Pre-attachment Striga hermonthica resistance of New Rice for Africa (NERICA) cultivars based on low strigolactone production

Striga hermonthica (Striga) is an obligate hemiparasitic weed, causing severe yield losses in cereals, including rice, throughout sub-Saharan Africa. Striga germination depends on strigolactones (germination stimulants) exuded by the host roots. The interspecific New Rice for Africa (NERICA) cultivars offer a potentially interesting gene pool for a screen for low germination-inducing rice cultivars. Exudates were collected from all NERICA cultivars and their parents (Oryza sativa and Oryza glaberrima) for the analysis of strigolactones. In vitro and in situ Striga germination, attachment and emergence rates were recorded for each cultivar. NERICA 1 and CG14 produced significantly less strigolactones and showed less Striga infection than the other cultivars. NERICAs 7, 8, 11 and 14 produced the largest amounts of strigolactones and showed the most severe Striga infection. Across all the cultivars and parents, there was a positive relationship between the amount of strigolactones in the exudate and Striga germination, attachment and emergence rates. This study shows that there is genetic variation in Striga pre-attachment resistance in NERICA rice. Cultivars combining this pre-attachment resistance with post-attachment resistance (already identified) can provide a key component for durable integrated management of this noxious weed in cereal production systems in sub-Saharan Africa.     

Inter-annual variations in biomass of loose lying algae Furcellaria-Coccotylus community: The relative importance of local versus regional environmental factors in the West Estonian Archipelago

The effects of local nutrient loading, harvesting, regional temperature patterns and weather induced light conditions were assessed on the interannual dynamics of the commercially important loose-lying red algal community of Furcellaria lumbricalis and Coccotylus truncatus. Higher algal biomasses were due to higher temperatures and number of calm days (i.e. clear water phases) during the active growing season in spring and summer. In addition, higher biomasses were associated with a higher number of stormy days in November-February, which is linked to a reduced ice cover and longer growing season. Commercial harvesting and nutrient load did not appear to drive the interannual dynamics of these red algae. Thus, the dynamics of the loose-lying red algal community is constrained by regional rather than local environmental factors.     

Factors controlling long-term changes of the eutrophicated ecosystem of Pärnu Bay,Gulf of Riga

Phytoplankton, mesozooplankton, mysids and fish larvae were studied during 15–29 annual cycles measured weekly to monthly in Pärnu Bay, the Gulf of Riga. The monthly variability of the biological data was related to temperature, ice conditions, salinity, influx of nutrients, the North Atlantic Oscillation (NAO) index, cloudiness and solar activity. Phytoplankton development was mainly a function of the NAO index. For the whole study period the abundance of zooplankton increased with increasing water temperature and solar activity. Significant correlations between phytoplankton and zooplankton densities were found until 1990. After the invasion of the predatory cladoceran Cercopagis pengoi in 1991, the zooplankton community was likely to be regulated by the introduced species rather than phytoplankton dynamics. The increased abundances of rotifers and copepods triggered the increase in mysid densities. The development of herring larvae was positively affected by the high density of copepods and rotifers but also by increased eutrophication. Until 1990 there was no significant relationship between the density of zooplankton and herring larvae. A negative relationship between the density of zooplankton and herring larvae in the 1990s suggests that the major shift in zooplankton community resulted in food limitation for herring larvae. The results indicated that (1) atmospheric processes in the northern Atlantic explain a large part of the interannual variation of the local phytoplankton stock, (2) trophic interactions control the development of pelagic communities at higher trophic levels, and (3) the introduction of an effective intermediate predator has repercussions for the whole pelagic food web in Pärnu Bay.     

Predicting Species Cover of Marine Macrophyte and Invertebrate Species Combining Hyperspectral Remote Sensing,Machine Learning and Regression Techniques

In order to understand biotic patterns and their changes in nature there is an obvious need for high-quality seamless measurements of such patterns. If remote sensing methods have been applied with reasonable success in terrestrial environment, their use in aquatic ecosystems still remained challenging. In the present study we combined hyperspectral remote sensing and boosted regression tree modelling (BTR), an ensemble method for statistical techniques and machine learning, in order to test their applicability in predicting macrophyte and invertebrate species cover in the optically complex seawater of the Baltic Sea. The BRT technique combined with remote sensing and traditional spatial modelling succeeded in identifying, constructing and testing functionality of abiotic environmental predictors on the coverage of benthic macrophyte and invertebrate species. Our models easily predicted a large quantity of macrophyte and invertebrate species cover and recaptured multitude of interactions between environment and biota indicating a strong potential of the method in the modelling of aquatic species in the large variety of ecosystems.     

