Molecular Mechanisms Of The Interaction Between Phaeodactylum Tricornutum And Alexandrium Tamarense

The succession of dominant phytoplankton communities plays an important roleduring the harmful algae bloom (HAB). However, the molecular mechanism of theecological succession remains unclear, such as the most commonly occurred successionof diatoms and dinoflagellates. Hence, we investigated the molecular responses of adiatom Phaeodactylum tricornutum during the co-cultivation with a dinoflagellateAlexandrium tamarense in combination with biochemical and molecular approaches.The growth of P. tricornutum was significantly inhibited within24h of co-cultivation.The organelles such as the chloroplast and mitochondrion in P. tricornutum wereseverely damaged, including the blurring or disintegration of membrane and thedeformation of organelles. Transcriptional changes of P. tricornutum after co-cultivationwere analyzed by RNA-sequence. Transcription levels of genes involved in glycolysis,TCA cycle, fatty acid β-oxidation and oxidation phosphorylation were downregulated,similar to the carbon fixation and photosynthesis, indicating that the capabilities ofenergy metabolism and uptake of carbon dioxide were inhibited. And several proteinsassociated with check points and cell cycle were also downregulated, suggesting theoccurrence of the suppression of DNA replication and cell division. Moreover,upregulation of ABCB1transporter implicated that certain allelochemicals could bereleased from A. tamarense and played a role in the interaction between diatoms anddinoflagellates. Furthermore, a predicted leucine-rich repeat receptor-like kinaseflagellin-sensitive2(FLS2) was also dramatically upregulated, indicating anotherpathway involved in the interaction different from the allelopathy. Our results shed lighton the molecular mechanisms of the interaction between diatoms and dinoflagellates,thus contributing to the explanation of the succession of phytoplankton communitiesduring HAB.