Project description:Reef-building corals live in a mutualistic relationship with photosynthetic algae (family Symbiodiniaceae) that usually provide the bulk of the energy required by the coral host. This relationship is very sensitive to temperature stress, with as little as 1°C increase above mean in sea surface temperatures (SSTs) often leading to the collapse of the association. The meta-stability of these associations has led to interest in the potential of more stress tolerant algae to supplement or substitute for the normal Symbiodiniaceae mutualists. In this respect, the apicomplexan-like microalga Chromera is of particular interest as it is considerably more temperature tolerant than are most members of the Symbiodiniaceae. Here we generated a de novo transcriptome for a Chromera strain isolated from a GBR coral (“GBR Chromera”) and compared to those of the reference strain of Chromera (“Sydney Chromera”), and to those of Symbiodiniaceae algae (Fugacium, Cladocopium and Breviolum), as well as the apicomplexan parasite, Plasmodium falciparum. By contrast with the Symbiodiniaceae, the two Chromera strains had a high level of sequence similarity evident by very low levels of divergence in orthologous genes. Although surveys of specific KEGG categories provided few general criteria by which true coral mutualists might be identified, they provide a molecular rationalization for the near ubiquitous association of Cladocopium strains with Indo-Pacific reef corals in general and with Acropora spp. in particular. In addition, HSP20 genes may underlie the higher thermal tolerance shown by Chromera compared to Symbiodiniaceae
2019-11-02 | GSE139820 | GEO
Project description:Symbiodiniaceae community of Porites cylindrica
| PRJNA873869 | ENA
Project description:Symbiodiniaceae community in Leptoria phrygia
Project description:Urea can serve as nitrogen source for coral holobionts and plays a cruscial role in coral calcification, although the degradation of urea by coral symbionts is not fully understood. In this study, we investigated the urea utilized pathway and the responses of the Symbiodiniaceae family to urea under high temperature conditions. Genome screening revealed that all Symbiodiniaceae species contain the urease (URE) and DUR2 subunit of urea amidolyase (UAD) system. However, only three speciesCladocopium goreaui, Cladopium c92, and Symbiodinium pilosum possess a complete UAD system, including both DUR1 and DUR2. Phylogentic analyses revealed that the UAD system in Symbiodiniaceae clusters more closely with symbiotic bacteria, indicating that horizontal gene transfer of UAD system has occured in coral symbionts. Physiology analysis showed that the symbiodiniacean species Cladocopium goreaui, which containing both URE and UAD, grew better under urea than ammonium conditions, as indicated by higher maximum specific growth rates. Furthermore, most genes of Symbiodiniaceae involved in urea utilization appeared to be stable under various conditions such as heat stress (HS), low light density, and nitrogen deficiency, wheras in ammonium and nitrate transporters were significantly regulated. These relatively stable molecular regulatory properties support sustained urea absorption by Symbiodiniaceae, as evidenced by an increase in δ15N2-urea absorption and the decreases in δ5N-NO3-, and δ15N-NH4+ from cultural environment to Symbiodiniaceae under HS conditions. Token together, this study reveals two distinct urea utilization systems in coral ecosystem and highlights the importance of the urea cycle in coral symbionts when facing fluctuating nitrogen environment in future warming ocean.