Devil inside: does plant programmed cell death involve the endomembrane system?

Eukaryotic cells have to constantly cope with environmental cues and integrate developmental signals. Cell survival or death is the only possible outcome. In the field of animal biology, tremendous efforts have been put into the understanding of mechanisms underlying cell fate decision. Distinct organelles have been proven to sense a broad range of stimuli and, if necessary, engage cell death signalling pathway(s). Over the years, forward and reverse genetic screens have uncovered numerous regulators of programmed cell death (PCD) in plants. However, to date, molecular networks are far from being deciphered and, apart from the autophagic compartment, no organelles have been assigned a clear role in the regulation of cellular suicide. The endomembrane system (ES) seems, nevertheless, to harbour a significant number of cell death mediators. In this review, the involvement of this system in the control of plant PCD is discussed in‐depth, as well as compared and contrasted with what is known in animal and yeast systems.     

Phylogeography of two parthenogenetic sawfly species (Hymenoptera: Tenthredinidae): relationship of population genetic differentiation to host plant distribution

This study compares the population genetic structure of two obligate parthenogenetic sawfly species, Aneugmenus padi (L.) Zhelochovtsev and Eurhadinoceraea ventralis (Panzer) Enslin (Hymenoptera: Tenthredinidae). Allozymes were used to detect genetic differences in larvae collected at different sites in six European countries. For A. padi , scoring six polymorphic enzymes revealed the existence of five dominant, widely distributed clones and several more with only very few individuals occurring locally. The clonal diversity and identity differed across collection sites, with up to at maximum eight clones coexisting at a single locality. In contrast, in E. ventralis , individuals from different localities were all monomorphic for at least six different enzymes and are therefore assumed to belong to the same clone. Differences in population genetic structure of these sawfly species can be related to the differing distributions of their host plants: the fern, Pteridium aquilinum , the host of A. padi , has been an invasive species for more than two hundred years. Spread of clones of A. padi is likely to have closely followed the complex invasive pattern of spread of the plant. Larvae of E. ventralis were collected from local, horticultural plantings of Clematis spp. of recent origin probably with gardeners having traded plants infested with the sawfly.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 219–227.     

Soils,a sink for N2O? A review

Soils are the main sources of the greenhouse gas nitrous oxide (N₂O). The N₂O emission at the soil surface is the result of production and consumption processes. So far, research has concentrated on net N₂O production. However, in the literature, there are numerous reports of net negative fluxes of N₂O, (i.e. fluxes from the atmosphere to the soil). Such fluxes are frequent and substantial and cannot simply be dismissed as experimental noise.
Net N₂O consumption has been measured under various conditions from the tropics to temperate areas, in natural and agricultural systems. Low mineral N and large moisture contents have sometimes been found to favour N₂O consumption. This fits in with denitrification as the responsible process, reducing N₂O to N₂. However, it has also been reported that nitrifiers consume N₂O in nitrifier denitrification. A contribution of various processes could explain the wide range of conditions found to allow N₂O consumption, ranging from low to high temperatures, wet to dry soils, and fertilized to unfertilized plots. Generally, conditions interfering with N₂O diffusion in the soil seem to enhance N₂O consumption. However, the factors regulating N₂O consumption are not yet well understood and merit further study.
Frequent literature reports of net N₂O consumption suggest that a soil sink could help account for the current imbalance in estimated global budgets of N₂O. Therefore, a systematic investigation into N₂O consumption is necessary. This should concentrate on the organisms, reactions, and environmental factors involved.     

Evolution of the concepts of vitellogenesis in Polychaete Annelids

Summary

In polychaete annelids, two types of vitellogenesis have been described: a heterosynthetic mechanism (in a number of different of worms) and an autosynthetic process (other including Nereis). Recent biochemical results suggest that the heterosynthetic mechanism is more general than previously thought. In Nereis, the vitellogenin (the precursor) is synthesized in coelomocytes and after transfer through coelomic fluid incorporated into oocytes. In germinal cells, a conversion process, involving proteolytic cleavages of vitellogenin, produces mature vitellins which are accumulated in yolk granules.

The neurohormones identified so far are not essential for vitellogenin synthesis. It is possible that these neurohormones regutate enzymatic activities in the oocytes.     

Multilocus Genotyping of Pneumocystis jirovecii in Patients Developing Diverse Forms of Parasitism: Implication for a Wide Human Reservoir for the Fungus

ABSTRACT. Pneumocystis jirovecii ITS and DHPS genotypes were identified in 3 patient groups developing diverse forms of P. jirovecii infections: 13 patients with Pneumocystis pneumonia, 8 patients merely colonized by the fungus, and 19 immunocompetent infants with bronchiolitis developing mild P. jirovecii infection. Common P. jirovecii genotypes were found in the 3 patient groups, suggesting that common sources of P. jirovecii were involved in the fungus acquisition, and that transmission cycles of P. jirovecii infections in these patient groups are not independent. Parasitized patients, whatever the form of parasitism they present, may he part of a common reservoir for P. jirovecii.     

Male–female associations and female olfactory neurogenesis with pair bonding in Mus spicilegus

Mound‐building mice Mus spicilegus exhibit life‐history traits that are unique among the Mus species complex, such as the cooperative mound‐building behaviour that gives the species its common name. In this and other socially coordinated activities, such as those associated with reproduction, these mice should be able to recognize individuals (via discrimination based on kinship, population and species) to mediate their interactions. Our previous studies have provided evidence of population and species recognition in M. spicilegus. The aims of the present study were: (i) to study associations of mice during their reproductive period (in outdoor enclosures), (ii) to investigate whether there is an influence of relatedness of females in these associations, (iii) to determine whether female M. spicilegus are able to make kin vs. non‐kin discriminations, and (iv) to study certain neurobiological correlates of male–female bonds. Stable male–female associations were found in almost all the experimental groups, both those with unrelated and unfamiliar females and those with unfamiliar sisters. Kinship between females did not affect female associations in our enclosure experiment, but in our kin discrimination experiment females did distinguish between unfamiliar sisters and unfamiliar unrelated females. Shared kinship may not encourage cooperative rearing of pups but could enhance cooperation in building mounds where mice over‐winter. Male–female associations could be based on a social bond, as hypothesized from previous laboratory experiments. This was substantiated in this study by increased olfactory bulbar neurogenesis in females that preferred (in two choice tests) their sexual partner 3 weeks after their first mating. Based on these results there is clear evidence to suggest that the mating system of M. spicilegus is social monogamy. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84 , 323–334.