Winter feeding influences the cost of living in boreal passerines

The plastic regulation of internal energy reserves is acknowledged as the main adaptive response to winter conditions of resident small birds in northern latitudes, a strategy that may be altered whenever human‐supplemented food is available. We investigated the effects of supplementary feeding on the energy management strategy of two wild passerine species, the Willow Tit Poecile montanus and Blue Tit Cyanistes caeruleus, wintering in boreal conditions by measuring body mass and the energy cost of living, i.e. basal metabolic rate. Individuals of both species were heavier, larger and exhibited a higher energy cost of living when captured at the feeders than were individuals captured away from feeders. Fed Willow Tits expended more energy in maintenance, although this difference disappeared once mass was accounted for. Conversely, Blue Tits at feeders had higher mass‐adjusted energy cost of living, but only at low ambient temperatures. The results indicate that winter feeding has species‐specific effects on overall energy management strategy and modifies the response to environmental conditions of wintering passerines.     

Methodology to Improve the Efficiency of Evaluation of the Severity of Angular Leaf Spot in Common Bean

Disease severity assessment by means of a scoring scale, especially for angular leaf spot (Pseudocercospora griseola) in common bean, is hindered in experiments for assessment of progenies and/or breeding lines due to lack of uniformity of occurrence of the pathogens and segregation within progenies. The purpose of this study was to estimate the efficiency of the use of one plant per plot in assessing the severity of angular leaf spot in experiments for assessment of progenies and/or breeding lines in the common bean crop. To that end, two experimental strategies were used – one of them using one plant per plot and another using a standard size plot (SPP) (2–4‐m length rows). The experiments were conducted in the period from November 2011 to May 2012 in the municipalities of Lavras and Lambari, state of Minas Gerais, Brazil. Forty‐one lines from the breeding programme of the Universidade Federal de Lavras (UFLA) and from other research institutions were assessed, which differed in regard to their degree of susceptibility to P. griseola. The lines were assessed in regard to the severity of said disease using a five‐degree diagrammatic scale. In all the one plant per plot experiments, severity scores of angular leaf spot from the beginning of its occurrence, and later in intervals ranging from 7 to 12 days, were obtained. In the experiment with the SPP, assessment was made a few days prior to grain harvest. Estimates of the correlations between severity scores and grain yield (GY) were mostly of small magnitude. There was good coincidence between the lines classified as more resistant or more susceptible to the pathogen under the two conditions.     

An ecological cost associated with protective symbionts of aphids

Beneficial symbioses are widespread and diverse in the functions they provide to the host ranging from nutrition to protection. However, these partnerships with symbionts can be costly for the host. Such costs, so called “direct costs”, arise from a trade‐off between allocating resources to symbiosis and other functions such as reproduction or growth. Ecological costs may also exist when symbiosis negatively affects the interactions between the host and other organisms in the environment. Although ecological costs can deeply impact the evolution of symbiosis, they have received little attention. The pea aphid Acyrthosiphon pisum benefits a strong protection against its main parasitoids from protective bacterial symbionts. The ecological cost of symbiont‐mediated resistance to parasitism in aphids was here investigated by analyzing aphid behavior in the presence of predatory ladybirds. We showed that aphids harboring protective symbionts expressed less defensive behaviors, thus suffering a higher predation than symbiont‐free aphids. Consequently, our study indicates that this underlined ecological cost may affect both the coevolutionary processes between symbiotic partners and the prevalence of such beneficial bacterial symbionts in host natural populations.     

