Progressive and controlled development of mouse dendritic cells from Flt3+ CD11b+ progenitors in vitro

Dendritic cells (DC) represent key regulators of the immune system, yet their development from nemopoietic precursors is poorly defined. In this study, we describe an in vitro system for amplification of a Flt3+CD11b + progenitor from mouse bone marrow with specific cytokines. Such progenitor cells develop into both CD11b+ and CD11b- DC, and CD8α+ and CD8α+ DC in vivo. Furthermore, with GM-CSF, these progenitors synchronously differentiated into fully functional DC in vitro. This two-step culture system yields homogeneous populations of Flt3+CD11b+ progenitor cells in high numbers and allows monitoring the consecutive steps of DC development in vitro under well-defined conditions. We used phenotypic and functional markers and transcriptional profiling by DNA microarrays to study the Flt3 +CD11b+ progenitor and differentiated DC. We report here on an extensive analysis of the surface Ag expression of Flt3 +CD11b+ progenitor cells and relate that to surface Ag expression of hemopoietic stem cells. Flt3+CD11b+ progenitors studied exhibit a broad overlap of surface Ags with stem cells and express several stem cell Ags such as Flt3, IL-6R, c-kit/SCF receptor, and CD93/AA4.1, CD133/AC133, and CD49f/Integrin α6. Thus, Flt3 +CD11b+ progenitors express several stem cell surface Ags and develop into both CD11b+ and CD11b- DC, and CD8α + and CD8α- DC in vivo, and thus into both of the main conventional DC subtypes

Correlations between physical and chemical defences in plants: tradeoffs, syndromes, or just many different ways to skin a herbivorous cat?

� Most plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. � We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences. � Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species’ overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes. � Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species

Morphological trait matching shapes plant-frugivore networks across the Andes

Interactions between resource and consumer species are organized in ecological networks. Species interactions in these networks are influenced by the functional traits of the interacting partners, but the generality of trait‐based interaction rules and the relationship between functional traits and a species’ specialization on specific interaction partners are not yet understood. Here we combine data on eight interaction networks between fleshy‐fruited plants and frugivorous birds sampled across the tropical and subtropical Andean range. We test which combinations of morphological plant and animal traits determine trait matching between resource and consumer species in these networks. In addition, we test which of the morphological traits influence functional specialization of plant and bird species. In a meta‐analysis across network‐specific fourth‐corner analyses, we found that plant–animal trait pairs related to size matching (fruit size–beak size) and avian foraging behavior (plant height–wing shape and crop mass–body mass) were positively related in these networks. The degree of functional specialization on specific interaction partners was positively related to crop mass in plants and to the pointedness of the wing in birds. Our findings show that morphological trait matching between fleshy‐fruited plants and frugivorous birds is a general phenomenon in plant–frugivore networks across the Andes and that specific plant and bird traits can be used to approximate the degree of functional specialization. These insights into the generality of interaction rules are the base for predictions of species interactions in ecological networks, for instance in novel communities in the future, and can be applied to identify plant and animal species that fulfill specialized functional roles in ecological communities