Fruit fly behavior in response to chemosensory signals

An important question in contemporary sensory neuroscience is how animals perceive their environment and make appropriate behavioral choices based on chemical perceptions. The fruit fly Drosophila melanogaster exhibits robust tastant and odor-evoked behaviors. Understanding how the gustatory and olfactory systems support the perception of these contact and volatile chemicals and translate them into appropriate attraction or avoidance behaviors has made an unprecedented contribution to our knowledge of the organization of chemosensory systems. In this review, I begin by describing the receptors and signaling mechanisms of the Drosophila gustatory and olfactory systems and then highlight their involvement in the control of simple and complex behaviors. The topics addressed include feeding behavior, learning and memory, navigation behavior, neuropeptide modulation of chemosensory behavior, and I conclude with a discussion of recent work that provides insight into pheromone signaling pathways.     

Summer water stress and shade alter bud size and budburst date in three mediterranean Quercus species

Current environmental conditions are known to affect plant growth, morphology, phenology, and therefore, plant performance. However, effects of the previous-year environmental conditions can also affect plant structure by altering bud growth, and proportion and date of budburst. Here, we analysed the effects of previous-year water stress and shade on bud size, percentage, and date of budburst in seedlings of three co-occurring Iberian Quercus species in two independent experiments. Responses of apical, lateral, and basal buds were checked during an annual cycle. In the first experiment, seedlings of two evergreens (Q. coccifera L., Q. ilex subsp. ballota (Desf.) Samp.) and a deciduous-marcescent tree (Q. faginea Lam.) were grown under two levels of summer watering. In the second experiment, seedlings were grown under three light intensities. Soluble sugars and starch in shoots and roots were measured before budburst. Summer drought increased bud size of all species and advanced budburst of Q. ilex and Q. coccifera. Moderate and/or intense shade tended to reduce bud size and delay budburst in all species. These responses seem related to changes in the date of bud formation rather than to the amount of carbon reserves, which were reduced both by drought and shade. Treatments affected percentage of budburst in lateral buds, which was reduced by shade and water stress, probably leading to narrower crowns. These results show that previous-year environmental conditions are relevant for plant phenology and structure. The different responses in budburst date between the deciduous and the evergreens might alter their competition relationships at seedling stage.     

Analysis of protein content in pollen loads produced in north-west Spain

An analysis was made of the protein content of pollen loads produced by the bees in a hive situated in Viana do Bolo (Ourense, north-west Spain), to establish whether or not the relative quantity of protein in the pollen of each plant species influences the preference made by the bee of the flowers that supply pollen to the hive. This analysis was performed on all types of pollen that formed more than 5% of the pollen spectrum. Pollen load samples were collected directly from the hive from March to September. Pollen loads were separated by colour, and their specific homogeneity was confirmed microscopically. The Bradford method has been used for protein extraction and spectrophotometry was used for the determination of protein content. The results show that the different pollen loads have high protein content. Pollen of the plant species that reached relatively higher percentages in the pollen spectrum are also those that have the highest protein content. These were Cytisus scoparius type, uncultivated Poaceae, Quercus robur type, Sanguisorba minor, Salix fragilis and Spergularia rubra type. The pollen of the systematic units, which had pollen loads that could be identified at the level of species, maintained a constant value of protein content independently of the date the samples were obtained. The pollen of the systematic units, which had pollen loads that could be identified at the level of pollen type, has varied in protein content in the analyses performed on samples obtained on different dates. This result is due to the fact that the different species that integrate the pollen type flower on different dates, and thus have a pollenkitt with different characteristics.     

Effect of elevated CO2, temperature and drought on photosynthesis of nodulated alfalfa during a cutting regrowth cycle

Rising atmospheric CO₂ may increase potential net leaf photosynthesis under short-term exposure, but this response decreases under long-term exposure because plants acclimate to elevated CO₂ concentrations through a process known as downregulation. One of the main factors that may influence this phenomenon is the balance between sources and sinks in the plant. The usual method of managing a forage legume like alfalfa requires the cutting of shoots and subsequent regrowth, which alters the source/sink ratio and thus photosynthetic behaviour. The aim of this study was to determine the effect of CO₂ (ambient, around 350 vs. 700 µmol mol⁻¹), temperature (ambient vs. ambient + 4° C) and water availability (well-irrigated vs. partially irrigated) on photosynthetic behaviour in nodulated alfalfa before defoliation and after 1 month of regrowth. At the end of vegetative normal growth, plants grown under conditions of elevated CO₂ showed photosynthetic acclimation with lower photosynthetic rates, V_cmax and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) activity. This decay was probably a consequence of a specific rubisco protein reduction and/or inactivation. In contrast, high CO₂ during regrowth did not change net photosynthetic rates or yield differences in V_cmax or rubisco total activity. This absence of photosynthetic acclimation was directly associated with the new source-sink status of the plants during regrowth. After cutting, the higher root/shoot ratio in plants and remaining respiration can function as a strong sink for photosynthates, avoiding leaf sugar accumulation, the negative feed-back control of photosynthesis, and as a consequence, photosynthetic downregulation.     