Carbon cost of plant nitrogen acquisition: global carbon cycle impact from an improved plant nitrogen cycle in the Community Land Model

Plants typically expend a significant portion of their available carbon (C) on nutrient acquisition – C that could otherwise support growth. However, given that most global terrestrial biosphere models (TBMs) do not include the C cost of nutrient acquisition, these models fail to represent current and future constraints to the land C sink. Here, we integrated a plant productivity‐optimized nutrient acquisition model – the Fixation and Uptake of Nitrogen Model – into one of the most widely used TBMs, the Community Land Model. Global plant nitrogen (N) uptake is dynamically simulated in the coupled model based on the C costs of N acquisition from mycorrhizal roots, nonmycorrhizal roots, N‐fixing microbes, and retranslocation (from senescing leaves). We find that at the global scale, plants spend 2.4 Pg C yr^?1 to acquire 1.0 Pg N yr^?1, and that the C cost of N acquisition leads to a downregulation of global net primary production (NPP) by 13%. Mycorrhizal uptake represented the dominant pathway by which N is acquired, accounting for ~66% of the N uptake by plants. Notably, roots associating with arbuscular mycorrhizal (AM) fungi – generally considered for their role in phosphorus (P) acquisition – are estimated to be the primary source of global plant N uptake owing to the dominance of AM‐associated plants in mid‐ and low‐latitude biomes. Overall, our coupled model improves the representations of NPP downregulation globally and generates spatially explicit patterns of belowground C allocation, soil N uptake, and N retranslocation at the global scale. Such model improvements are critical for predicting how plant responses to altered N availability (owing to N deposition, rising atmospheric CO₂, and warming temperatures) may impact the land C sink.     

BSKs are partially redundant positive regulators of brassinosteroid signaling in Arabidopsis

Arabidopsis thaliana brassinosteroid signaling kinases (BSKs) constitute a receptor‐like cytoplasmic kinase sub‐family (RLCK‐XII) with 12 members. Previous analysis demonstrated a positive role for BSK1 and BSK3 in the initial steps of brassinosteroid (BR) signal transduction. To investigate the function of BSKs in plant growth and BR signaling, we characterized T‐DNA insertion lines for eight BSK genes (BSK1–BSK8) and multiple mutant combinations. Simultaneous elimination of three BSK genes caused alterations in growth and the BR response, and the most severe phenotypes were observed in the bsk3,4,7,8 quadruple and bsk3,4,6,7,8 pentuple mutants, which displayed reduced rosette size, leaf curling and enhanced leaf inclination. In addition, upon treatment with 24‐epibrassinolide, these mutants showed reduced hypocotyl elongation, enhanced root growth and alteration in the expression of BR‐responsive genes. Some mutant combinations also showed antagonistic interactions. In support of a redundant function in BR signaling, multiple BSKs interacted in vivo with the BR receptor BRI1, and served as its phosphorylation substrates in vitro. The BIN2 and BIL2 GSK3‐like kinases, which are negative regulators of BR signaling, interacted in vivo with BSKs and phosphorylated them in vitro, probably at different sites to BRI1. This study demonstrates redundant biological functions for BSKs, and suggests the existence of a regulatory link between BSKs and GSK3‐like kinases.     

The diversion of 2‐C‐methyl‐d‐erythritol‐2,4‐cyclodiphosphate from the 2‐C‐methyl‐d‐erythritol 4‐phosphate pathway to hemiterpene glycosides mediates stress responses in Arabidopsis thaliana

2‐C‐Methyl‐d ‐erythritol‐2,4‐cyclodiphosphate (MEcDP) is an intermediate of the plastid‐localized 2‐C‐methyl‐d ‐erythritol‐4‐phosphate (MEP) pathway which supplies isoprenoid precursors for photosynthetic pigments, redox co‐factor side chains, plant volatiles, and phytohormones. The Arabidopsis hds‐3 mutant, defective in the 1‐hydroxy‐2‐methyl‐2‐(E)‐butenyl‐4‐diphosphate synthase step of the MEP pathway, accumulates its substrate MEcDP as well as the free tetraol 2‐C‐methyl‐d ‐erythritol (ME) and glucosylated ME metabolites, a metabolic diversion also occurring in wild type plants. MEcDP dephosphorylation to the free tetraol precedes glucosylation, a process which likely takes place in the cytosol. Other MEP pathway intermediates were not affected in hds‐3. Isotopic labeling, dark treatment, and inhibitor studies indicate that a second pool of MEcDP metabolically isolated from the main pathway is the source of a signal which activates salicylic acid induced defense responses before its conversion to hemiterpene glycosides. The hds‐3 mutant also showed enhanced resistance to the phloem‐feeding aphid Brevicoryne brassicae due to its constitutively activated defense response. However, this MEcDP‐mediated defense response is developmentally dependent and is repressed in emerging seedlings. MEcDP and ME exogenously applied to adult leaves mimics many of the gene induction effects seen in the hds‐3 mutant. In conclusion, we have identified a metabolic shunt from the central MEP pathway that diverts MEcDP to hemiterpene glycosides via ME, a process linked to balancing plant responses to biotic stress.     

