The cuticle on the gametophyte calyptra matures before the sporophyte cuticle in the moss Funaria hygrometrica (Funariaceae)

? Premise of the study: In vascular plants, leaf primordia prevent desiccation of the shoot apical meristem. Lacking leaves, the undifferentiated moss sporophyte apex is covered by the calyptra, a cap of maternal gametophyte tissue that is hypothesized to function in desiccation protection. Herein, we compare cuticle development on the calyptra and sporophyte to assess the calyptra's potential to protect the sporophyte from desiccation. As the first comprehensive study of moss sporophyte cuticle development, this research broadens our perspectives on cuticle development and evolution across embryophytes. ? Methods: Calyptrae and sporophytes at nine developmental stages were collected from a laboratory-grown population of the moss Funaria hygrometrica. Tissues were embedded, sectioned, then examined using transmission electron microscopy. Epidermal cells were measured for thickness of the cuticle layers, cell wall thickness, and lumen size. ? Key results: The calyptra cuticle develops precociously and reaches maturity before the sporophyte cuticle. Calyptrae are covered by a four-layered cuticle at all stages, whereas sporophyte cuticle maturation is delayed until sporangium formation. The development and thickening of the sporophyte cuticle occurs in an acropetal wave. ? Conclusions: A multilayered calyptra cuticle at the earliest developmental stages is consistent with its ability to protect the immature sporophyte from desiccation. Young sporophytes lack a complex cuticle and thus may require protection, whereas in older sporophytes a mature cuticle develops. The moss calyptra is not a vestigial structure, but rather the calyptra's role in preventing desiccation offers a functional explanation for calyptra retention during the 450 Myr of moss evolution.     

The Global Trade in Fresh Produce and the Vagility of Plant Viruses: A Case Study in Garlic

As cuisine becomes globalized, large volumes of fresh produce are traded internationally. The potential exists for pathogens infecting fresh produce to hitchhike to new locations and perhaps to establish there. It is difficult to identify them using traditional methods if pathogens are novel, scarce, and/or unexpected. In an attempt to overcome this limitation, we used high-throughput sequencing technology as a means of detecting all RNA viruses infecting garlic (Allium sativum L.) bulbs imported into Australia from China, the USA, Mexico, Argentina and Spain, and those growing in Australia. Bulbs tested were grown over multiple vegetative generations and all were stably infected with one or more viruses, including two species not previously recorded in Australia. Present in various combinations from 10 garlic bulbs were 41 virus isolates representing potyviruses (Onion yellow dwarf virus, Leek yellow stripe virus), carlaviruses (Shallot latent virus, Garlic common latent virus) and allexiviruses (Garlic virus A, B, C, D, and X), for which 19 complete and 22 partial genome sequences were obtained, including the first complete genome sequences of two isolates of GarVD. The most genetically distinct isolates of GarVA and GarVX described so far were identified from Mexico and Argentina, and possible scenarios explaining this are presented. The complete genome sequence of an isolate of the potexvirus Asparagus virus 3 (AV3) was obtained in Australia from wild garlic (A. vineale L.), a naturalized weed. This is first time AV3 has been identified from wild garlic and the first time it has been identified beyond China and Japan. The need for routine generic diagnosis and appropriate legislation to address the risks to primary production and wild plant communities from pathogens spread through the international trade in fresh produce is discussed.     

Endoplasmic reticulum-quality control chaperones facilitate the biogenesis of Cf receptor-like proteins involved in pathogen resistance of tomato

