scholarly journals Role of C4 carbon fixation in Ulva prolifera, the macroalga responsible for the world’s largest green tides

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Dongyan Liu ◽  
Qian Ma ◽  
Ivan Valiela ◽  
Donald M. Anderson ◽  
John K. Keesing ◽  
...  

Abstract Most marine algae preferentially assimilate CO2 via the Calvin-Benson Cycle (C3) and catalyze HCO3− dehydration via carbonic anhydrase (CA) as a CO2-compensatory mechanism, but certain species utilize the Hatch-Slack Cycle (C4) to enhance photosynthesis. The occurrence and importance of the C4 pathway remains uncertain, however. Here, we demonstrate that carbon fixation in Ulva prolifera, a species responsible for massive green tides, involves a combination of C3 and C4 pathways, and a CA-supported HCO3− mechanism. Analysis of CA and key C3 and C4 enzymes, and subsequent analysis of δ13C photosynthetic products showed that the species assimilates CO2 predominately via the C3 pathway, uses HCO3− via the CA mechanism at low CO2 levels, and takes advantage of high irradiance using the C4 pathway. This active and multi-faceted carbon acquisition strategy is advantageous for the formation of massive blooms, as thick floating mats are subject to intense surface irradiance and CO2 limitation.

2019 ◽  
Vol 227 ◽  
pp. 106329 ◽  
Author(s):  
Changyou Wang ◽  
Rongguo Su ◽  
Laodong Guo ◽  
Bin Yang ◽  
Ying Zhang ◽  
...  

Endocrinology ◽  
2019 ◽  
Vol 161 (2) ◽  
Author(s):  
Sandra Handgraaf ◽  
Rodolphe Dusaulcy ◽  
Florian Visentin ◽  
Jacques Philippe ◽  
Yvan Gosmain

Abstract Characterization of enteroendocrine L cells in diabetes is critical for better understanding of the role of glucagon-like peptide-1 (GLP-1) in physiology and diabetes. We studied L-cell transcriptome changes including microRNA (miRNA) dysregulation in obesity and diabetes. We evaluated the regulation of miRNAs through microarray analyses on sorted enteroendocrine L cells from control and obese glucose-intolerant (I-HFD) and hyperglycemic (H-HFD) mice after 16 weeks of respectively low-fat diet (LFD) or high-fat diet (HFD) feeding. The identified altered miRNAs were studied in vitro using the mouse GLUTag cell line to investigate their regulation and potential biological functions. We identified that let-7e-5p, miR-126a-3p, and miR-125a-5p were differentially regulated in L cells of obese HFD mice compared with control LFD mice. While downregulation of let-7e-5p expression was observed in both I-HFD and H-HFD mice, levels of miR-126a-3p increased and of miR-125a-5p decreased significantly only in I-HFD mice compared with controls. Using miRNA inhibitors and mimics we observed that modulation of let-7e-5p expression affected specifically GLP-1 cellular content and basal release, whereas Gcg gene expression and acute GLP-1 secretion and cell proliferation were not affected. In addition, palmitate treatment resulted in a decrease of let-7e-5p expression along with an increase in GLP-1 content and release, suggesting that palmitate acts on GLP-1 through let-7e-5p. By contrast, modulation of miR-125a-5p and miR-126a-3p in the same conditions did not affect content or secretion of GLP-1. We conclude that decrease of let-7e-5p expression in response to palmitate may constitute a compensatory mechanism contributing to maintaining constant glycemia in obese mice.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hamish Patel ◽  
Reza Zamani

Abstract Long-term memories are thought to be stored in neurones and synapses that undergo physical changes, such as long-term potentiation (LTP), and these changes can be maintained for long periods of time. A candidate enzyme for the maintenance of LTP is protein kinase M zeta (PKMζ), a constitutively active protein kinase C isoform that is elevated during LTP and long-term memory maintenance. This paper reviews the evidence and controversies surrounding the role of PKMζ in the maintenance of long-term memory. PKMζ maintains synaptic potentiation by preventing AMPA receptor endocytosis and promoting stabilisation of dendritic spine growth. Inhibition of PKMζ, with zeta-inhibitory peptide (ZIP), can reverse LTP and impair established long-term memories. However, a deficit of memory retrieval cannot be ruled out. Furthermore, ZIP, and in high enough doses the control peptide scrambled ZIP, was recently shown to be neurotoxic, which may explain some of the effects of ZIP on memory impairment. PKMζ knockout mice show normal learning and memory. However, this is likely due to compensation by protein-kinase C iota/lambda (PKCι/λ), which is normally responsible for induction of LTP. It is not clear how, or if, this compensatory mechanism is activated under normal conditions. Future research should utilise inducible PKMζ knockdown in adult rodents to investigate whether PKMζ maintains memory in specific parts of the brain, or if it represents a global memory maintenance molecule. These insights may inform future therapeutic targets for disorders of memory loss.


