Project description:Mangrove plants are the demonstrated woody plants in tropical and subtropical coastal area with great ecological and economic importance. However, due to the extreme global climate change and increased human activities, mangroves is suffering a dramatic declining worldwide. Lumnitzera littorea (Jack) Voigt is one of the most endangered mangrove species in China. A comprehensive understanding on its resistance mechanisms to low ambient temperature help us to better conserve and restore L. littorea. In the current study, we performed comparative transcriptome analysis to investigate the genome-wide changes of gene expression profile in L. littorea under chilling stress (8°C day/5°C night) over normal condition (25°C day/23°C night). The low temperature suppressed fatty acid elongation and protein phosphorylation in L. littorea, while induced calcium ion binding process and signaling transduction, suggesting an activation of cold-stress sensing and signaling in L. littorea. Combining our analysis with our previous physiological assays, we showed a substantial photoinhibition occurring in the seedlings of L. littorea with the decrease of ambient temperature, and the synthesis of photosystem II reaction center protein D1 and peroxidase-involved scavenging of reactive oxygen species (ROS) were enhanced accordingly to combat the adverse impacts. Finally, we highlighted the biological significance of post-transcriptional regulation, including RNA binding and surveillance, in coping with cold stress in L. littorea. Collectively, our findings provide a global view to the resistance mechanisms of chilling stress in L. littorea, and valuable genetic resources to assist the protection and restoration of L. littorea.
Project description:Background: Array comparative genomic hybridization (aCGH) is commonly used to screen different types of genetic variation in humans and model species. Here, we performed aCGH using an oligonucleotide gene-expression array for a non-model species, the intertidal snail Littorina saxatilis. First, we tested what types of genetic variation can be detected by this method using direct re-sequencing and comparison to the Littorina genome draft. Secondly, we performed a genome-wide comparison of four closely related Littorina species: L. fabalis, L. compressa, L. arcana and L. saxatilis and of populations of L. saxatilis found in Spain, Britain and Sweden. Finally, we tested whether we could identify genetic variation underlying M-bM-^@M-^\CrabM-bM-^@M-^] and M-bM-^@M-^\WaveM-bM-^@M-^] ecotypes of L. saxatilis. Results: We could reliably detect copy number variations, deletions and high sequence divergence (i.e. above 3%), but not single nucleotide polymorphisms. The overall hybridization pattern and number of significantly diverged genes were in close agreement with earlier phylogenetic reconstructions based on single genes. The trichotomy of L. arcana, L. compressa and L. saxatilis could not be resolved and we argue that these divergence events have occurred recently and very close in time. We found evidence for high levels of segmental duplication in the Littorina genome (10% of the transcripts represented on the array and up to 23% of the analyzed genomic fragments); duplicated genes and regions were mostly the same in all analyzed species. Finally, this method discriminated geographically distant populations of L. saxatilis, but we did not detect any significant genome divergence associated with ecotypes of L. saxatilis. Conclusions: The present study provides new information on the sensitivity and the potential use of oligonucleotide arrays for genotyping of non-model organisms. Applying this method to Littorina species yields insights into genome evolution following the recent species radiation and supports earlier single-gene based phylogenies. Genetic differentiation of L. saxatilis ecotypes was not detected in this study, despite pronounced innate phenotypic differences. The reason may be that these differences are due to single-nucleotide polymorphisms. Genomic DNA samples of L. fabalis, L. compressa, L. arcana and 3 geographic populations x 2 ecotypes of L. saxatilis (n=4 per group) have been hybridized to a transcriptomic oligoarray.