Comparative internal structure of dorsal lips and radiolar appendages in sabellidae (Polychaeta) and phylogenetic implications

Fan worms (Sabellidae) possess paired modified prostomial structures at the base of the radiolar crown, dorso‐lateral to the mouth, called dorsal lips. The dorsal lips are involved in the sorting of particles collected by the radiolar crown. The range of variation in the morphology of dorsal lips is extensive, and probably this is not only due to adaptations to different environments and feeding preferences but also due to phylogenetic constraints. In this study, we describe and compare the morphology of dorsal lips in a range of sabellid taxa based on histological cross‐sections of these structures, and compare our data and terminology with those of previous studies. Dorsal lips are maintained erect in most taxa by a modified radiole fused to them known as dorsal radiolar appendage. We suggest that dorsal radiolar appendages with an internal supporting axis (cellular or acellular) and probably also the ventral lips are synapomorphies of the family. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

A Dated Phylogeny Complements Macroecological Analysis to Explain the Diversity Patterns in Geonoma (Arecaceae)

Integrating phylogenetic data into macroecological studies of biodiversity patterns may complement the information provided by present‐day spatial patterns. In the present study, we used range map data for all Geonoma (Arecaceae) species to assess whether Geonoma species composition forms spatially coherent floristic clusters. We then evaluated the extent to which the spatial variation in species composition reflects present‐day environmental variation vs. nonenvironmental spatial effects, as expected if the pattern reflects historical biogeography. We also examined the degree of geographic structure in the Geonoma phylogeny. Finally, we used a dated phylogeny to assess whether species richness within the floristic clusters was constrained by a specific historical biogeographic driver, namely time‐for‐diversification. A cluster analysis identified six spatially coherent floristic clusters, four of which were used to reveal a significant geographic phylogenetic structure. Variation partitioning analysis showed that 56 percent of the variation in species composition could be explained by spatial variables alone, consistent with historical factors having played a major role in generating the Geonoma diversity pattern. To test for a time‐for‐diversification effect, we correlated four different species richness measures with the diversification time of the earliest large lineage that is characteristic of each cluster. In support of this hypothesis, we found that geographic areas with higher richness contained older radiations. We conclude that current geographic diversity patterns in Geonoma reflect the present‐day climate, but to a larger extent are related to nonenvironmental spatial constraints linked to colonization time, dispersal limitation, and geological history, followed by within‐area evolutionary diversification. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

Spindle assembly defects leading to the formation of a monopolar mitotic apparatus

Mitotic spindle formation in animal cells involves microtubule nucleation from two centrosomes that are positioned at opposite sides of the nucleus. Microtubules are captured by the kinetochores and stabilized. In addition, microtubules can be nucleated independently of the centrosome and stabilized by a gradient of Ran—GTP, surrounding the mitotic chromatin. Complex regulation ensures the formation of a bipolar apparatus, involving motor proteins and controlled polymerization and depolymerization of microtubule ends. The bipolar apparatus is, in turn, responsible for faithful chromosome segregation. During recent years, a variety of experiments has indicated that defects in specific motor proteins, centrosome proteins, kinases and other proteins can induce the assembly of aberrant spindles with a monopolar morphology or with poorly separated poles. Induction of monopolar spindles may be a useful strategy for cancer therapy, since ensuing aberrant mitotic exit will usually lead to cell death. In this review, we will discuss the various underlying molecular mechanisms that may be responsible for monopolar spindle formation.     

The formation of titan cells in Cryptococcus neoformans depends on the mouse strain and correlates with induction of Th2‐type responses

Cryptococcus neoformans is a pathogenic yeast that can form titan cells in the lungs, which are fungal cells of abnormal enlarged size. Little is known about the factors that trigger titan cells. In particular, it is not known how the host environment influences this transition. In this work, we describe the formation of titan cells in two mouse strains, CD1 and C57BL/6J. We found that the proportion of C. neoformans titan cells was significantly higher in C57BL/6J mice than in CD1. This higher proportion of titan cells was associated with a higher dissemination of the yeasts to the brain. Histology sections demonstrated eosinophilia in infected animals, although it was significantly lower in the CD1 mice which presented infiltration of lymphocytes. Both mouse strains presented infiltration of granulocytes, but the amount of eosinophils was higher in C57BL/6J. CD1 mice showed a significant accumulation of IFN‐γ, TNF‐α and IL17, while C57BL/BL mice had an increase in the anti‐inflammatory cytokine IL‐4. IgM antibodies to the polysaccharide capsule and total IgE were more abundant in the sera from C57BL/6J, confirming that these animals present a Th2‐type response. We conclude that titan cell formation in C. neoformans depends, not only on microbe factors, but also on the host environment.     

SD-RLK28 positively regulates pollen hydration on stigmas as a PCP-Bβ receptor in Arabidopsis thaliana

Pollen hydration on dry stigmas is strictly regulated by pollen–stigma interactions in Brassicaceae. Although several related molecular events have been described, the molecular mechanism underlying pollen hydration remains elusive. Multiple B-class pollen coat proteins(PCP-Bs) are involved in pollen hydration. Here, by analyzing the interactions of two PCP-Bs with three Arabidopsis thaliana stigmas strongly expressing S-domain receptor kinase(SD-RLK), we determined that SD-RLK28 directly intera...