Sensing Environmental Stresses and Cellular Responses in Marine Algae
Assaf Vardi
Department of Plant Sciences, Weizmann Institute of Science,
P.O. Box 26, Rehovot 76100, Israel
Email: assaf.vardi@weizmann.ac.il
Marine photosynthetic microorganisms (phytoplankton) are the basis of marine foodwebs and are responsible for nearly 50% of the global annual carbon-based primary production. Despite their importance, the molecular basis for their ecological success has been largely unexplored. During bloom succession phytoplankton populations are thought to utilize chemical signals (infochemicals) to enhance their defense capacities against viruses and grazers, and to outcompete other phytoplankton for available resources. Recent advances in algal genomics and genetic and cell biology tools provide an unprecedented opportunity to elucidate the cellular mechanisms that are employed by phytoplankton during acclimation to stress in the marine environment.
In light of their unique evolutionary history, studying members of the three dominant bloom-forming algal taxa in contemporary oceans (diatoms, coccolithophores and dinoflagellates), will provide exciting insights into their unique biology and ecological success. We specifically explore the signal transduction pathways related to the origin of programmed cell death (PCD), cell-cell communication, host-virus interactions and chemical-based defense. As well as examining how these signaling pathways regulate cell fate and developmental changes as resting stage and biofilm formation.
Our recent work provides a mechanism by which cells perceive infochemicals as oxylipins and sphingolipids that derived from biotic interactions of their potential role in structuring marine microbial communities. Phytoplankton cells can utilize these secondary metabolites as part of a sophisticated surveillance system to monitor environmental stress conditions. Furthermore, these unique infochemicals can be used to develop diagnostic biomarkers to quantify biotic interactions in the ocean. Recent focus of our work is given to underline the co-evolution of host and virus around the PCD pathway and the pivotal role of chemical-based “arms race” to mediate and control these evolutionary drivers in the marine environment.
We can also foster that this novel research niche of marine chemical signaling along with recent advances in algal genomics to now provide an unprecedented opportunity for new applications in algal biofuel and isolation of marine natural products with biomedical application.
List of publications:
1. Vardi, A., Van Mooy, B.A.S., Fredericks, H.F., Popendorf K, Ossolinski J, Haramaty, L., Bidle, K.D. (2009) Viral glycosphingolipids induce lytic infection and cell death in marine phytoplankton. Science 326, 861 (2009).
2. Maumus F., Allen A., Mhiri C, Hu H., Jabbari K., Vardi A., Grandbastien MA and Bowler C. (2009) Potential impact of stress activated retrotransposons on genome evolution in a marine diatom. BMC Genomics 2009, 10:624 doi:10.1186/1471-2164-10-624.
3. Bowler, C.P., Vardi, A., Allen, A.E. (2009) Oceanographic and biogeochemical insights from diatom genomes. Annual Reviews in Marine Sciences, 2: 333-365.
4. Vardi. A, Thamatrakoln. K, Bidle. KB, Falkowski. PG (2008) Diatom genomes come of age. Genome Biology 9(12):245.
5. Vardi A (2008) Cell signaling in marine diatoms. Communicative & Integrative Biology 1(2): 134.
6. Bowler C., […], Vardi A., Grigoriev IV. (2008) The Phaeodactylum genome reveals the evolutionary history of diatom genomes. Nature doi:10.1038/nature07410.
7. Andrianasolo EH, Haramaty L, Vardi A, White E, Lutz R and Falkowski PG. (2008) Apoptosis Inducer Galactolipids from a Cultured Marine Diatom Phaeodactylum tricornutum. Journal of Natural Products DOI: 10.1021/np800124k.
8. Vardi A, Bidle KD, Kwityn C, Thompson SM, Callow JA, Falkowski PG, Bowler C (2008). A Diatom Gene Regulating Nitric Oxide Signaling and Susceptibility to Diatom-Derived Aldehydes. Current Biology DOI: 10.1016/j.cub.2008.05.037.
