Molecular mechanisms of acclimation to long-term elevated temperature exposure in marine symbioses.

Seawater temperature rise in French Polynesia has repeatedly resulted in the bleaching of corals and giant clams. Because giant clams possess distinctive ectosymbiotic features, they represent a unique and powerful model for comparing molecular pathways involved in (a) maintenance of symbiosis and (b) acquisition of thermotolerance among coral reef organisms. Herein, we explored the physiological and transcriptomic responses of the clam hosts and their photosynthetically active symbionts over a 65 day experiment in which clams were exposed to either normal or environmentally relevant elevated seawater temperatures.

Transcriptomic analysis reveals protein homeostasis breakdown in the coral Acropora millepora during hypo-saline stress.

Background: Coral reefs can experience salinity fluctuations due to rainfall and runoff; these events can have major impacts on the corals and lead to bleaching and mortality. On the Great Barrier Reef (GBR), low salinity events, which occur during summer seasons and can involve salinity dropping ~ 10 PSU correlate with declines in coral cover, and these events are predicted to increase in frequency and severity under future climate change scenarios. In other marine invertebrates, exposure to low salinity causes increased expression of genes involved in proteolysis, responses to oxidative stress, and membrane transport, but the effects that changes in salinity have on corals have so far received only limited attention.

Erratum: Publisher Correction: genomes reveal adaptive evolution of functions related to coral-dinoflagellate symbiosis.

[This corrects the article DOI: 10.1038/s42003-018-0098-3.].

genomes reveal adaptive evolution of functions related to coral-dinoflagellate symbiosis.

Symbiosis between dinoflagellates of the genus and reef-building corals forms the trophic foundation of the world's coral reef ecosystems. Here we present the first draft genome of (Clade C, type C1: 1.03 Gbp), one of the most ubiquitous endosymbionts associated with corals, and an improved draft genome of (Clade F, strain CS-156: 1.

Transcriptomic analysis of the response of Acropora millepora to hypo-osmotic stress provides insights into DMSP biosynthesis by corals.

Background: Dimethylsulfoniopropionate (DMSP) is a small sulphur compound which is produced in prodigious amounts in the oceans and plays a pivotal role in the marine sulfur cycle. Until recently, DMSP was believed to be synthesized exclusively by photosynthetic organisms; however we now know that corals and specific bacteria can also produce this compound. Corals are major sources of DMSP, but the molecular basis for its biosynthesis is unknown in these organisms.

Trm112p is a 15-kDa zinc finger protein essential for the activity of two tRNA and one protein methyltransferases in yeast.

The degenerate base at position 34 of the tRNA anticodon is the target of numerous modification enzymes. In Saccharomyces cerevisiae, five tRNAs exhibit a complex modification of uridine 34 (mcm(5)U(34) and mcm(5)s(2)U(34)), the formation of which requires at least 25 different proteins. The addition of the last methyl group is catalyzed by the methyltransferase Trm9p.

The NRAMP6 metal transporter contributes to cadmium toxicity.

NRAMP (natural resistance-associated macrophage protein) homologues are evolutionarily conserved bivalent metal transporters. In Arabidopsis, AtNRAMP3 and AtNRAMP4 play a key role in iron nutrition of the germinating plantlet by remobilizing vacuolar iron stores. In the present paper we describe the molecular and physiological characterization of AtNRAMP6.

Trm11p and Trm112p are both required for the formation of 2-methylguanosine at position 10 in yeast tRNA.

N(2)-Monomethylguanosine-10 (m(2)G10) and N(2),N(2)-dimethylguanosine-26 (m(2)(2)G26) are the only two guanosine modifications that have been detected in tRNA from nearly all archaea and eukaryotes but not in bacteria. In Saccharomyces cerevisiae, formation of m(2)(2)G26 is catalyzed by Trm1p, and we report here the identification of the enzymatic activity that catalyzes the formation of m(2)G10 in yeast tRNA. It is composed of at least two subunits that are associated in vivo: Trm11p (Yol124c), which is the catalytic subunit, and Trm112p (Ynr046w), a putative zinc-binding protein.

Spb1p-directed formation of Gm2922 in the ribosome catalytic center occurs at a late processing stage.

rRNA molecules undergo extensive posttranscriptional modification, predominantly 2'-O-ribose methylation and pseudouridine formation, both of which are guided by the numerous small nucleolar RNAs in eukaryotes. Here, we describe an exception to this rule. The essential yeast nucleolar protein Spb1p is a site-specific rRNA methyltransferase modifying the universally conserved G2922 that is located within the A loop of the catalytic center of the ribosome.

mRNA decay is rapidly induced after spore germination of Saccharomyces cerevisiae.

Spores from the yeast Saccharomyces cerevisiae can germinate and resume their vegetative growth when placed in favorable conditions. Biochemical studies on germination have been limited by the difficulty of obtaining a pure population of spores germinating synchronously. Here, we report that spores can be purified and sorted according to their size by centrifugal elutriation and that these spores are able to germinate synchronously.

Trm7p catalyses the formation of two 2'-O-methylriboses in yeast tRNA anticodon loop.

The genome of Saccharomyces cerevisiae encodes three close homologues of the Escherichia coli 2'-O-rRNA methyltransferase FtsJ/RrmJ, designated Trm7p, Spb1p and Mrm2p. We present evidence that Trm7p methylates the 2'-O-ribose of nucleotides at positions 32 and 34 of the tRNA anticodon loop, both in vivo and in vitro. In a trm7Delta strain, which is viable but grows slowly, translation is impaired, thus indicating that these tRNA modifications could be important for translation efficiency.

MRM2 encodes a novel yeast mitochondrial 21S rRNA methyltransferase.

Mitochondria of the yeast Saccharomyces cerevisiae assemble their ribosomes from ribosomal proteins, encoded by the nuclear genome (with one exception), and rRNAs of 15S and 21S, encoded by the mitochondrial genome. Unlike cytoplasmic rRNA, which is highly modified, mitochondrial rRNA contains only three modified nucleotides: a pseudouridine (Psi(2918)) and two 2'-O-methylated riboses (Gm(2270) and Um(2791)) located at the peptidyl transferase centre of 21S rRNA. We demonstrate here that the yeast nuclear genome encodes a mitochondrial protein, named Mrm2, which is required for methylating U(2791) of 21S rRNA, both in vivo and in vitro.