The nutritional landscape of host plants for a specialist insect herbivore

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Plant defence induced by PGPR against Spodoptera litura in tomato (Solanum lycopersicum L.)

• The research conducted including its rationale: Spodoptera litura is the major pest of tomato causing significant reduction in tomato yield. Application of Plant growth promoting rhizobacteria(PGPR) prevent use of chemical fertilizer and synthetic pesticides through enhancement of plant growth and yield and induction of systemic resistance. Present investigation is an attempt to evaluate the role of PGPR, Pseudomonas putida and Rothia sp. on the physiology and yield of tomato fruit infested with the S. litura.
• Central methods applied : The surface sterilized seeds of tomato were inoculated with 48 h culture of P. putida and Rothia sp. At 6–7 branching stage of the plant, the larvae of S. litura at 2nd in star was used to infect the tomato plant leaves.
• Key results: The S. litura infestation decreased dry weight of shoots and roots by 46% and 22%, and significant reduction was recorded in tomato fruit yield. The P. putida and Rothia sp. inoculations alleviated the adverse effects of insect infestation and resulted in 60% increase in plant biomass and 40% increase in yield over infested plants.
• Main conclusions including key points of discussion: PGPR: Defense appears to be mediated via increase in proline production, enhanced activities of antioxidant enzymes, stimulation in the activities of protease and polyphenol oxidases, increased contents of phenolics, protein and chlorophyll. The formulation of biopesticide involving PGPR comprise an environment friendly and sustainable approach to overcome insect infestation.

     

Survival strategy of the endangered tree Acer catalpifolium Rehd., based on 13C fractionation

We conducted a field investigation and evaluation of ¹³C natural abundance to determine the growth habit and propagation strategy of Acer catalpifolium Rehd., a tree species native to China that is highly endangered. The results showed that A. catalpifolium is a K‐selected strategist and pioneer species. Its narrow ecological range limits its geographical distribution, and poor fecundity limits its population size. The analysis of ¹³C natural abundance showed that A. catalpifolium does not use organic matter for reproduction when its stand volume is less than 1.08 × 10⁶ cm³ or it is less than 18.6 m tall, but it does use this strategy when it has a sufficient 1.08 × 10⁶ cm³ stand volume or more or is taller than 18.6 m. If environmental conditions are not conducive (e.g., severe human disturbance, cliff edges, or fierce interspecific competition) to the continued growth of the tree, A. catalpifolium may allocate organic matter for reproduction. Human disturbance seems to promote the population expansion of A. catalpifolium. We provide our suggestions for the promotion and protection of A. catalpifolium as a species.     

