Symbiodinium transcriptome and global responses of cells to immediate changes in light intensity when grown under autotrophic or mixotrophic conditions

Tingting Xiang*, William Nelson, Jesse Rodriguez, Dimitri Tolleter, Arthur R. Grossman

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    67 Citations (Scopus)

    Abstract

    Symbiosis between unicellular dinoflagellates (genus Symbiodinium) and their cnidarian hosts (e.g. corals, sea anemones) is the foundation of coral reef ecosystems. Dysfunction of this symbiosis under changing environmental conditions has led to global reef decline. Little information is known about Symbiodinium gene expression and mechanisms by which light impacts host-symbiont associations. To address these issues, we generated a transcriptome from axenic Symbiodinium strain SSB01. Here we report features of the transcriptome, including occurrence and length distribution of spliced leader sequences, the functional landscape of encoded proteins and the impact of light on gene expression. Expression of many Symbiodinium genes appears to be significantly impacted by light. Transcript encoding cryptochrome 2 declined in high light while some transcripts for Regulators of Chromatin Condensation (RCC1) declined in the dark. We also identified a transcript encoding a light harvesting AcpPC protein with homology to Chlamydomonas LHCSR2. The level of this transcript increased in high light autotrophic conditions, suggesting that it is involved in photo-protection and the dissipation of excess absorbed light energy. The most extensive changes in transcript abundances occurred when the algae were transferred from low light to darkness. Interestingly, transcripts encoding several cell adhesion proteins rapidly declined following movement of cultures to the dark, which correlated with a dramatic change in cell surface morphology, likely reflecting the complexity of the extracellular matrix. Thus, light-sensitive cell adhesion proteins may play a role in establishing surface architecture, which may in turn alter interactions between the endosymbiont and its host. Significance Statement Survival of reef ecosystems requires mutualism between coral animals and their intracellular algae - dinoflagellates in the genus Symbiodinium. This symbiotic lifestyle is deteriorating globally due to environmental stressors. Therefore, it is critical to learn more about dinoflagellates and their cnidarian hosts. We investigated responses of axenic Symbiodinium strain SSB01 to light at the physiological, transcriptional and cellular levels, and discuss how the results may link to the characteristics of these alga and coral bleaching.

    Original languageEnglish
    Pages (from-to)67-80
    Number of pages14
    JournalPlant Journal
    Volume82
    Issue number1
    DOIs
    Publication statusPublished - 1 Apr 2015

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