Mycobacterium tuberculosis inhibition of phagolysosome biogenesis and autophagy as a host defence mechanism

A marquee feature of the powerful human pathogen Mycobacterium tuberculosis is its macrophage parasitism. The intracellular survival of this microorganism rests upon its ability to arrest phagolysosome biogenesis, avoid direct cidal mechanisms in macrophages, and block efficient antigen processing and presentation. Mycobacteria prevent Rab conversion on their phagosomes and elaborate glycolipid and protein trafficking toxins that interfere with Rab effectors and regulation of specific organellar biogenesis in mammalian cells. One of the major Rab effectors affected in this process is the type III phosphatidylinositol 3-kinase hVPS34 and its enzymatic product phosphatidylinositol 3-phosphate (PI3P), a regulatory lipid earmarking organellar membranes for specific trafficking events. PI3P is also critical for the process of autophagy, recently recognized as an effector of innate and adaptive immunity. Induction of autophagy by physiological, pharmacological or immunological signals, including the major antituberculosis Th1 cytokine IFN-gamma and its downstream effector p47 GTPase LRG-47, can overcome mycobacterial phagosome maturation block and inhibit intracellular M. tuberculosis survival. This review summarizes the findings centred around the PI3P-nexus where the mycobacterial phagosome maturation block and execution stages of autophagy intersect.     

Somatic embryogenesis and transformation of the diploid <Emphasis Type="Italic">Rosa chinensis</Emphasis> cv Old Blush

Somatic embryogenesis was induced from in vitro-derived leaf explants of Rosa chinensis cultivar (cv) Old Blush. Calli producing embryos with expanded cotyledons (RcOBType1 embryos) were obtained. Further refinements of the callus maintenance medium generated a more typical rose embryogenic callus (RcOBType2) displaying high levels of secondary embryogenesis and embryos with limited cotyledon expansion Agrobacterium tumefaciens-mediated transformation assays using β-glucuronidase (GUS) reporter gene showed that both types of embryos were competent for transformation. Under selection conditions, transformed RcOBType1 explants produced non chimaeric transformed embryos, from which shoots could be adventitiously regenerated. In contrast to RcOBType1, transformed RcOBType2 embryos directly yielded transformed shoots when repeatedly cultured in selective regeneration conditions. Transformation efficiency ranged between three to nine percent and shoots suitable for rooting were obtained within 6–8 months. Transgenic plants were transferred into the greenhouse and molecularly confirmed. The availability of transformation methods in a diploid rose, R. chinensis cv. Old Blush, will be useful for gene functional studies.     

Distribution and habitat utilization in two atyid shrimps (Crustacea: Decapoda) in rivers of Nuku-Hiva Island (French Polynesia)

The distribution of Atyoida pilipes (Newport, 1847) and Caridina weberi De Man, 1892 was studied at two spatial scales on Nuku-Hiva Island (Marquesas, French Polynesia). At the stream reach scale, the two species were present at 40 and 39 sites, respectively, out of a total of 49 sites sampled. These two taxa represented more than half of the invertebrates collected at 9 sites. There was no difference in distribution between the species at the reach scale. However, clear differences appeared between the two species at the microhabitat scale. A. pilipes was more abundant in lotic habitats, even waterfalls, while C. weberi was associated with accumulations of leaves in lentic habitats. A. pilipes, particularly males, were tolerant to parameters such as water velocity, leaves, and the presence of algae and rocks. C. weberi had a more restricted altitudinal distribution and were scarce upstream from large waterfalls. These differences were linked to differences in climbing ability rather than the effect of chemical parameters, such as oxygen content. Our results suggest that little competition for space or food resources occurs between the two species. Both are feeding on small detritus particles, but through differing mechanisms and in differing habitats.