Using GPS telemetry to validate least‐cost modeling of gray squirrel (Sciurus carolinensis) movement within a fragmented landscape

In Britain, the population of native red squirrels Sciurus vulgaris has suffered population declines and local extinctions. Interspecific resource competition and disease spread by the invasive gray squirrel Sciurus carolinensis are the main factors behind the decline. Gray squirrels have adapted to the British landscape so efficiently that they are widely distributed. Knowledge on how gray squirrels are using the landscape matrix and being able to predict their movements will aid management. This study is the first to use global positioning system (GPS) collars on wild gray squirrels to accurately record movements and land cover use within the landscape matrix. This data were used to validate Geographical Information System (GIS) least‐cost model predictions of movements and provided much needed information on gray squirrel movement pathways and network use. Buffered least‐cost paths and least‐cost corridors provide predictions of the most probable movements through the landscape and are seen to perform better than the more expansive least‐cost networks which include all possible movements. Applying the knowledge and methodologies gained to current gray squirrel expansion areas, such as Scotland and in Italy, will aid in the prediction of potential movement areas and therefore management of the invasive gray squirrel. The methodologies presented in this study could potentially be used in any landscape and on numerous species.     

Influence of oxidative homeostasis on bacterial density and cost of infection in Drosophila–Wolbachia symbioses

The evolution of symbioses along the continuum between parasitism and mutualism can be influenced by the oxidative homeostasis, that is the balance between reactive oxygen species (ROS) and antioxidant molecules. Indeed, ROS can contribute to the host immune defence to regulate symbiont populations, but are also toxic. This interplay between ROS and symbiosis is notably exemplified by recent results in arthropod–Wolbachia interactions. Wolbachia are symbiotic bacteria involved in a wide range of interactions with their arthropods hosts, from facultative, parasitic associations to obligatory, mutualistic ones. In this study, we used Drosophila–Wolbachia associations to determine whether the oxidative homeostasis plays a role in explaining the differences between phenotypically distinct arthropod–Wolbachia symbioses. We used Drosophila lines with different Wolbachia infections and measured the effects of pro‐oxidant (paraquat) and antioxidant (glutathione) treatments on the Wolbachia density and the host survival. We show that experimental manipulations of the oxidative homeostasis can reduce the cost of the infection through its effect on Wolbachia density. We discuss the implication of this result from an evolutionary perspective and argue that the oxidative homeostasis could underlie the evolution of tolerance and dependence on Wolbachia.     

Asynchronous hatching provides females with a means for increasing male care but incurs a cost by reducing offspring fitness

In species with biparental care, sexual conflict occurs because the benefit of care depends on the total amount of care provided by the two parents while the cost of care depends on each parent's own contribution. Asynchronous hatching may play a role in mediating the resolution of this conflict over parental care. The sexual conflict hypothesis for the evolution of asynchronous hatching suggests that females adjust hatching patterns in order to increase male parental effort relative to female effort. We tested this hypothesis in the burying beetle Nicrophorus vespilloides by setting up experimental broods with three different hatching patterns: synchronous, asynchronous and highly asynchronous broods. As predicted, we found that males provided care for longer in asynchronous broods whereas the opposite was true of females. However, we did not find any benefit to females of reducing their duration of care in terms of increased lifespan or reduced mass loss during breeding. We found substantial negative effects of hatching asynchrony on offspring fitness as larval mass was lower and fewer larvae survived to dispersal in highly asynchronous broods compared to synchronous or asynchronous broods. Our results suggest that, even though females can increase male parental effort by hatching their broods more asynchronously, females pay a substantial cost from doing so in terms of reducing offspring growth and survival. Thus, females should be under selection to produce a hatching pattern that provides the best possible trade‐off between the benefits of increased male parental effort and the costs due to reduced offspring fitness.     

Roq1 mediates recognition of the Xanthomonas and Pseudomonas effector proteins XopQ and HopQ1

