Daily Regulation of Key Metabolic Pathways in Two Seagrasses Under Natural Light Conditions

The circadian clock is an endogenous time-keeping mechanism that enables organisms to adapt to external environmental cycles. It produces rhythms of plant metabolism and physiology, and interacts with signaling pathways controlling daily and seasonal environmental responses through gene expression regulation. Downstream metabolic outputs, such as photosynthesis and sugar metabolism, besides being affected by the clock, can also contribute to the circadian timing itself. In marine plants, studies of circadian rhythms are still way behind in respect to terrestrial species, which strongly limits the understanding of how they coordinate their physiology and energetic metabolism with environmental signals at sea. Here, we provided a first description of daily timing of key core clock components and clock output pathways in two seagrass species, Cymodocea nodosa and Zostera marina (order Alismatales), co-occurring at the same geographic location, thus exposed to identical natural variations in photoperiod. Large differences were observed between species in the daily timing of accumulation of transcripts related to key metabolic pathways, such as photosynthesis and sucrose synthesis/transport, highlighting the importance of intrinsic biological, and likely ecological attributes of the species in determining the periodicity of functions. The two species exhibited a differential sensitivity to light-to-dark and dark-to-light transition times and could adopt different growth timing based on a differential strategy of resource allocation and mobilization throughout the day, possibly coordinated by the circadian clock. This behavior could potentially derive from divergent evolutionary adaptations of the species to their bio-geographical range of distributions

Depth-specific fluctuations of gene expression and protein abundance modulate the photophysiology in the seagrass <i>Posidonia oceanica</i>

Here we present the results of a multiple organizational level analysis conceived to identify acclimative/adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily fluctuations in the light environment, at contrasting depths. We assessed changes in photophysiological parameters, leaf respiration, pigments, and protein and mRNA expression levels. The results show that the diel oscillations of P. oceanica photophysiological and respiratory responses were related to transcripts and proteins expression of the genes involved in those processes and that there was a response asynchrony between shallow and deep plants probably caused by the strong differences in the light environment. The photochemical pathway of energy use was more effective in shallow plants due to higher light availability, but these plants needed more investment in photoprotection and photorepair, requiring higher translation and protein synthesis than deep plants. The genetic differentiation between deep and shallow stands suggests the existence of locally adapted genotypes to contrasting light environments. The depth-specific diel rhythms of photosynthetic and respiratory processes, from molecular to physiological levels, must be considered in the management and conservation of these key coastal ecosystems

One year of Lamivudine therapy for portuguese patients with chronic hepatitis B.

OBJECTIVE: To further verify the efficacy and safety of locally manufactured lamivudine on patients with chronic hepatitis B (CHB). METHODS: 2200 patients with CHB were recruited and received lamivudine orally 100 mg once daily for 12 months. The efficacy assessments included virologic response rate (defined by the absence of serum HBV DNA, HBeAg loss and HBeAg/HBeAb seroconversion), percentage of patients with normalization of alanine aminotransferase (ALT). Meanwhile improvement of quality of life (QOL) measured by mos SF-36 QOL questionnaire and liver histology evaluation were conducted in some patients. The safety assessments included adverse events, serious adverse events and laboratory abnormalities. All 2200 patients received at least one dose of medication and were all included in the safety population. RESULTS: Ninety seven percent of patients (2137/2200) recruited were HBV DNA positive by dot blot (sensitivity GRT or equal to 1.0 pg/ml) at baseline. At the end of 12 months treatment, HBV DNA was undetectable in 80% patients (1538/1920) with HBV DNA positive before treatment. Among the 79%(1744/2200) of the patients recruited had positive HBV DNA accompanied abnormal ALT levels at baseline, 72% patients became ALT normal. And among the 84% (1843/2200) of the patients recruited were HBV DNA and HBeAg positive, anti-HBe negative, 16% (269/1650) patients achieved HBeAg/HBeAb seroconversion after 12 months of lamivudine treatment. The HBeAg/HBeAb seroconversion rate was positive correlation to the ALT level before treatment. A total of 304 patients completed the health-related QOL questionnaire. After 12 months treatment, lamivudine improved both their physical and mental health, especially for their mental health. 133 evaluable, paired liver biopsies were obtained for histological assessment, among whom 115 patients had abnormal ALT levels at baseline. Compared with pre-treatment most of their liver injury got alleviated (51.9%) or no further deterioration (36%), only 12% worsening. During the 12 months treatment, 9% patients withdrew from the study and 17% patients showed at least one adverse event, mild or moderate. There were no obvious difference between this study and the previously reported lamivudine Phase II or III study with regard to the kinds, incidence and severity of adverse events. CONCLUSION: The efficacy and safety profile of the locally manufactured lamivudine 100 mg tablets are similar with those of the previously reported available lamivudine tablets imported in treating Chinese chronic hepatitis B patients