Mäetagused ◽  
2021 ◽  
Vol 79 ◽  
pp. 35-54
Author(s):  
Tatsiana Valodzina ◽  
◽  
Tatsiana Marmysh ◽  

The article gives an overview of the folk culture mechanisms that helped to cope with the pandemic situation in Belorussia during the first wave of COVID-19 (until midsummer 2020). The article is based on the qualitative analysis of interview texts related to the pandemic as well as the content of internet users’ visual reactions (memes, poems, proverbs). In folk culture the mechanisms helping to overcome the crisis situation often have a ritual-magical nature. When describing the influence of the pandemic on some practices, the authors conclude that their performing in the crisis situation was especially important for the community. One of the ancient rituals activated for preventing the epidemic was the creation of a magic circle around the village by conducting a procession around the village with a ritual towel (‘rushnik-abydzionnik’), which had to be made within one day. On March 28, this one-day-ritual was performed in Minsk with the greatest possible adherence to tradition. The initiators and participants of the practice were mainly representatives of the Students Ethnographic Society. Not all women present knew how to spin or weave, but some of the simplest operations were mastered. The towel was carried around Minsk and brought to a stone on the site of a pagan temple in the centre of Minsk at the sunset. The towel was tied around the stone, and the latter was also covered with threads spun on the same day. The ritual relieved the tension of the participants and fostered awareness of their solidarity, strengthening collective networks, and the feeling of empathy and unity. COVID-19 also affected the living traditions in Belarus. Some traditional practices were cancelled or postponed. The spread of the pandemic created a negative backdrop for living traditions. However, a number of rites and ceremonies were carried out despite the pandemic in accordance with their spatial and temporal reference. Due to the difficult epidemiological situation, the usual order of ceremonies was changed – their duration was reduced without changing the traditional rite structure. Only local residents participated in the rituals; although, formerly, many journalists and tourists had come to the villages from different parts of the country on the days of the ceremonies. For tradition bearers, such practices during a pandemic are a way to relieve stress and to share problems with people with similar interests. Traditions are one of the constants of their life; maintaining them in times of crises stabilizes the community. The coronavirus pandemic has caused a powerful explosion of folk art. The texts of various genres, both oral and written (graphic), are rapidly spreading on the Internet. A large number of them are based on the traditional worldview of Belarusians and are expressed in traditional forms (alterations, ditties, anecdotes, anti-sayings, paroemias, etc.). The role of humour has grown tremendously. Jokes and laughter in the face of an external threat are a compensatory mechanism that helps to overcome fear and uncertainty, and common laughter unites and helps to learn new rules of behaviour. Humour is not concerned with the threat of getting ill, but rather individual hygiene practices, the situation of quarantine, and circumstances of the new reality. Thus, humorous folklore becomes a way to adapt to new norms and to overcome fear and instability.


2014 ◽  
Vol 460 (2) ◽  
pp. 223-235 ◽  
Author(s):  
Abdul Haseeb Shah ◽  
Ashutosh Singh ◽  
Sanjiveeni Dhamgaye ◽  
Neeraj Chauhan ◽  
Patrick Vandeputte ◽  
...  

QDR proteins of C. albicans do not carry out their conserved transport function, rather they affect the pathogenesis of the organism and their deletion mutants also show architectural defects in biofilms and massive remodelling of lipids as a compensatory mechanism to sustain their loss.


2019 ◽  
Vol 6 (4) ◽  
pp. 825-838 ◽  
Author(s):  
Yongyu Zhang ◽  
Peimin He ◽  
Hongmei Li ◽  
Gang Li ◽  
Jihua Liu ◽  
...  

Abstract The Ulva prolifera green tides in the Yellow Sea, China, which have been occurring since 2007, are a serious environmental problem attracting worldwide attention. Despite extensive research, the outbreak mechanisms have not been fully understood. Comprehensive analysis of anthropogenic and natural biotic and abiotic factors reveals that human activities, regional physicochemical conditions and algal physiological characteristics as well as ocean warming and biological interactions (with microorganism or other macroalgae) are closely related to the occurrence of green tides. Dynamics of these factors and their interactions could explain why green tides suddenly occurred in 2007 and decreased abruptly in 2017. Moreover, the consequence of green tides is serious. The decay of macroalgal biomass could result in hypoxia and acidification, possibly induce red tide and even have a long-lasting impact on coastal carbon cycles and the ecosystem. Accordingly, corresponding countermeasures have been proposed in our study for future reference in ecosystem management strategies and sustainable development policy.


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