Project description:Coral reefs are based on the symbiotic relationship between corals and photosynthetic dinoflagellates of the genus Symbiodinium. We followed gene expression of coral larvae of Acropora palmata and Montastraea faveolata after exposure to Symbiodinium strains that differed in their ability to establish symbioses. We show that the coral host transcriptome remains almost unchanged during infection by competent symbionts, but is massively altered by symbionts that fail to establish symbioses. Our data suggest that successful coral-algal symbioses depend mainly on the symbionts' ability to enter the host in a stealth manner rather than a more active response from the coral host.
Project description:Animal-algal photosymbioses are a unique group of symbiotic relationships in which animals harbor photosynthetic algae within their cells and tissues. Both marine and freshwater sponges host algal endosymbionts. In previous work, we demonstrated that freshwater sponges can acquire these endosymbionts horizontally through algal infection and that potentially conserved evolutionary pathways may lead to the establishment of the endosymbioses including those involved in endocytosis, ion transport, vesicle-mediated transport, innate immunity, redox regulation, and metabolic processes. Here, we show that algal symbionts can be transferred vertically from algal-bearing overwintering gemmules to adult sponges, and that their proliferation is enhanced by light. Sponges grown under light conditions harbored higher algal loads than those in the dark; however, algae were still able to proliferate and persist in sponges reared in the dark, occupying similar spatial locations to those grown in light. RNA-Seq analysis of algal-bearing sponges across developmental stages in light and dark conditions revealed genetic regulatory pathways involved in the transmission and establishment of the endosymbiosis. Differential expression analysis indicated that the endocytosis and SNARE pathways regulate the internalization and transport of algae at the earliest stage of hatching under light conditions and later in development under dark conditions, potentially contributing to the recruitment of endosymbiotic algae. In sponges hatched in the dark, genes involved in vesicle acidification are regulated, alongside changes in the expression of genes in the pentose phosphate pathway - a key metabolic route involved in redox homeostasis and circadian rhythm regulation via NADPH metabolism, is observed. E. muelleri serves as a versatile model system, supported by robust genomic and transcriptomic resources, for studying host-symbiont interactions. It offers a unique opportunity to investigate the molecular signaling and environmental factors that shape symbiosis in a system where the host can exist with or without algal endosymbionts, symbionts can be acquired either horizontally or vertically, and proliferation of the algae can occur with or without photosynthesis.
Project description:gene expression profiling in different zones along the gradient of the growing maize leaf balde aover a time course of dirunal cycle and carbon starvation by extension of the night Plants assimilate carbon in their photosynthetic tissues in the light. However, carbon is required during the night, and in non-photosynthetic organs. It is therefore essential that plants manage their carbon resources spatially and temporally and coordinate growth with carbon availability. In growing maize (Zea mays) leaf blades a defined developmental gradient facilitates analyses in the cell division, elongation and mature zones. We investigated the responses of the metabolome and transcriptome and polysome loading, as a qualitative proxy for protein synthesis, at dusk, dawn and 6, 14 and 24 hours into an extended night, and tracked whole leaf elongation over this time course. Starch and sugars are depleted by dawn in the mature zone, but only after an extension of the night in the elongation and division zones. Sucrose recovers partially between 14 and 24 h into the extended night in the growth zones but not the mature zone. The global metabolome and transcriptome track these zone-specific changes in sucrose. Leaf elongation and polysome loading in the growth zones also remain high at dawn, decrease between 6 and 14 h into the extended night and then partially recover indicating that growth processes are determined by local carbon status. The level of sucrose-signaling metabolite trehalose-6-phosphate, and the trehalose-6-phosphate:sucrose ratio are much higher in growth than mature zones at dusk and dawn but fall in the extended night. Candidate genes were identified by searching for transcripts that show characteristic temporal response patterns or contrasting responses to carbon starvation in growth and mature zones.