Accommodation of powdery mildew fungi in intact plant cells

Parasitic powdery mildew fungi have to overcome basic resistance and manipulate host cells to establish a haustorium as a functional feeding organ in a host epidermal cell. Currently, it is of central interest how plant factors negatively regulate basal defense or whether they even support fungal development in compatible interactions. Additionally, creation of a metabolic sink in infected cells may involve host activity. Here, we review the current progress in understanding potential fungal targets for host reprogramming and nutrient acquisition.     

Molar development in common chimpanzees (Pan troglodytes)

Numerous studies have reported on enamel and dentine development in hominoid molars, although little is known about intraspecific incremental feature variation. Furthermore, a recent histological study suggested that there is little or no time between age at chimpanzee crown completion and age at molar eruption, which is unlikely given that root growth is necessary for tooth eruption. The study presented here redefines growth standards for chimpanzee molar teeth and examines variation in incremental features. The periodicity of Retzius lines in a relatively large sample was found to be 6 or 7 days. The number of Retzius lines and cuspal enamel thickness both vary within a cusp type, among cusps, and among molars, resulting in marked variation in formation time. Daily secretion rate is consistent within analogous cuspal zones (inner, middle, and outer enamel) within and among cusp types and among molar types. Significantly increasing trends are found from inner to outer cuspal enamel (3 to 5 microns/day). Cuspal initiation and completion sequences also vary, although sequences for mandibular molar cusps are more consistent. Cusp-specific formation time ranges from approximately 2 to 3 years, increasing from M1 to M2, and often decreasing from M2 to M3. These times are intermediate between radiographic studies and a previous histological study, although both formation time within cusps and overlap between molars vary considerably. Cusp-specific (coronal) extension rates range from approximately 4 to 9 microns/day, and root extension rates in the first 5 mm of roots range from 3 to 9 microns/day. These rates are greater in M1 than in M2 or M3, and they are greater in mandibular molars than in respective maxillary molars. This significant enlargement of comparative data on nonhuman primate incremental development demonstrates that developmental variation among cusp and molar types should be considered during interpretations and comparisons of small samples of fossil hominins and hominoids.     

蝴蝶兰属植物杂交育种研究进展

对蝴蝶兰属(Phalaenopsis)植物的种质资源, 杂交育种过程中亲本的选择和某些观赏性状的遗传规律、杂交组合登录情况等进行了综述,并且对我国杂交育种中存在的问题进行了探讨,最后结合蝴蝶兰属植物遗传育种现状,就如何加快我国蝴蝶兰属植物杂交育种和新品种培育的进程提出了建议。     

烟草种间杂交亲和性

以野生烟草Nicotiana alata、N.rustica、N.repanda、N.stocktonnii与栽培烟草K326、红花大金元、Yun87、Yun97为材料,进行种间正反杂交,研究种间杂交亲和性。田间观察杂交后的坐果情况并统计坐果率,采用显微荧光染色观察授粉后花粉管在雌蕊上的生长情况,并结合杂交后代萌发检测的方法。结果表明：N.rustica、N.repanda、N.stocktonnii与栽培烟草杂交不亲和。N.rustica花粉能够穿过K326花柱,N.repanda和N.stocktonnii花粉在K326柱头上很少萌发生长。N.alata花粉可以穿过K326的花柱,并得到果实,但是萌发实验显示其种子无活力。N.alata作为母本与栽培烟草杂交不亲和。     

PATERNAL CARE: DIRECT AND INDIRECT GENETIC EFFECTS OF FATHERS ON OFFSPRING PERFORMANCE

Knowledge of how genetic effects arising from parental care influence the evolution of offspring traits comes almost exclusively from studies of maternal care. However, males provide care in some taxa, and often this care differs from females in quality or quantity. If variation in paternal care is genetically based then, like maternal care and maternal effects, paternal effects may have important consequences for the evolution of offspring traits via indirect genetic effects (IGEs). IGEs and direct–indirect genetic covariances associated with parental care can contribute substantially to total heritability and influence predictions about how traits respond to selection. It is unknown, however, if the magnitude and sign of parental effects arising from fathers are the same as those arising from mothers. We used a reciprocal cross‐fostering experiment to quantify environmental and genetic effects of paternal care on offspring performance in the burying beetle, Nicrophorus vespilloides. We found that IGEs were substantial and direct–indirect genetic covariances were negative. Combined, these patterns led to low total heritabilities for offspring performance traits. Thus, under paternal care, offspring performance traits are unlikely to evolve in response to selection, and variation in these traits will be maintained in the population despite potentially strong selection on these traits. These patterns are similar to those generated by maternal care, indicating that the genetic effects of care on offspring performance are independent of the caregiver's sex.     