Cf proteins are receptor-like proteins (RLPs) that mediate resistance of tomato (Solanum lycopersicum) to the foliar pathogen Cladosporium fulvum. These transmembrane immune receptors, which carry extracellular leucine-rich repeats that are subjected to posttranslational glycosylation, perceive effectors of the pathogen and trigger a defense response that results in plant resistance. To identify proteins required for the functionality of these RLPs, we performed immunopurification of a functional Cf-4-enhanced green fluorescent protein fusion protein transiently expressed in Nicotiana benthamiana, followed by mass spectrometry. The endoplasmic reticulum (ER) heat shock protein70 binding proteins (BiPs) and lectin-type calreticulins (CRTs), which are chaperones involved in ER-quality control, were copurifying with Cf-4-enhanced green fluorescent protein. The tomato and N. benthamiana genomes encode four BiP homologs and silencing experiments revealed that these BiPs are important for overall plant viability. For the three tomato CRTs, virus-induced gene silencing targeting the plant-specific CRT3a gene resulted in a significantly compromised Cf-4-mediated defense response and loss of full resistance to C. fulvum. We show that upon knockdown of CRT3a the Cf-4 protein accumulated, but the pool of Cf-4 protein carrying complex-type N-linked glycans was largely reduced. Together, our study on proteins required for Cf function reveals an important role for the CRT ER chaperone CRT3a in the biogenesis and functionality of this type of RLP involved in plant defense.     

Local signaling within stem cell niches: insights from Drosophila

Tissue stem cells are found in specialized microenvironments (niches) where they are exposed to diverse systemic and local signals that are integrated with cell intrinsic factors to regulate stem cell behavior. In general, systemic signals are utilized to coordinate the response of tissues to acute or long-term changes that affect the whole organism, such as variations in nutrient availability or aging. In contrast, local signaling regulates tissue maintenance by balancing stem cell self-renewal with differentiation under homeostatic conditions and in response to local damage. In this review, we highlight the role of the JAK-STAT pathway in two Drosophila stem cell systems, the testis and intestine, and compare and contrast how activation of this pathway leads to tissue maintenance under both homeostatic conditions and in response to stress or injury.     

A high-throughput chemically induced inflammation assay in zebrafish

Background  

Studies on innate immunity have benefited from the introduction of zebrafish as a model system. Transgenic fish expressing fluorescent proteins in leukocyte populations allow direct, quantitative visualization of an inflammatory response in vivo. It has been proposed that this animal model can be used for high-throughput screens aimed at the identification of novel immunomodulatory lead compounds. However, current assays require invasive manipulation of fish individually, thus preventing high-content screening.     

Behavioural thermoregulation and climatic range restriction in the globally threatened Ethiopian Bush‐crow Zavattariornis stresemanni

Climate may influence the distribution and abundance of a species through a number of demographic and ecological processes, but the proximate drivers of such responses are only recently being identified. The Ethiopian Bush‐crow Zavattariornis stresemanni is a starling‐like corvid that is restricted to a small region of southern Ethiopia. It is classified as Endangered in the IUCN Red List of globally threatened species. Previous work suggested that this range restriction is almost perfectly defined by a climate envelope that is cooler than surrounding areas, but the proximate mechanism remains unexplained. The heavily altered habitats which the species inhabits are widespread across Africa, and recent work has shown that the Bush‐crow is behaviourally adaptable and has a catholic diet. We assess whether its enigmatic distribution can be explained by behavioural responses to the higher temperatures that surround its current range. Using environmental niche models and field observations of thermally mediated behaviour, we compare the range restriction and behavioural thermoregulation of the Ethiopian Bush‐crow with those of two sympatric control species that are similar in size and ecology, but have much larger ranges that include hotter environments. White‐crowned Starling Lamprotornis albicapillus and Superb Starling L. superbus occupy similar habitats to the Ethiopian Bush‐crow and all three frequently forage together. We found that the Bush‐crow's range is limited primarily by temperature, with a secondary effect of dry season rainfall, whereas the ranges of the two starling species are better predicted by wet season rainfall alone. Bush‐crows exhibited panting behaviour and moved into the shade of trees at significantly lower ambient temperatures than did the starlings, and their food intake declined more steeply with increasing temperature. These results indicate that the limited geographical range of the Bush‐crow reflects an inability to cope with higher temperatures. This suggests that a species' response to climate change might not be easily predicted by its ecological generalism, and may represent an inherited debt from its evolutionary history.     

