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Influence of the quantity and quality of light on photosynthetic periodicity in coral endosymbiotic algae.

ABSTRACT: Symbiotic corals, which are benthic organisms intimately linked with their environment, have evolved many ways to deal with fluctuations in the local marine environment. One possible coping mechanism is the endogenous circadian clock, which is characterized as free running, maintaining a ~24 h periodicity of circuits under constant stimuli or in the absence of external cues. The quantity and quality of light were found to be the most influential factors governing the endogenous clock for plants and algae. Unicellular dinoflagellate algae are among the best examples of organisms that exhibit circadian clocks using light as the dominant signal. This study is the first to examine the effects of light intensity and quality on the rhythmicity of photosynthesis in the symbiotic dinoflagellate Symbiodinium sp., both as a free-living organism and in symbiosis with the coral Stylophora pistillata. Oxygen production measurements in Symbiodinium cultures exhibited rhythmicity with a periodicity of approximately 24 h under constant high light (LL), whereas under medium and low light, the cycle time increased. Exposing Symbiodinium cultures and corals to spectral light revealed different effects of blue and red light on the photosynthetic rhythm, specifically shortening or increasing the cycle time respectively. These findings suggest that the photosynthetic rhythm is entrained by different light cues, which are wired to an endogenous circadian clock. Furthermore, we provide evidence that mRNA expression was higher under blue light for two potential cryptochrome genes and higher under red light for a phytochrome gene isolated from Symbiodinium. These results offer the first evidence of the impact of the intensity and quality of light on the photosynthetic rhythm in algal cells living freely or as part of a symbiotic association. Our results indicate the presence of a circadian oscillator in Symbiodinium governing the photosynthetic apparatus through a light-induced signaling pathway that has yet to be described.

SUBMITTER: Sorek M

PROVIDER: S-EPMC3422335 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Influence of the quantity and quality of light on photosynthetic periodicity in coral endosymbiotic algae.

Sorek Michal M Levy Oren O

PloS one 20120817 8

Symbiotic corals, which are benthic organisms intimately linked with their environment, have evolved many ways to deal with fluctuations in the local marine environment. One possible coping mechanism is the endogenous circadian clock, which is characterized as free running, maintaining a ~24 h periodicity of circuits under constant stimuli or in the absence of external cues. The quantity and quality of light were found to be the most influential factors governing the endogenous clock for plants ...[more]

PMID: 22912840

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Project description:Benthic algae are associated with coral death in the form of stress and disease. It's been proposed that they release exudates, which facilitate invasion of potentially pathogenic microbes at the coral-algal interface, resulting in coral disease. However, the original source of these pathogens remains unknown. This study examined the ability of benthic algae to act as reservoirs of coral pathogens by characterizing surface associated microbes associated with major Caribbean and Indo-Pacific algal species/types and by comparing them to potential pathogens of two dominant coral diseases: White Syndrome (WS) in the Indo-Pacific and Yellow Band Disease (YBD) in the Caribbean. Coral and algal sampling was conducted simultaneously at the same sites to avoid spatial effects. Potential pathogens were defined as those absent or rare in healthy corals, increasing in abundance in healthy tissues adjacent to a disease lesion, and dominant in disease lesions. Potentially pathogenic bacteria were detected in both WS and YBD and were also present within the majority of algal species/types (54 and 100% for WS and YBD respectively). Pathogenic ciliates were associated only with WS and not YBD lesions and these were also present in 36% of the Indo-Pacific algal species. Although potential pathogens were associated with many algal species, their presence was inconsistent among replicate algal samples and detection rates were relatively low, suggestive of low density and occurrence. At the community level, coral-associated microbes irrespective of the health of their host differed from algal-associated microbes, supporting that algae and corals have distinctive microbial communities associated with their tissue. We conclude that benthic algae are common reservoirs for a variety of different potential coral pathogens. However, algal-associated microbes alone are unlikely to cause coral death. Initial damage or stress to the coral via other competitive mechanisms is most likely a prerequisite to potential transmission of these pathogens.