In vivo protein complex topologies: sights through a cross-linking lens

Proteins are a remarkable class of molecules that exhibit wide diversity of shapes or topological features that underpin protein interactions and give rise to biological function. In addition to quantitation of abundance levels of proteins in biological systems under a variety of conditions, the field of proteome research has as a primary mission the assignment of function for proteins and if possible, illumination of factors that enable function. For many years, chemical cross-linking methods have been used to provide structural data on single purified proteins and purified protein complexes. However, these methods also offer the alluring possibility to extend capabilities to complex biological samples such as cell lysates or intact living cells where proteins may exhibit native topological features that do not exist in purified form. Recent efforts are beginning to provide glimpses of protein complexes and topologies in cells that suggest continued development will yield novel capabilities to view functional topological features of many proteins and complexes as they exist in cells, tissues, or other complex samples. This review will describe rationale, challenges, and a few success stories along the path of development of cross-linking technologies for measurement of in vivo protein interaction topologies.     

Host genetic and environmental effects on mouse intestinal microbiota

The mammalian gut harbors complex and variable microbial communities, across both host phylogenetic space and conspecific individuals. A synergy of host genetic and environmental factors shape these communities and account for their variability, but their individual contributions and the selective pressures involved are still not well understood. We employed barcoded pyrosequencing of V1-2 and V4 regions of bacterial small subunit ribosomal RNA genes to characterize the effects of host genetics and environment on cecum assemblages in 10 genetically distinct, inbred mouse strains. Eight of these strains are the foundation of the Collaborative Cross (CC), a panel of mice derived from a genetically diverse set of inbred founder strains, designed specifically for complex trait analysis. Diversity of gut microbiota was characterized by complementing phylogenetic and distance-based, sequence-clustering approaches. Significant correlations were found between the mouse strains and their gut microbiota, reflected by distinct bacterial communities. Cohabitation and litter had a reduced, although detectable effect, and the microbiota response to these factors varied by strain. We identified bacterial phylotypes that appear to be discriminative and strain-specific to each mouse line used. Cohabitation of different strains of mice revealed an interaction of host genetic and environmental factors in shaping gut bacterial consortia, in which bacterial communities became more similar but retained strain specificity. This study provides a baseline analysis of intestinal bacterial communities in the eight CC progenitor strains and will be linked to integrated host genotype, phenotype and microbiota research on the resulting CC panel.     

Strategies of attack and defense in plant–oomycete interactions, accentuated for Phytophthora parasitica Dastur (syn. P. Nicotianae Breda de Haan)

Oomycetes from the genus Phytophthora are fungus-like plant pathogens that are devastating for agriculture and natural ecosystems. Due to their particular physiological characteristics, no efficient treatments against diseases caused by these microorganisms are presently available. To develop such treatments, it appears essential to dissect the molecular mechanisms that determine the interaction between Phytophthora species and host plants. Available data are scarce, and genomic approaches were mainly developed for the two species, Phytophthora infestans and Phytophthora sojae. However, these two species are exceptions from, rather than representative species for, the genus. P. infestans is a foliar pathogen, and P. sojae infects a narrow range of host plants, while the majority of Phytophthora species are quite unselective, root-infecting pathogens. To represent this majority, Phytophthora parasitica emerges as a model for the genus, and genomic resources for analyzing its interaction with plants are developing. The aim of this review is to assemble current knowledge on cytological and molecular processes that are underlying plant–pathogen interactions involving Phytophthora species and in particular P. parasitica, and to place them into the context of a hypothetical scheme of co-evolution between the pathogen and the host.     

Patterns of protein carbonylation following oxidative stress in wild-type and<Emphasis Type="Italic"> sigB Bacillus subtilis</Emphasis> cells

Oxidative stress causes damage to nucleic acids, membrane lipids and proteins. One striking effect is the metal-catalyzed, site-specific carbonylation of proteins. In the gram-positive soil bacterium Bacillus subtilis, the PerR-dependent specific stress response and the ^B-dependent general stress response act together to make cells more resistant to oxidative stress. In this study, we analyzed the carbonylation of cytoplasmic proteins in response to hydrogen peroxide stress in B. subtilis. Furthermore, we asked whether the ^B-dependent response to oxidative stress also confers protection against protein carbonylation. To monitor the amount and specificity of protein damage, carbonyls were derivatized with 2,4-dinitrophenylhydrazine, and the resulting stable hydrazones were detected by immunoanalysis of proteins separated by one- or two-dimensional gel electrophoresis. The overall level of protein carbonylation increased strongly in cells treated with hydrogen peroxide. Several proteins, including the elongation factors EF-G, TufA and EF-Ts, were found to be highly carbonylated. Induction of the peroxide specific stress response by treatment with sub-lethal peroxide concentrations, prior to exposure to otherwise lethal levels of peroxide, markedly reduced the degree of protein carbonylation. Cells starved for glucose also showed only minor amounts of peroxide-mediated protein carbonylation compared to exponentially growing cells. We could not detect any differences between wild-type and sigB cells starved for glucose or preadapted by heat treatment with respect to the amount or specificity of protein damage incurred upon subsequent exposure to peroxide stress. However, artificial preloading with proteins that are normally induced by ^B-dependent mechanisms resulted in a lower level of protein carbonylation when cells were later subjected to oxidative stress.Communicated by W. Goebel