9. Kahl AL, Vardi A Schofield O (2008). The effect of phytoplankton physiology on export flux. Marine Ecology Progress Series (Feature Article) 354: 3-19.
10. Vardi, A., Eisenstadt, D., Murik, O., Berman-Frank, I., Zohary, T., Kaplan, A., and Levine, A. (2007). Synchronization of cell death in a dinoflagellate population is mediated by an extracreted thiol protease. Environmental Microbiology 9 (2): 360–369.
11. Montsant, A., […],Vardi, A […], Bowler, B. (2007). Insights into Diatom Cell Regulation from the Genome Sequence of Thalassiosira pseudonana. Journal of Phycology 43(3): 585-604.
12. Schatz, D., Keren, Y., Vardi, A., Sukenik, A., Carmeli, S., Börner, T., Dittmann E., and Kaplan, A. (2007). The biological role of the cyanobacterial toxins, microcystins. Environmental Microbiology 9(4), 965–970.
13. Vardi, A., Formiggini, F., Casotti, R., de Martino, A., Ribalet, F., Miralto, A., and Bowler, C. (2006). A stress surveillance system based on calcium and nitric oxide in marine diatoms. PLoS Biology 4(3):e60.
14. Allen, A.E., Vardi, A., Bowler, C.P. (2006). An ecological and evolutionary context for integrated nitrogen metabolism and cell signaling pathways in marine diatoms. Current Opinion in Plant Biology 9 (3):264-273.
15. Armbrust, E.V, […],Vardi, A., Wilkerson, F.P, and. Rokhsar D. S. (2004). The genome of the diatom Thalassiosira pseudonana: Ecology, evolution and metabolism. Science 306: 79-86.
16. Vardi, A., Schatz, D., Beeri,K., Motro, U., Sukenik, A., Levine, A., Kaplan, A.. (2002) Dinoflagellate-cyanobacterium communication may determine the composition of phytoplankton assemblage in a mesotrophic lake. Current Biology. 12: 1767-1772.
17. Sukenik, A., Eshkol, R., Livne, A., Hadas, O., Rom, M., Tchernov, D., Vardi, A., Kaplan, A. (2002). Inhibition of growth and photosynthesis of the dinoflagellate Peridinium gatunense by Microcystis sp. (cyanobacteria): A novel allelopathic mechanism. Limnology and Oceanography 47(6): 1656–1663.
18. Hadas, O., Pinkas, R., Delphine, E., Vardi, A., Kaplan, A. Sukenik, A. (1999) Limnological and ecological aspects of Aphanizomenon ovalisporum bloom in Lake Kinneret, Israel. J. Plankton Research. 21: 1439-1453.
19. Vardi, A., Berman-Frank, I., Rozenberg, T., Hadas, O., Kaplan, A., Levine, A. (1999) Programmed cell death of the bloom-forming dinoflagellate Peridinium gatunense is mediated by CO2 limitation and oxidative stress. Current Biology. 9: 1061-1064.
Highlights of scientific publications
1. Nature Chemical Biology (2006) research highlight 2(4):184.
2. Faculty of 1000 Biology http://www.f1000biology.com/article/16475869/evaluation.
3. PLoS Biology (2006) 3, e89. “Diatoms Rely on Sophisticated Signaling Systems for population Control” by Lisa Gross
4. Nature (2008) DOI: 10.1038/453583a “The Origin of Cell Death” by Nick Lane.
5. Current Biology (2008) Vol 18, R518-R519 “Diatom Signalling: Deadly Messages” by Colin Brownlee.
6. Science Signaling (2009) Vol. 2, Issue 96, p. ec362 “The Death of Cocco” by Caroline Ash.
7. Nature Reviews Microbiology 8, 6 (2010) doi:10.1038/nrmicro2285 “Viral lipid in bloom” by Andrew Jermy.
Positions: We are looking for highly-motivated graduate students and postdocs with creative thinking. A strong background in marine microbiology, molecular/cell biology or chemical ecology is advantageous. Please contact assaf.vardi@weizmann.ac.il