Upcoming

Our upcoming DinoSphere seminar will be on Tuesday Sept. 15th at 2 pm CEST,  featuring Ananya Kedige Rao (CNRS-CEA, France) and Rocio Ochoa Fernandez (Copenhagen University, Denmark) 

Zoom link: https://unibas.zoom.us/launch/jc/68673047674 

Meeting ID: 686 7304 7674

Passcode: 921388

From Morphology to Metabolism: A Multi-Scale View of Kleptoplasty in a Polar Dinoflagellate - Ananya Kedige Rao

Kleptoplastic protists exhibit a spectrum of retention strategies, with subtle differences in the types of organelles retained, duration of retention and possibly host control. Dinoflagellates expand on this diversity, with sequential loss and acquisition of plastids during evolution, demonstrating greater integration and evidence of horizontal gene transfer (HGT). In this work, I explore organelle retention in the polar kleptoplastidic Ross Sea Dinoflagellate (RSD) at the structural, physiological and protein levels. Nested within the Karenicaceae family, this dinoflagellate host steals plastids from its haptophyte prey, Phaeocystis antarctica, and retains them for several months. TEM and FIB-SEM 3D reconstructions show that RSD acquires not only plastids but also microalgae's nuclei and mitochondria, all of which are enclosed within a large vacuole. Upon integration into the host, the size and volume of plastids and pyrenoids increase significantly, and photosynthetic activity is enhanced. Early loss of the algal nucleus leads to a slow but gradual decline in plastid volume and photosynthesis. However, several nuclear and plastid-encoded photosystem subunits were still detected and localised within the plastid using Western Blots, Proteomics and Expansion Microscopy. Likewise, NanoSIMS isotope mapping revealed that carbon fixation and transfer were also maintained after >2 months. More intriguingly, the stolen algal mitochondria were retained for several months, maintaining close interactions with plastids and highlighting possible organelle crosstalk that supports plastid maintenance. At present, pushing the scale further, I am involved in ongoing experiments on RSD (with preliminary results) led by my team members, including feeding and prey specificity, environmental adaptation, and cryo-ET imaging to resolve fine-scale plastid architecture.

Engineering dinoflagellate carotenoid pathways in plants - Rocio Ochoa Fernandez  

 Microalgae contribute to approximately 50% of global CO2 fixation through photosynthesis. Carotenoids play a crucial role in photosynthesis by assisting in light harvesting and providing photoprotection. Dinoflagellates that live in symbiosis with corals have unique carotenoids such as peridinin that enhance the light-harvesting capacity of microalgae in this unique marine ecosystem. However, the enzymatic pathways for the biosynthesis of these carotenoids are not fully elucidated.

Our research focuses on characterizing candidate algae carotenoid biosynthetic genes in the plant Nicotiana benthamiana and expressing them in the evolutionarily related alga Nannochloropsis oceanica. We utilize LC-MS to study changes in pigment composition upon expression of dinoflagellate carotenoid candidate genes. We furthermore have identified a two-domain enzyme substantially increases the precursors for peridinin. We are currently implementing this gene into our transient expression plant system using Nicotiana benthamiana and using it as a tool to have an algal-like carotenoid profile in plants. This platform will allow us in the future to screen and characterize other carotenoid related genes, potentially generating plants with dinoflagellate carotenoids for improved light harvesting leading to higher crop yields.