The effect of sample size and species characteristics on performance of different species distribution modeling methods

Species distribution models should provide conservation practioners with estimates of the spatial distributions of species requiring attention. These species are often rare and have limited known occurrences, posing challenges for creating accurate species distribution models. We tested four modeling methods (Bioclim, Domain, GARP, and Maxent) across 18 species with different levels of ecological specialization using six different sample size treatments and three different evaluation measures. Our assessment revealed that Maxent was the most capable of the four modeling methods in producing useful results with sample sizes as small as 5, 10 and 25 occurrences. The other methods compensated reasonably well (Domain and GARP) to poorly (Bioclim) when presented with datasets of small sample sizes. We show that multiple evaluation measures are necessary to determine accuracy of models produced with presence-only data. Further, we found that accuracy of models is greater for species with small geographic ranges and limited environmental tolerance, ecological characteristics of many rare species. Our results indicate that reasonable models can be made for some rare species, a result that should encourage conservationists to add distribution modeling to their toolbox.     

The Balearic Islands: a reservoir of cpDNA genetic variation for evergreen oaks

Aim To analyse the role of the Balearic Islands as a refuge area for evergreen Quercus (cork oak: Quercus suber L., holm oak: Q. ilex L., kermes oak: Q. coccifera L.), by using molecular, historical and palaeobotanical data. Location The Western Mediterranean Basin (Balearic Islands, eastern Iberia, Provence, Sardinia, Corsica, Sicily, Malta, Italy, Northern Africa). Methods We sampled 108 populations and used the PCR‐RFLP technique with five universal cpDNA primers to define haplotypes in the sampled populations. Diversity, differentiation parameters and spatial analysis of the populations, using a spatial version of amova , were linked to the geological history of the Western Mediterranean Basin in order to explain the present spatial pattern of the evergreen Quercus populations in the Balearics. Results Evergreen Quercus cpDNA shows a complex structure, with remnants of ancient diversity in the Balearics. Balearic populations of holm oak are related to Iberian populations, while for cork and kermes oaks, we found both Tyrrhenian and Iberian haplotypes. Main conclusions The complex spatial patterns of cpDNA in Balearic evergreen Quercus appears explicable in terms of a combination of physical (vicariance and long distance dispersal) and biological (introgressive hybridization) factors. The Balearics constitute a glacial refuge area and a reservoir of genetic variation with traces of ancient diversity from Messinian–Pliocene stages.     

Exploring the protein–protein interaction landscape in plants

Protein–protein interactions (PPIs) represent an essential aspect of plant systems biology. Identification of key protein players and their interaction networks provide crucial insights into the regulation of plant developmental processes and into interactions of plants with their environment. Despite the great advance in the methods for the discovery and validation of PPIs, still several challenges remain. First, the PPI networks are usually highly dynamic, and the in vivo interactions are often transient and difficult to detect. Therefore, the properties of the PPIs under study need to be considered to select the most suitable technique, because each has its own advantages and limitations. Second, besides knowledge on the interacting partners of a protein of interest, characteristics of the interaction, such as the spatial or temporal dynamics, are highly important. Hence, multiple approaches have to be combined to obtain a comprehensive view on the PPI network present in a cell. Here, we present the progress in commonly used methods to detect and validate PPIs in plants with a special emphasis on the PPI features assessed in each approach and how they were or can be used for the study of plant interactions with their environment.     

Acidithiobacillus thiooxidans secretome containing a newly described lipoprotein Licanantase enhances chalcopyrite bioleaching rate

The nature of the mineral–bacteria interphase where electron and mass transfer processes occur is a key element of the bioleaching processes of sulfide minerals. This interphase is composed of proteins, metabolites, and other compounds embedded in extracellular polymeric substances mainly consisting of sugars and lipids (Gehrke et al., Appl Environ Microbiol 64(7):2743–2747, 1998). On this respect, despite Acidithiobacilli—a ubiquitous bacterial genera in bioleaching processes (Rawlings, Microb Cell Fact 4(1):13, 2005)—has long been recognized as secreting bacteria (Jones and Starkey, J Bacteriol 82:788–789, 1961; Schaeffer and Umbreit, J Bacteriol 85:492–493, 1963), few studies have been carried out in order to clarify the nature and the role of the secreted protein component: the secretome. This work characterizes for the first time the sulfur (meta)secretome of Acidithiobacillus thiooxidans strain DSM 17318 in pure and mixed cultures with Acidithiobacillus ferrooxidans DSM 16786, identifying the major component of these secreted fractions as a single lipoprotein named here as Licanantase. Bioleaching assays with the addition of Licanantase-enriched concentrated secretome fractions show that this newly found lipoprotein as an active protein additive exerts an increasing effect on chalcopyrite bioleaching rate.