No summary available.

Ribosomal RNA in fungi is encoded by a series of genes and spacers included in a large operon present in 100 tandem repeats, normally in a single locus. The multigene nature of this locus was somehow masked by Sanger sequencing, which produces a single sequence reporting the prevalent nucleotide of each site. The introduction of next generation sequencing led to deeper knowledge of the individual sequences (reads) and therefore of the variants between the same DNA sequences located in different tandem repeats. In this framework, NGS sequencing of the rDNA region was used to elucidate the extent of intra- and inter-genomic variation at both the strain and species level. Specifically, the use of an innovative NGS technique allowed the high-throughput high-depth sequencing of the ITS1-LSU D1/D2 amplicons of 252 strains belonging to four opportunistic yeast species of the genus Candida. Results showed the presence of a large extent of variability among strains and species. These variants were differently distributed throughout the analyzed regions with a higher concentration within the Internally Transcribed Spacer (ITS) region, suggesting that concerted evolution was not able to totally homogenize these sequences. Both the internal variability and the SNPs between strain can be used for a deep typing of the strains and to study their ecology.

The transfer of Nicotiana tabacum plants grown in low light (60 micromoles quanta per square meter per second) to higher light (360 micromoles quanta per square meter per second) was previously shown to induce adaptive stimulation of photosynthetic capacities. The variations of ribulose bisphosphate carboxylase/oxygenase (RubisCo) expression in mature leaves was examined as a result of this acclimation. Maximum or initial activities increased markedly after low- to high-light transfer with a maximum effect after 2 to 3 days. The higher activity is mainly explained by RubisCo protein synthesis as shown by immuno-rocket technique. Small subunits of RubisCo (SSU) mRNA relative content determined by hybridization of total RNA with DNA probe by Dot-blot method, followed the same pattern as RubisCo quantity. The magnitude of this response was amplified when more contrasting light conditions (25 versus 360 micromoles per square meter per second) were established on the same leaf: RubisCo activity, RubisCo protein, and SSU mRNA contents decreased in the shaded zone and increased in the high-light zone within 1 day. After 2 days the shade/light ratio was 1 to 3 for RubisCo protein and 1 to 4 for SSU-RNA, whereas the ratios remained equal to one in controls. Hybridization of the same RNA extracts with large subunits of RubisCo (LSU) probe showed no variation in LSU-RNA content. So in green adult leaves, the expression of SSU and LSU genes is regulated differently. The observed white light quantitative effect on RubisCo expression was not dependent on the photosynthetic rate or assimilate content since low CO 2 concentration around the leaf after the light shift did not modify the response.

Ciguatera poisoning (CP) is a foodborne disease caused by eating seafood containing ciguatoxins from benthic dinoflagellates of the genus Gambierdiscus. Moreover, the related Fukuyoa, which often coexists with Gambierdiscus, also produces potent marine toxins. Though CP is endemic to tropical regions, it is increasingly being reported elsewhere, including the Canary Islands (NE Atlantic). In the Balearic Islands (W Mediterranean), potentially ciguatoxin-producing species have been found frequently in recent years, but so far without documented CP. Since toxin production varies greatly among Gambierdiscus and Fukuyoa species, it is very important to be able to discriminate them and detect problematic species even when present in low densities. In this study we explored the potential of DNA metabarcoding targeting the D1-D2 LSU rDNA region to detect Gambierdiscus and Fukuyoa species alongside other dinoflagellates and microeukaryotes in the first such surveys of the studied archipelagos. The predominant species by far in the Balearics was G. australes, but in Gran Canaria, though abundant, it was often outnumbered by two more toxic species, G. excentricus and G. silvae. DNA metabarcoding recorded F. ruetzleri for the first time in the Canaries and G. carolinianus in the Balearics, both in very low relative abundance. A potential new species of Gambierdiscus (“occultus”) was detected in three Balearic Islands and Gran Canaria. Extensive intragenomic variation in the D1-D2 marker was found. We could also characterize the broader dinoflagellate community, including other harmful species and also parasitoids that may affect the dynamics of the dinoflagellates present. This research shows the power of LSU rDNA-based metabarcoding for studying benthic microeukaryotic communities.

No summary available.

No summary available.