Host affinity of endophytic fungi and the potential for reciprocal interactions involving host secondary chemistry.

PREMISE: Interactions between fungal endophytes and their host plants present useful systems for identifying important factors affecting assembly of host-associated microbiomes. Here we investigated the role of secondary chemistry in mediating host affinity of asymptomatic foliar endophytic fungi using Psychotria spp. and Theobroma cacao (cacao) as hosts. METHODS: First, we surveyed endophytic communities in Psychotria species in a natural common garden using culture-based methods. Then we compared differences in endophytic community composition with differences in foliar secondary chemistry in the same host species, determined by liquid chromatography-tandem mass spectrometry. Finally, we tested how inoculation with live and heat-killed endophytes affected the cacao chemical profile. RESULTS: Despite sharing a common environment and source pool for endophyte spores, different Psychotria host species harbored strikingly different endophytic communities that reflected intrinsic differences in their leaf chemical profiles. In T. cacao, inoculation with live and heat-killed endophytes produced distinct cacao chemical profiles not found in uninoculated plants or pure fungal cultures, suggesting that endophytes, like pathogens, induce changes in secondary chemical profiles of their host plant. CONCLUSIONS: Collectively our results suggest at least two potential processes: (1) Plant secondary chemistry influences assembly and composition of fungal endophytic communities, and (2) host colonization by endophytes subsequently induces changes in the host chemical landscape. We propose a series of testable predictions based on the possibility that reciprocal chemical interactions are a general property of plant-endophyte interactions.

Field sampling of fig pollinator wasps across host species and host developmental phase: Implications for host recognition and specificity.

Previous genetic studies of pollinator wasps associated with a community of strangler figs (Ficus subgenus Urostigma, section Americana) in Central Panama suggest that the wasp species exhibit a range in host specificity across their host figs. To better understand factors that might contribute to this observed range of specificity, we used sticky traps to capture fig-pollinating wasp individuals at 13 Ficus species, sampling at different phases of the reproductive cycle of the host figs (e.g., trees with receptive inflorescences, or vegetative trees, bearing only leaves). We also sampled at other tree species, using them as non-Ficus controls. DNA barcoding allowed us to identify the wasps to species and therefore assign their presence and abundance to host fig species and the developmental phase of that individual tree. We found: (1) wasps were only very rarely captured at non-Ficus trees; (2) nonetheless, pollinators were captured often at vegetative individuals of some host species; (3) overwhelmingly, wasp individuals were captured at receptive host fig trees representing the fig species from which they usually emerge. Our results indicate that wasp occurrence is not random either spatially or temporally within the forest and across these hosts, and that wasp specificity is generally high, both at receptive and vegetative host trees. Therefore, in addition to studies that show chemicals produced by receptive fig inflorescences attract pollinator wasps, we suggest that other cues (e.g., chemicals produced by the leaves) can also play a role in host recognition. We discuss our results in the context of recent findings on the role of host shifts in diversification processes in the Ficus genus.

The GPI-anchored 6-Cys protein Pv12 is present in detergent-resistant microdomains of Plasmodium vivax blood stage schizonts.

Plasmodium vivax malaria remains one of the tropical diseases causing an enormous burden on global public health. Several proteins located on this parasite species' merozoite surface have been considered the most suitable antigens for being included in an anti-malarial vaccine, given the functional role they play during the parasite's interaction with red blood cells. The present study identifies and characterizes the P. vivax Pv12 surface protein which was evaluated by using molecular biology and immunochemistry assays; its antigenic potential was also examined in natural and experimental P. vivax malaria infections. The P. vivax VCG-1 strain Pv12 gene encodes a 362 amino acid-long protein exhibiting a signal peptide, a glycosylphosphatidylinositol (GPI) anchor sequence and two 6-Cys domains. The presence of the Pv12 protein on the parasite's surface and its association with detergent-resistant membrane complexes, together with its antigenic potential, supports the notion that this antigen could play an important role as a red blood cell binding ligand. Further studies aimed at establishing the immunogenicity and protection-inducing ability of the Pv12 protein or its products in the Aotus experimental model are thus suggested.