Genotype-specific interactions and the trade-off between host and parasite fitness

Background  

Evolution of parasite traits is inextricably linked to their hosts. For instance one common definition of parasite virulence is the reduction in host fitness due to infection. Thus, traits of infection must be viewed in both protagonists and may be under shared genetic and physiological control. We investigated these questions on the oomycete Hyaloperonospora arabidopsis (= parasitica), a natural pathogen of the Brassicaceae Arabidopsis thaliana.     

Putative candidate genes for blood pressure control in the SHR.BN-RNO8 congenic substrains

The SHR-Lx congenic strain carrying a differential segment of chromosome 8 of BN and PD origin was recently shown to exhibit a significant decrease in blood pressure as compared to the SHR strain. There were two positional candidate genes for blood pressure control mapped to the differential segment: the rat kidney epithelial potassium channel gene (Kcnj1) and brain dopamine receptor 2 gene (Drd2). Bot these genes were separated into SHR.BN-RNO8 congenic substrains. In this communication, we are presenting the assignment of two further putative candidate genes, which might be involved in blood pressure control to the BN/PD differential segment of the SHR-Lx congenic strain. These are: the gene coding for smooth muscle cell specific protein 22 (Sm22) defined by the D8Mcw1 marker and neuronal nicotinic acetylcholine receptor gene cluster, defined by the D8Bord1 marker. Moreover, the glutamate receptor gene Grik4 which also maps to the differential segment of the SHR-Lx should be taken into account. The genetic separation of all these putative candidate genes of blood pressure control is being performed by recombinations and subsequent selection using (SHR×SHR-Lx) intercross population.     

Immuno-electronmicroscopical localization of a microvillus membrane disaccharidase in the human small-intestinal epithelium with monoclonal antibodies

The cellular localization of the human intestinal disaccharidase, sucrase-isomaltase, was visualized in ultrathin cryosections by the use of specific monoclonal antibodies [25] followed by protein A-gold. The principle site of immunoreaction concerned the microvillus membrane, which supports current concepts of the localization of these hydrolases. One antibody against sucrase-isomaltase also showed labeling of the Golgi apparatus, apical vesicles, and lysosomes, but not of the basolateral membrane. The labeling of the Golgi complex was uniform, suggesting the absence of accumulation of sucrase-isomaltase in cisternae during its passage through this organelle. Absence of labeling of the basolateral membrane appears to support the view that newly synthesized sucrase-isomaltase is transferred directly from the Golgi complex to the microvillus membrane, bypassing the basolateral membrane. However, the results do not exclude the possibility of a very rapid passage through the basolateral membrane. A substantial fraction of the sucrase-isomaltase occurred in lysosomes, which indicates that this organelle plays a major role in the catabolism of microvillar hydrolases. Transport of sucrase-isomaltase to lysosomes might occur by endocytosis or via the crinophagic pathway. The latter was previously postulated to reflect a regulatory mechanism at the post-Golgi level for the surface expression of microvillar membrane proteins.     

Use of cytomorphometry and cytology in the diagnosis of transitional-cell carcinoma of the upper urinary tract

Because of the rise in incidence of upper urinary tract tumors, there is a need for a simple and reliable method for diagnosing these tumors, especially in people in a "high-risk" group. This retrospective study showed the usefulness of cytology and cytomorphometry in making the diagnosis of transitional-cell carcinoma of the upper urinary tract. The study also emphasized that the methods of collection and processing are of the utmost importance: the cytologic evaluation of ureteral catheterized urine specimens gave 100% accuracy as compared with a 40% false-negative rate in the cytologic diagnosis of voided urine specimens. A higher accuracy of urinary cytology for the diagnosis of upper urinary tract lesions clearly requires selective catheterization of the ureter. Objective cytomorphologic grading of the urinary cytology specimens was shown to compare favorably with histologic grading. Cytomorphologic grading not only can offer important information in determining the prognosis and in planning treatment but can also assist in quality control of other diagnostic methods and can help to resolve apparent diagnostic discrepancies.     

