The cost of ant attendance and melezitose secretion in the black bean aphid Aphis fabae

1. The aphid Aphis fabae (Scopoli) is facultatively tended by Lasius niger (Linnaeus) ants. Previously, we found that A. fabae colonies can be made up of several clones, and that clones display significant differences in the composition of their honeydew sugars, especially in the amount of the ant attractant sugar melezitose that they produce. 2. These clonal differences could greatly impact the strength of the mutualistic interaction with ants as well as the aphids' fitness. 3. Hence, the aim of this study was to compare the fitness of different A. fabae clones that differed in their melezitose secretion, and whether or not they were tended by ants. 4. Individual fitness indices, colony growth, and alate production of single‐clone aphid colonies were analysed. 5. The results demonstrate that the fitness consequences of ant attendance critically depend on an interaction between levels of melezitose production. In particular, we show that high‐melezitose secreting clones produce fewer alates and hence might have a lower dispersal ability in the presence of ants. 6. Furthermore, these data confirm previous evidence that ant attendance is costly and results in the production of fewer apterae.     

Screening and secretomic analysis of enthomopatogenic Beauveria bassiana isolates in response to cowpea weevil (Callosobruchus maculatus) exoskeleton

The production of cowpea (Vigna unguiculata), an important self-sustained crop in Latin America and Africa, is severely affected by damage by the cowpea weevil Callosobruchus maculatus. The presence of a single larva in stored seeds can lead to losses of almost 40%. Control of C. maculatus currently relies on the inefficient use of chemical insecticides and post-harvest treatments. The use of entomopathogenic fungus became a reliable alternative for coleopteran pest control and has been extensively investigated. Among them, Beauveria bassiana and Metarhizium anisopliae were widely evaluated in order to measure their virulence toward many insects. In this report, we evaluated the insecticidal activity of ten strains of B. bassiana and the most lethal fungi strains were analyzed for proteinaceous secretions by two dimensional electrophoresis and for enzyme activities, including chitinolytic, proteolytic and alpha-amylolytic activities. This study could, in the near future, help to establish novel biotechnological tools to use for cowpea weevil control.     

PER-TIM interactions with the photoreceptor cryptochrome mediate circadian temperature responses in Drosophila

Drosophila cryptochrome (CRY) is a key circadian photoreceptor that interacts with the period and timeless proteins (PER and TIM) in a light-dependent manner. We show here that a heat pulse also mediates this interaction, and heat-induced phase shifts are severely reduced in the cryptochrome loss-of-function mutant cry^b. The period mutant per^L manifests a comparable CRY dependence and dramatically enhanced temperature sensitivity of biochemical interactions and behavioral phase shifting. Remarkably, CRY is also critical for most of the abnormal temperature compensation of per^L flies, because a per^L; cry^b strain manifests nearly normal temperature compensation. Finally, light and temperature act together to affect rhythms in wild-type flies. The results indicate a role for CRY in circadian temperature as well as light regulation and suggest that these two features of the external 24-h cycle normally act together to dictate circadian phase.     

Horizontal transmission of begomoviruses between Bemisia tabaci biotypes

We have previously shown that the monopartite Tomato yellow leaf curl virus (TYLCV), a begomovirus (family Geminiviridae, genus Begomovirus) infecting tomato plants can be transmitted in a gender-dependent manner among its insect vector the whitefly Bemisia tabaci type B (Gennaduis) (Aleyrodidae: Hemiptera) during mating. Viruliferous females were able to transmit the virus to non-viruliferous males and vice versa, in the absence of any other virus source. The recipient insects were able to infect tomato plants. In this communication, we present evidence that two bipartite begomoviruses infecting cucurbits, Squash leaf curl virus (SLCV) and Watermelon chlorotic stunt virus (WmCSV) can be transmitted in a gender-dependent manner among whiteflies. In addition we show that TYLCV can be transmitted during mating among individuals from the same biotype (from B-males to B-females and vice versa; and from Q-males to Q-females and vice versa). However, viruliferous males of the B biotype are unable to transmit the virus to females of the Q biotype (and vice versa); similarly, viruliferous males of the Q biotype are unable to transmit the virus to females of the B biotype (and vice versa). These findings support the hypothesis that a pre-zygotic mating barrier between the Q and B biotypes is the cause for the absence of gene flow between the two biotypes, and that virus transmission can be used as a marker for inter-biotype mating. To be transmitted during mating, the virus needs to be present in the haemolymph of the donor insect. Abutilon mosaic virus (AbMV), a bipartite begomovirus that can be ingested but not transmitted by B. tabaci, is absent in the whitefly haemolymph, and cannot be transmitted during mating. Mating was a precondition for horizontal virus transfer from male to female, or female to male. Virus was not transmitted when viruliferous B. tabaci were caged with the non-vector non-viruliferous whitefly Trialeurodes vaporariorum (Westwood) (Aleyrodidae: Hemiptera) and vice versa.     

Analysis of bronchoalveolar lavage fluid proteome from systemic sclerosis patients with or without functional, clinical and radiological signs of lung fibrosis

Lung fibrosis is a major cause of mortality and morbidity in systemic sclerosis (SSc). However, its pathogenesis still needs to be elucidated. We examined whether the alteration of certain proteins in bronchoalveolar lavage fluid (BALF) might have a protective or a causative role in the lung fibrogenesis process. For this purpose we compared the BALF protein profile obtained from nine SSc patients with lung fibrosis (SSc_Fib+) with that obtained from six SSc patients without pulmonary fibrosis (SSc_Fib-) by two-dimensional gel electrophoresis (2-DE). Only spots and spot-trains that were consistently expressed in a different way in the two study groups were taken into consideration. In total, 47 spots and spot-trains, corresponding to 30 previously identified proteins in human BALF, showed no significant variation between SSc_Fib+ patients and SSc_Fib- patients, whereas 24 spots showed a reproducible significant variation in the two study groups. These latter spots corresponded to 11 proteins or protein fragments, including serum albumin fragments (13 spots), 5 previously recognized proteins (7 spots), and 4 proteins (3 spots) that had not been previously described in human BALF maps, namely calumenin, cytohesin-2, cystatin SN, and mitochondrial DNA topoisomerase 1 (mtDNA TOP1). Mass analysis did not determine one protein-spot. The two study groups revealed a significant difference in BALF protein composition. Whereas levels of glutathione S-transferase P (GSTP), Cu–Zn superoxide dismutase (SOD) and cystatin SN were downregulated in SSc_Fib+ patients compared with SSc_Fib- patients, we observed a significant upregulation of α1-acid glycoprotein, haptoglobin-α chain, calgranulin (Cal) B, cytohesin-2, calumenin, and mtDNA TOP1 in SSc_Fib+ patients. Some of these proteins (GSTP, Cu–Zn SOD, and cystatin SN) seem to be involved in mechanisms that protect lungs against injury or inflammation, whereas others (Cal B, cytohesin-2, and calumenin) seem to be involved in mechanisms that drive lung fibrogenesis. Even if the 2-DE analysis of BALF did not provide an exhaustive identification of all BALF proteins, especially those of low molecular mass, it allows the identification of proteins that might have a role in lung fibrogenesis. Further longitudinal studies on larger cohorts of patients will be necessary to assess their usefulness as predictive markers of disease.     

The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

Background

Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping.

Results

Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X₁, X₂, X₃, X₅, and in chromosome Y₁.

Conclusion

Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain, with the final additions after platypus and echidna divergence. Genome sequencing and contig anchoring show no homology yet between platypus and therian Xs; thus, monotremes have a unique XY sex chromosome system that shares some homology with the avian Z.