A modified form of the Weibull distribution was developed and used as a model to characterize survivorship curves for each of the four Heliothis generations. A Type I survivorship curve (mortality rate increasing with age) was inferred for both Generation 1 (early season) data sets, whereas a Type II survivorship curve (mortality rate constant and thus independent of age) was inferred for both Generation 2 (late season) data sets. The shapes of the survivorship curves for the individual H. virescens and H. zea populations were inferred to be the same as those for the pooled populations. Analysis of the contributions of various factors to Heliothis stage-specific mortality indicated that natural enemies (predators and parasites) and the availability of food for larvae were responsible for between-generation differences in survivorship patterns.     

急性病毒性肝炎的发病率慢性肝炎患病率和肝病死亡率的研究

1984～1987年,在黑龙江、河北、河南、湖南、上海五个省市城乡10.08855人口中进行急性肝炎发病率、慢性肝炎患病率、与病毒性肝炎有关的肝病死亡率的研究。急性肝炎标化发病率为152.19/10万,主要发生在20～50岁组人群;因无甲肝暴发流行,除上海外各点季节发病率分布均衡。慢性肝炎标化患病率为158.25/10万(诊断标准为6个月前有明确急性肝炎病史,现有明显的临床症状或体征,肝功能异常,故实际慢肝患病率要高于此数字);与病毒性肝炎有关的肝病死亡(包括肝癌)标化率为22.65/10万,其中肝病为 13.14/10万。男性死亡率显著高于女性。     

On the evolution of the bacterial major sigma factors

Summary The existence of internal sequence homologies between the N-terminal halves of the gram-negative bacterial major sigma factors and their C-terminal halves, which correspond to minor factors, is reported. In the case of Escherichia-Salmonella sigma-70, an apparent homology was even found between the C-terminal helix-turn-helix DNA-binding motif and the corresponding region of the peptide N half, which, however, is not directly engaged in promoter recognition. It is proposed that major sigma factors may have originated by duplication and fusion of a DNA unit related to the ancestral gene for the whole sigma family. Coevolution of major sigma structures and complex promoters is suggested.     

Integral equation models for endemic infectious diseases

Summary Endemic infectious diseases for which infection confers permanent immunity are described by a system of nonlinear Volterra integral equations of convolution type. These constant-parameter models include vital dynamics (births and deaths), immunization and distributed infectious period. The models are shown to be well posed, the threshold criteria are determined and the asymptotic behavior is analysed. It is concluded that distributed delays do not change the thresholds and the asymptotic behaviors of the models.This work was partially supported by NIH Grant AI 13233.     

Inborn errors of cobalamin metabolism: Effect of cobalamin supplementation in culture on methylmalonyl CoA mutase activity in normal and mutant human fibroblasts

We have examined the effect of addition of hydroxocobalamin to growth medium on the activity of the adenosylcobalamin-requiring enzyme methylmalonyl CoA mutase in normal human fibroblasts and in mutant human fibroblasts derived from patients with inherited methylmalonicacidemia. The mutant cell lines were assigned to four distinct genetic complementation groups (cbl A, cbl B, cbl C, and cbl D), each deficient in some step in the synthesis of adenosylcobalamin from hydroxocobalamin. After control cells were grown in cobalamin-supplemented medium, mutase holoenzyme activity increased markedly in a time- and concentration-dependent fashion. Growth in cobalamin-supplemented medium had no effect on mutase activity in some mutant lines belonging to the cbl B group, while activity increased severalfold in other cbl B mutants and in all cbl A, cbl C, and cbl D mutants examined, although mutase activity was still <10% of control. Comparison of mutase holoenzyme activity and total propionate pathway activity suggests that enhancement of mutase activity in mutant cells after cobalamin supplementation to values 5–10% of control may be sufficient to overcome the inherited metabolic block and to restore total pathway activity to normal.This work was supported in part by a research grant from the National Institutes of Health (AM 12579). H. F. W. is a recipient of a traineeship from the National Institutes of Health (T01-GM02299).