Photosynthesis by developing embryos of oilseed rape (Brassica napus L.)

The aim of this study was to assess the photosynthetic potentialof developing seeds of oilseed rape (Brassica napus L.) andto compare photosynthetic properties of embryo plastids withthose of leaf chloroplasts from the same species. Measurementsof CO₂-dependent O₂ evolution show that developing seeds ofB. napus are photosynthetically active in vitro. Essentially,all of the photosynthetic activity of the developing seed isaccounted for by the embryo. The rate of photosynthesis by developingembryos increased until the onset of desiccation, after whichit declined, so that by maturity embryos were no longer photosyntheticallyactive. Photosynthetic activity was positively correlated withchlorophyll content throughout development. Comparison of thephotosynthetic characteristics of leaf and embryo chloroplastsrevealed that rates of uncoupled electron transport were 2.5-foldgreater in those from the embryo. Light-saturated rates of CO₂-dependentO₂ evolution, per unit chlorophyll, and CO₂ saturation pointswere similar for chloroplasts from both tissues. However, light-saturationpoints and chlorophyll a/b ratios were lower for embryo thanfor leaf choroplasts. Embryos and embryo chloroplasts also containedconsiderably less ribulose 1,5-bisphosphate carboxylase/oxygenaseprotein per unit total protein, than leaves. Although excisedembryos were capable of high rates of CO₂-dependent O₂ evolution(90–100 mol mg^–1 chlorophyll h^–1) under asaturating photosynthetic photon flux density (PPFD), low transmittanceof light through the silique wall (30%), together with the highPPFD required to achieve light compensation points in developingseeds (500 mol m^–2 s^–1), suggests that photosynthesisin vivo is unlikely to make a net contribution to carbon economyunder normal environmental conditions. Key words: Embryo, development, photosynthesis, chloroplast, Brassica napus L.     

Large old trees increase growth under shifting climatic constraints: Aligning tree longevity and individual growth dynamics in primary mountain spruce forests

In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree-level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~5000 Norway spruce (Picea abies [L.] H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed-linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e., competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modeled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (>400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks.     

Trade-offs and synergies between ecosystem productivity and stability in temperate grasslands

Aim

It is crucial to monitor how the productivity of grasslands varies with its temporal stability for management of these ecosystems. However, identifying the direction of the productivity–stability relationship remains challenging because ecological stability has multiple components that can display neutral, positive or negative covariations. Furthermore, evidence suggests that the direction of the productivity–stability relationship depends on the biotic interactions and abiotic conditions that underlie ecosystem productivity and stability. We decipher the relationships between grassland productivity and two components of its stability in four habitat types with contrasting environments and flora.

Location

France.

Time period

2000–2020.

Major taxa

Grassland plant species.

Methods

We used c. 20,000 vegetation plots spread across French permanent grasslands and remotely sensed vegetation indices to quantify grassland productivity and temporal stability. We decomposed stability into constancy (i.e., temporal invariability) and resistance (i.e., maximum deviation from average) and deciphered the direct and indirect effects of abiotic (namely growing season length and nitrogen input) and biotic (namely plant taxonomic diversity, trait diversity and community-weighted mean traits) factors on productivity–stability relationships using structural equation models.

Results

We found a positive relationship between productivity and constancy and a negative relationship between productivity and resistance in all habitats. Abiotic factors had stronger effects on productivity and stability compared with biotic factors. A longer growing season enhanced grassland productivity and constancy. Nitrogen input had positive and negative effects on grassland productivity and resistance, respectively. Trait values affected the constancy and resistance of grassland more than taxonomic and trait diversity, with effects varying from one habitat to another. Productivity was not related to any biotic factor.

Main conclusions

Our findings reveal how vital it is to consider both the multiple components of stability and the interaction between environment and biodiversity to gain an understanding of the relationships between productivity and stability in real-world ecosystems, which is a crucial step for sustainable grassland management.