Unveiling commonalities in understudied habitats of boulder-reefs: life-history traits of the widespread invertebrate and algal inhabitants

Compared to stable reef habitats, dynamic boulder-reefs (commonly called boulder-fields when intertidal) host many habitat specialist species. Most occur underneath boulders where they are largely hidden from view; only limited research has assessed their life-histories despite their widespread importance for biological diversity. But some abundant under-boulder species likely structuring this system are habitat generalists widely researched elsewhere. Here we review this research, focusing on three widespread under-boulder sessile taxa: spirorbids, serpulids (tubeworms) and nongeniculate coralline algae, and three mobile taxa: sea urchins, chitons and crabs. Spirorbids have extensive reproductive/colonization capabilities but are readily out-competed. We thus characterize spirorbids as mostly early-successional, while serpulids often have greater competitiveness. Nongeniculate corallines occur underneath boulders where light reaches, although they can withstand low levels of that and most other resources. Such traits characterize nongeniculate corallines as late-successional. Thus, succession underneath boulders may shift deterministically from early tubeworms to late nongeniculate corallines. Habitat generalist sea urchin and chiton species often have strong inter-specific interactions in exposed habitats. Future experiments may find that under-boulder aggregations of these taxa, and also crabs, are impacting algal and invertebrate assemblages. These experiments will be required if dynamic boulder-reefs are to be as thoroughly understood as other benthic systems.     

How Much Overtesting Is Needed to Safely Exclude a Diagnosis? A Different Perspective on Triage Testing Using Bayes' Theorem

Ruling out disease often requires expensive or potentially harmful confirmation testing. For such testing, a less invasive triage test is often used. Intuitively, few negative confirmatory tests suggest success of this approach. However, if negative confirmation tests become too rare, too many disease cases could have been missed. It is therefore important to know how many negative tests are needed to safely exclude a diagnosis. We quantified this relationship using Bayes’ theorem, and applied this to the example of pulmonary embolism (PE), for which triage is done with a Clinical Decision Rule (CDR) and D-dimer testing, and CT-angiography (CTA) is the confirmation test. For a maximum proportion of missed PEs of 1% in triage-negative patients, we calculate a 67% ''mandatory minimum'' proportion of negative CTA scans. To achieve this, the proportion of patients with PE undergoing triage testing should be appropriately low, in this case no higher than 24%. Pre-test probability, triage test characteristics, the proportion of negative confirmation tests, and the number of missed diagnoses are mathematically entangled. The proportion of negative confirmation tests—not too high, but definitely not too low either—could be a quality benchmark for diagnostic processes.     

Distribution and population characteristics of the alien talitrid amphipod Orchestia cavimana in relation to environmental conditions in the Northeastern Baltic Sea

The talitrid amphipods were found for the first time in the Northeastern Baltic Sea in 1999. Orchestia cavimana inhabited damp wracks cast up on shore within a 200 m area of Saaremaa Island. In the following year, the species expanded its range to a few kilometres. In 2002, six additional locations of O. cavimana were found in Saaremaa Island and two locations in the Northwestern part of Estonia. Abundances and biomasses were highest in the first year of the invasion. In the following years, the values stabilized on remarkably lower levels. Population characteristics of the species varied significantly between locations. The average biomass and abundance were 9 g dw m⁻² and 1975 ind m⁻², respectively. Wrack biomass and interaction between wrack biomass and exposure were the best predictors of the abundances and biomasses of O. cavimana. Humidity explained additional variability in biomasses. The size structure of the population of O. cavimana was mostly related to humidity and wrack biomass. The Southern coast of the Baltic Sea may be regarded as the initial donor region for the Estonian populations of O. cavimana. The vector of this invasion is most likely related to the natural dispersal of the drifting algae but human activities as a transport vector can not be excluded. The incredible speed of the invasion of O. cavimana and its high biomasses indicate that the species will very likely extend its distribution along the coast of the Northeastern Baltic Sea in the following years.     

Five challenges to bringing single-molecule force spectroscopy into living cells

In recent years, single-molecule force spectroscopy techniques have been used to study how inter- and intramolecular interactions control the assembly and functional state of biomolecular machinery in vitro. Here we discuss the problems and challenges that need to be addressed to bring these technologies into living cells and to learn how cellular machinery is controlled in vivo.     

Stay Tuned: What Is Special About Not Shifting Attention?

Background

When studying attentional orienting processes, brain activity elicited by symbolic cue is usually compared to a neutral condition in which no information is provided about the upcoming target location. It is generally assumed that when a neutral cue is provided, participants do not shift their attention. The present study sought to validate this assumption. We further investigated whether anticipated task demands had an impact on brain activity related to processing symbolic cues.

Methodology/Principal Findings

Two experiments were conducted, during which event-related potentials were elicited by symbolic cues that instructed participants to shift their attention to a particular location on a computer screen. In Experiment 1, attention shift-inducing cues were compared to non-informative cues, while in both conditions participants were required to detect target stimuli that were subsequently presented at peripheral locations. In Experiment 2, a non-ambiguous “stay-central” cue that explicitly required participants not to shift their attention was used instead. In the latter case, target stimuli that followed a stay-central cue were also presented at a central location. Both experiments revealed enlarged early latency contralateral ERP components to shift-inducing cues compared to those elicited by either non-informative (exp. 1) or stay-central cues (exp. 2). In addition, cueing effects were modulated by the anticipated difficulty of the upcoming target, particularly so in Experiment 2. A positive difference, predominantly over the posterior contralateral scalp areas, could be observed for stay-central cues, especially for those predicting that the upcoming target would be easy. This effect was not present for non-informative cues.

Conclusions/Significance

We interpret our result in terms of a more rapid engagement of attention occurring in the presence of a more predictive instruction (i.e. stay-central easy target). Our results indicate that the human brain is capable of very rapidly identifying the difference between different types of instructions.