Project description:Purpose: Dietary fat-driven hyperphagia increase intestinal growth and permeability and create microbial imbalance in the gut. Over-nutrition coupled with increase in intestinal nutrient absorbance capacity then lead to nutrient overload in the liver, visceral adipose tissue followed by ectopic fat deposition with consequential lipotoxicity and inflammation. We investigated how protein quantity (10-30%) and quality (casein and whey) interact with dietary fat (20-55%) to affect these outcomes in adult mice. High (30%) protein groups showed differential response to high fat diets (40 and 55% fat) and these groups were selected for RNA-seq experiments. RNA-seq was performed on RNA extracted from the jejunum, liver and hypothalami of mice exposed to the different diets. Methods: C57BL/6J male mice used in this work. All mice were fed a 20% kcal casein, 10% kcal fat and 70% kcal carbohydrate diet (Research Diets; USA; D12450Bi), until they were aged 20 weeks. Following 15 weeks of intake of the latter diet (at age 20 weeks), all animals were weight matched and randomly allocated to different groups and switched to experimental diets for 12 weeks. After 12 weeks of dietary interventions all animals were sacrificed and dissected. Methods: The dietary treatments consisted of 3 different levels of dietary fat (20, 40 and 55%) combined with 3 different levels of protein (10, 20 and 30%), each replicated with the protein coming from either casein (CAS) (diet codes: D17052701- D17052709) or whey protein isolate (WPI) (diet codes: D17052710- D17052718). The levels of cellulose and sucrose were fixed at 5% by weight and energy respectively. The carbohydrate (starch) amount was reduced in parallel with increase of dietary protein and fat. All these diets can be ordered direct from research diets (www.researchdiets.com) using the diet codes provided. The 18 different treatments with 12 mice per group, where mice were housed in cages of 3 animals. Methods: The hypothalamus, liver, and jejunum of all animals from 30% protein groups (6 diets [D17052703, D17052706, D17052709, D17052712, D17052715, D17052718], 71 animals) were collected. Total RNA was extracted from hypothalamic blocks using Tri-reagent (Sigma) and from liver and jejunum using the RNeasy Mini Kit (QIAGEN, 74104) according to manufacture instructions. Hypothalamic RNA was paired-end (PE) sequenced by PE100 on BGISEQ-500 platform at Beijing Genomic Institute (PE 2 x 75 bp, 150 bp per fragment, 20M read-pairs per sample). Sequencing of liver and jejunal RNA was performed using the NovaSeq 6000 platform (chemistry V4.0 Illumina) at Macrogen Inc Seoul, South Korea (PE 2 x 75 bp, 150 bp per fragment, 25M read-pairs per sample). Raw sequence reads were obtained in FASTQ format and these sequence reads were quality assessed using the software FastQC (v 0.111.58; http://www.bioinformatics.babraham.ac.uk/projects/fastqc/). Sequences from all samples were quality trimmed, and cleaned of adaptor sequences using BBDuk java package to trim Illumina adapter sequences. On average 0.1% of the bases were trimmed per sample. Trimmed reads were aligned to the Mus musculus reference genome assembly GRCm38 (ftp://ftp.ensembl.org/pub/release-96/fasta/mus_musculus/dna/) using STAR RNA-seq aligner v2.5.2, and uniquely mapped read counts per Ensembl annotated gene/ transcript were estimated using the STAR -- quantMode option. Genes with zero read counts across all samples as well as non-protein coding genes were removed prior to subsequent analysis. Differential gene expression analysis and data transformations and visualization were carried out using DeSeq2 v1.18.1 in R 3.5.2. Sample clustering was carried out on variance stabilizing transformed data and visualised using PCA. Differentially expressed genes lists were generated using a negative binomial generalized linear model and pairwise comparisons using each combination of fat and protein content in each tissue. P values were adjusted for multiple comparisons using a Benjamini and Hochberg (B-H) method. DE genes with an adjusted P value < 0.05 were used for further DE gene data exploration and pathway analysis. The fold changes and p values were loaded into the Ingenuity Pathway Analysis (IPA) program (Ingenuity Systems; http://www.ingenuity.com/) for core analysis. IPA Knowledge Database was used to analyse the dietary impacts on canonical pathways and upstream regulators available in IPA. Results: Differential gene expression and IPA results revealed that jejunal immunity of the high (30%) CAS fed groups at 40 and 55% fat was oriented toward pro-inflammatory responses, whereas the corresponding WPI fed groups showed a reduction of inflammation. The liver transcriptome reveals genes involved in FA/lipid uptake and synthesis to be upregulated and genes involved in FA/lipid degradation were downregulated following a proportional increase of dietary fat (20 to 55%) in 30% CAS fed animals and these effects were not seen in WPI fed animals. In the hypothalamus, the intake of 40 and 55% fat significantly increased the number of differentially expressed genes compared to 20% fat. The effect of protein quality on hypothalamic gene expression (CAS vs WPI) was only seen at the highest fat content (55%), where several changes in signalling pathways were seen in WPI relative to CAS. These include a decreased reactive oxygen species production, reduction interleukin and chemokine inflammatory pathways and increased oxidative phosphorylation compared with mice fed CAS and 55% fat. Conclusions: Analysis of jejunal, liver and hypothalamic transcriptomic revealed that the intake of high WPI impeded the negative effects of high fat feeding (increased lipogenesis in the liver, inflammation, activation of disease-related pathways etc.), whereas the intake of high CAS exacerbated these effects. The data highlight the importance of selecting proteins rich in essential amino acids, for improving the metabolic outcomes of high fat diet.

Dataset Information

Influence of the quantity and quality of light on photosynthetic periodicity in coral endosymbiotic algae.

Publications

Influence of the quantity and quality of light on photosynthetic periodicity in coral endosymbiotic algae.

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