Xanthomonas spp. are phytopathogenic bacteria that can cause disease on a wide variety of plant species resulting in significant impacts on crop yields. Limited genetic resistance is available in most crop species and current control methods are often inadequate, particularly when environmental conditions favor disease. The plant Nicotiana benthamiana has been shown to be resistant to Xanthomonas and Pseudomonas due to an immune response triggered by the bacterial effector proteins XopQ and HopQ1, respectively. We used a reverse genetic screen to identify Recognition of XopQ 1 (Roq1), a nucleotide‐binding leucine‐rich repeat (NLR) protein with a Toll‐like interleukin‐1 receptor (TIR) domain, which mediates XopQ recognition in N. benthamiana. Roq1 orthologs appear to be present only in the Nicotiana genus. Expression of Roq1 was found to be sufficient for XopQ recognition in both the closely‐related Nicotiana sylvestris and the distantly‐related beet plant (Beta vulgaris). Roq1 was found to co‐immunoprecipitate with XopQ, suggesting a physical association between the two proteins. Roq1 is able to recognize XopQ alleles from various Xanthomonas species, as well as HopQ1 from Pseudomonas, demonstrating widespread potential application in protecting crop plants from these pathogens.     

Resistance evaluation of wheat germplasm containing Dn4 or Dny against Russian wheat aphid biotype RWASA3

Host plant resistance can effectively manage Russian wheat aphid (Diuraphis noxia) Kurdjumov (Homoptera: Aphididae) in areas where it is an economically important pest of wheat. However, biotypes of D. noxia virulent on wheat containing resistance gene Dn4 have been reported in both the United States and South Africa. Thirty wheat genotypes, including susceptible Yuma, resistant CItr2401, as well as 25 genotypes containing Dn4 and three genotypes containing Dny were planted under greenhouse conditions in Bethlehem, South Africa, and screened with D. noxia biotype RWASA3. RWASA3 caused susceptible damage symptoms in MTRWA92‐145, Ankor, Halt, Bond CL, 18FAWWON‐SA 262, Prowers99, 18FAWWON‐SA 264, Hatcher, Yumar, Corwa and Thunder CL all reported to contain the Dn4 resistance gene. Genotypes PI586956, Stanton and 18FAWWON‐SA 257, containing the Dny‐resistance gene were susceptible to RWASA3. Similarly, coinciding development of virulence to resistance genes Dn4 and Dny was reported in the United States. However, in this study, 13 Dn4‐containing genotypes showed moderate resistance when screened with RWASA3 alluding to a more complex biotype‐gene‐interaction. These findings could indicate that Dn4 and Dny may be related and possibly share a similar or common resistance factor. Further studies will be aimed at explaining these results investigating the possibility of an allelic cluster or series for Dn4, possibly including Dny.     

Does acoustic priming ‘sweeten the pot’ of floral nectar?

A recent claim that evening primrose flowers adaptively secrete nectar in response to vibrations from hovering bees lacks supporting evidence. The authors fail to demonstrate that bees can access the concealed nectar and that their visits enhance plant fitness. Reanalysis of the authors’ data raises additional concerns about their conclusions.     

Salinity and crop yield

Thirty crop species provide 90% of our food, most of which display severe yield losses under moderate salinity. Securing and augmenting agricultural yield in times of global warming and population increase is urgent and should, aside from ameliorating saline soils, include attempts to increase crop plant salt tolerance. This short review provides an overview of the processes that limit growth and yield in saline conditions. Yield is reduced if soil salinity surpasses crop‐specific thresholds, with cotton, barley and sugar beet being highly tolerant, while sweet potato, wheat and maize display high sensitivity. Apart from Na⁺, also Cl^?, Mg²⁺, SO₄^2‐ or HCO₃^‐ contribute to salt toxicity. The inhibition of biochemical or physiological processes cause imbalance in metabolism and cell signalling and enhance the production of reactive oxygen species interfering with cell redox and energy state. Plant development and root patterning is disturbed, and this response depends on redox and reactive oxygen species signalling, calcium and plant hormones. The interlink of the physiological understanding of tolerance processes from molecular processes as well as the agronomical techniques for stabilizing growth and yield and their interlinks might help improving our crops for future demand and will provide improvement for cultivating crops in saline environment.     