Seed size,number and strategies in annual plants: a comparative functional analysis and synthesis

Background and AimsPlants depend fundamentally on establishment from seed. However, protocols in trait-based ecology currently estimate seed size but not seed number. This can be rectified. For annuals, seed number should simply be a positive function of vegetative biomass and a negative function of seed size.MethodsUsing published values of comparative seed number as the ‘gold standard’ and a large functional database, comparative seed yield and number per plant and per m² were predicted by multiple regression. Subsequently, ecological variation in each was explored for English and Spanish habitats, newly calculated C-S-R strategies and changed abundance in the British flora.Key ResultsAs predicted, comparative seed mass yield per plant was consistently a positive function of plant size and competitive ability, and largely independent of seed size. Regressions estimating comparative seed number included, additionally, seed size as a negative function. Relationships differed numerically between regions, habitats and C-S-R strategies. Moreover, some species differed in life history over their geographical range. Comparative seed yield per m² was positively correlated with FAO crop yield, and increasing British annuals produced numerous seeds. Nevertheless, predicted values must be viewed as comparative rather than absolute: they varied according to the ‘gold standard’ predictor used. Moreover, regressions estimating comparative seed yield per m² achieved low precision.ConclusionsFor the first time, estimates of comparative seed yield and number for >800 annuals and their predictor equations have been produced and the ecological importance of these regenerative traits has been illustrated. ‘Regenerative trait-based ecology’ remains in its infancy, with work needed on determinate vs. indeterminate flowering (‘bet-hedging’), C-S-R methodologies, phylogeny, comparative seed yield per m² and changing life history. Nevertheless, this has been a positive start and readers are invited to use estimates for >800 annuals, in the Supplementary data, to help advance ‘regenerative trait-based ecology’ to the next level.     

Comparison of transcript profiles in different life stages of the nematode Globodera pallida under different host potato genotypes

The potato cyst nematodes (PCNs) Globodera pallida and Globodera rostochiensis are important parasites of potato. PCNs undergo complex biotrophic interactions with their hosts that involve gene expression changes in both the nematode and the host plant. The aim of this study was to determine key genes that are differentially expressed in Globodera pallida life cycle stages and during the initiation of the feeding site in susceptible and partially resistant potato genotypes. For this purpose, two microarray experiments were designed: (i) a comparison of eggs, infective second‐stage juveniles (J2s) and sedentary parasitic‐stage J2s (SJ2); (ii) a comparison of SJ2s at 8 days after inoculation (DAI) in the susceptible cultivar (Desirée) and two partially resistant lines. The results showed differential expression of G. pallida genes during the stages studied, including previously characterized effectors. In addition, a large number of genes changed their expression between SJ2s in the susceptible cultivar and those infecting partially resistant lines; the number of genes with modified expression was lower when the two partially resistant lines were compared. Moreover, a histopathological study was performed at several time points (7, 14 and 30 DAI) and showed the similarities between both partially resistant lines with a delay and degeneration in the formation of the syncytia in comparison with the susceptible cultivar. Females at 30 DAI in partially resistant lines showed a delay in their development in comparison with those in the susceptible cultivar.     

Tetracyclic sulfones as potent γ-secretase inhibitors: Synthesis and structure–activity relationship studies

Complex tetracyclic sulfones were designed as γ-secretase inhibitors and a stereoselective synthesis was achieved. γ-Secretase activity was seen predominately in the (?) enantiomeric series. Compounds such as 2a and 2b showed remarkable in vitro and in vivo potency.     

Isolation of a Loma salmonae variant: biological characteristics and host range

A Salvelinus -infecting variant of Loma salmonae , derived from naturally-infected Chinook salmon Oncorhynchus tshawytscha by serial passage through brook trout Salvelinus fontinalis , has been isolated and amplified. Loma salmonae SV ( Salvelinus -variant) has a high preference for species of Salvelinus (brook trout and Arctic charr S. alpinus ) and low virulence and preference for species of Oncorhynchus (rainbow trout O. mykiss , Chinook salmon, cohoSalmon O. kisutch ) or Salmo (Atlantic salmon Salmo salar ). Although this variant of L. salmonae was different from the original, the differences do not justify describing it as a new species, although definitive determination is pending.