Genomewide transcriptional reprogramming in the seagrass Cymodocea nodosa under experimental ocean acidification

Here, we report the first use of massive-scale RNA-sequencing to explore seagrass response to CO2-driven ocean acidification (OA). Large-scale gene expression changes in the seagrass Cymodocea nodosa occurred at CO2 levels projected by the end of the century. C.&nbsp;nodosa transcriptome was obtained using Illumina RNA-Seq technology and de novo assembly, and differential gene expression was explored in plants exposed to short-term high CO2/low pH conditions. At high pCO2, there was a significant increased expression of transcripts associated with photosynthesis, including light reaction functions and CO2 fixation, and also to respiratory pathways, specifically for enzymes involved in glycolysis, in the tricarboxylic acid cycle and in the energy metabolism of the mitochondrial electron transport. The upregulation of respiratory metabolism is probably supported by the increased availability of photosynthates and increased energy demand for biosynthesis and stress-related processes under elevated CO2 and low pH. The upregulation of several chaperones resembling heat stress-induced changes in gene expression highlighted the positive role these proteins play in tolerance to intracellular acid stress in seagrasses. OA further modifies C.&nbsp;nodosa secondary metabolism inducing the transcription of enzymes related to biosynthesis of carbon-based secondary compounds, in particular the synthesis of polyphenols and isoprenoid compounds that have a variety of biological functions including plant defence. By demonstrating which physiological processes are most sensitive to OA, this research provides a major advance in the understanding of seagrass metabolism in the context of altered seawater chemistry from global climate change

Effectiveness and consistency of a suite of descriptors to assess the ecological status of seagrass meadows (Posidonia oceanica L. Delile)

The increasing rate of human-induced environmental changes on coastal marine ecosystems has created a demand for effective descriptors, in particular for those suitable for monitoring the status of seagrass meadows. Growing evidence has supported the useful application of biochemical and genetic descriptors such as secondary metabolite synthesis, photosynthetic activity and genetic diversity. In the present study, we have investigated the effectiveness of different descriptors (traditional, biochemical and genetic) in monitoring seagrass meadow conservation status. The Posidonia oceanica meadow of Monterosso al Mare (Ligurian sea, NW Mediterranean) was subjected to the measurement of bed density, leaf biometry, total phenols, soluble protein and photosynthetic pigment content as well as to RAPD marker analysis. This suite of descriptors provided evidence of their effectiveness and convenient application as markers of the conservation status of P. oceanica and/or other seagrasses. Biochemical/genetic descriptors and those obtained by traditional methods depicted a well conserved meadow with seasonal variability and, particularly in summer, indicated a healthier condition in a portion of the bed (station C), which was in agreement with the physical and sedimentological features of the station. Our results support the usefulness of introducing biochemical and genetic approaches to seagrass monitoring programs since they are effective indicators of plant physiological stress and environmental disturbance

M6A RNA methylation in marine plants: First insights and relevance for biological rhythms

Circadian regulations are essential for enabling organisms to synchronize physiology with environmental light-dark cycles. Post-transcriptional RNA modifications still represent an understudied level of gene expression regulation in plants, although they could play crucial roles in environmental adaptation. N6-methyl-adenosine (m6A) is the most prevalent mRNA modification, established by “writer” and “eraser” proteins. It influences the clockwork in several taxa, but only few studies have been conducted in plants and none in marine plants. Here, we provided a first inventory of m6A-related genes in seagrasses and investigated daily changes in the global RNA methylation and transcript levels of writers and erasers in Cymodocea nodosa and Zostera marina. Both species showed methylation peaks during the dark period under the same photoperiod, despite exhibiting asynchronous changes in the m6A profile and related gene expression during a 24-h cycle. At contrasting latitudes, Z. marina populations displayed overlapping daily patterns of the m6A level and related gene expression. The observed rhythms are characteristic for each species and similar in populations of the same species with different photoperiods, suggesting the existence of an endogenous circadian control. Globally, our results indicate that m6A RNA methylation could widely contribute to circadian regulation in seagrasses, potentially affecting the photo-biological behaviour of these plants