The influence of rice plant age on susceptibility to the rice water weevil,Lissorhoptrus oryzophilus

Plant age‐ and plant stage‐related changes in the resistance of rice, Oryza sativa, to its most important insect pest in the US, the rice water weevil (Lissorhoptrus oryzophilus), were investigated in a series of field and greenhouse choice and no‐choice studies. Rice plants were susceptible to infestation by rice water weevils over a broad range of plant ontogenetic stages, from at least the early vegetative stage to well into the reproductive stage. There was, however, a clear preference expressed by rice water weevils in both choice and no‐choice experiments for plants in (or nearly in) the tillering stage of development, with pre‐tillering and reproductive stage plants less preferred. The relationship between rice plant age and susceptibility to weevils is thus nonlinear. This study constitutes one of the most thorough studies to date of the relationship in a grass species between plant age and susceptibility to herbivores. The results provide a biological explanation for observed patterns of weevil infestations and a rationale for the cultural practice of delayed flooding.     

Identification and Pathogenicity of Lasiodiplodia Species from Eucalyptus urophylla × grandis,Polyscias balfouriana and Bougainvillea spectabilis in Southern China

Species of Lasiodiplodia are important pathogens of a wide variety of plants covering a wide geographical distribution. These fungi can be associated with different symptoms such as stem cankers, shoot blights, fruit rots, dieback and gummosis. Diseases caused by Lasiodiplodia were surveyed on Eucalyptus urophylla × grandis, Polyscias balfouriana and Bougainvillea spectabilis in a nursery in southern China. Based on morphology characteristics and phylogenetic analyses of ITS rDNA sequences and translation elongation factor 1‐alpha (TEF‐1α) gene regions, four species of Lasiodiplodia were identified. Lasiodiplodia theobromae was identified from E. urophylla × grandis, P. balfouriana and B. spectabilis. L. hormozganensis, L. iraniensis and L. pseudotheobromae were identified from B. spectabilis. To our knowledge, with the exception of L. theobromae on E. urophylla × grandis, this study represents the first report of these fungi on the host plants. Pathogenicity tests showed that all Lasiodiplodia spp. obtained in this study are virulent to E. urophylla × grandis and B. spectabilis, and L. theobromae was virulent to P. balfouriana.     

Honey bee hygienic behaviour does not incur a cost via removal of healthy brood

In the honey bee, hygienic behaviour, the removal of dead or diseased brood from capped cells by workers, is a heritable trait that confers colony‐level resistance against brood diseases. This behaviour is quite rare. Only c. 10% of unselected colonies show high levels of hygiene. Previous studies suggested that hygiene might be rare because it also results in the removal of healthy brood, thereby imposing an ongoing cost even when brood diseases are absent. We tested this hypothesis by quantifying hygienic behaviour in 10 colonies using a standard technique, the freeze‐killed brood (FKB) bioassay. At the same time, we also quantified the removal of untreated brood. The study colonies showed a wide range in hygienic behaviour, removing 19.7–100% of the FKB. The removal of untreated brood ranged from 2% to 44.4%. However, there was no correlation between the two removal rates for any of the four age groups of untreated brood studied (eggs, young larvae, older larvae from uncapped cells and larvae/pupae from capped cells). These results do not support the cost‐to‐healthy‐brood hypothesis for the rarity of hygienic behaviour.     

The Antimicrobial Peptide Thanatin Reduces Fungal Infections in Arabidopsis

We explored the antifungal activity of thanatin, a 21 amino acid synthetic peptide from the hemipteran spined soldier bug Podisus maculiventris, against the mycotoxin‐producing plant pathogenic ascomycete Fusarium graminearum. In vitro germination assays showed complete inhibition of macroconidia germination and mycelia growth by >10 μm thanatin. Moreover, detached leaves of thanatin‐expressing Arabidopsis thaliana plants displayed enhanced resistance towards colonization with F. graminearum. Consistent with this, the plants showed also enhanced resistance of detached leaves to colonization with Botrytis cinerea. The results demonstrate a potential of thanatin for use in plant protection.