LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae

Microalgae are unicellular photosynthetic organisms considered as potential alternative sources for biomass, biofuels or high value products. However, limited biomass productivity is commonly experienced in their cultivating system despite their high potential. One of the reasons for this limitation is the high thermal dissipation of the light absorbed by the outer layers of the cultures exposed to high light caused by the activation of a photoprotective mechanism called non-photochemical quenching (NPQ). In the model organism for green algae Chlamydomonas reinhardtii, NPQ is triggered by pigment binding proteins called light-harvesting-complexes-stress-related (LHCSRs), which are over-accumulated in high light. It was recently reported that biomass productivity can be increased both in microalgae and higher plants by properly tuning NPQ induction. In this work increased light use efficiency is reported by introducing in C. reinhardtii a LHCSR3 gene under the control of Heat Shock Protein 70/RUBISCO small chain 2 promoter in a npq4 lhcsr1 background, a mutant strain knockout for all LHCSR genes. This complementation strategy leads to a low expression of LHCSR3, causing a strong reduction of NPQ induction but is still capable of protecting from photodamage at high irradiance, resulting in an improved photosynthetic efficiency and higher biomass accumulation

Multisignal control of expression of the LHCX protein family in the marine diatom Phaeodactylum tricornutum

Diatoms are phytoplanktonic organisms that grow successfully in the ocean where light conditions are highly variable. Studies of the molecular mechanisms of light acclimation in the marine diatom Phaeodactylum tricornutum show that carotenoid de-epoxidation enzymes and LHCX1, a member of the light-harvesting protein family, both contribute to dissipate excess light energy through non-photochemical quenching (NPQ). In this study, we investigate the role of the other members of the LHCX family in diatom stress responses. Our analysis of available genomic data shows that the presence of multiple LHCX genes is a conserved feature of diatom species living in different ecological niches. Moreover, an analysis of the levels of four P. tricornutum LHCX transcripts in relation to protein expression and photosynthetic activity indicates that LHCXs are differentially regulated under different light intensities and nutrient starvation, mostly modulating NPQ capacity. We conclude that multiple abiotic stress signals converge to regulate the LHCX content of cells, providing a way to fine-tune light harvesting and photoprotection. Moreover, our data indicate that the expansion of the LHCX gene family reflects functional diversification of its members which could benefit cells responding to highly variable ocean environments

A systems-wide understanding of photosynthetic acclimation in algae and higher plants

The ability of phototrophs to colonise different environments relied on the robust protection against oxidative stress in phototrophs, a critical requirement for the successful evolutionary transition from water to land. Photosynthetic organisms have developed numerous strategies to adapt their photosynthetic apparatus to changing light conditions in order to optimise their photosynthetic yield, crucial for life to exist on Earth. Photosynthetic acclimation is an excellent example of the complexity of biological systems, in which highly diverse processes, ranging from electron excitation over protein protonation to enzymatic processes coupling ion gradients with biosynthetic activity interact on drastically different timescales, ranging from picoseconds to hours. An efficient functioning of the photosynthetic apparatus and its protection is paramount for efficient downstream processes including metabolism and growth. Modern experimental techniques can be successfully integrated with theoretical and mathematical models to promote our understanding of underlying mechanisms and principles. This Review aims to provide a retrospective analysis of multidisciplinary photosynthetic acclimation research carried out by members of the Marie Curie Initial Training Project “AccliPhot”, placing the results in a wider context. The Review also highlights the applicability of photosynthetic organisms for industry, particularly with regards to the cultivation of microalgae. It aims to demonstrate how theoretical concepts can successfully complement experimental studies broadening our knowledge of common principles in acclimation processes in photosynthetic organisms, as well as in the field of applied microalgal biotechnology

Light Stress and Photoprotection in Green algae, Mosses and Diatoms

The molecular bases of responses to light excess in photosynthetic organismshaving different evolutionary histories and belonging to different lineages are still not completely characterized.Therefore I explored the functions of photoprotective antennae in green algae, mosses and diatoms, together withthe role of the two xanthophyll cycles present in diatoms.I studied the Light Harvesting Complex Stress-Related (LHCSR) proteins in different organisms. In thegreen alga Chlamydomonas reinhardtii, LHCSR3 is a protein important for photoprotection. I used site-specificmutagenesis in vivo and in vitro and identified three residues of LHCSR3 that are responsible for its activation.With the moss Physcomitrella patens I studied the in vitro spectroscopic and quenching characteristics ofdifferent pigment-binding mutants of the protein LHCSR1, focusing in particular on chlorophylls A2 and A5.LHCSRs in diatoms are named LHCXs, and in Phaeodactylum tricornutum I found that multiple abioticstress signals converge to regulate the LHCX content of cells, providing a way to fine-tune light harvesting andphotoprotection.The other main driver of photoprotection in diatoms is the xanthophyll cycle. Here I found that the accu-mulation of viola- and zeaxanthin in P. tricornutum have a negative effect in the development of NPQ, showingthat zeaxanthin does not participate in the enhancing of NPQ in diatoms.Thanks to these studies done on different organisms, we gained a deeper knowledge on the shared character-istics and on the peculiar features about photoprotection in green algae, mosses and diatoms

Stress lumineux et photoprotection chez les algues vertes, mousses et diatomées

The molecular bases of responses to light excess in photosynthetic organisms having different evolutionary histories and belonging to different lineages are still not completely characterized. Therefore I explored the functions of photoprotective antennae in green algae, mosses and diatoms, together with the role of the two xanthophyll cycles present in diatoms.I studied the Light Harvesting Complex Stress-Related (LHCSR) proteins in different organisms. In the green alga Chlamydomonas reinhardtii, LHCSR3 is a protein important for photoprotection. I used site-specific mutagenesis in vivo and in vitro and identified three residues of LHCSR3 that are responsible for its activation.With the moss Physcomitrella patens I studied the in vitro spectroscopic and quenching characteristics of different pigment-binding mutants of the protein LHCSR1, focusing in particular on chlorophylls A2 and A5.LHCSRs in diatoms are named LHCXs, and in Phaeodactylum tricornutum I found that multiple abiotic stress signals converge to regulate the LHCX content of cells, providing a way to fine-tune light harvesting and photoprotection.The other main driver of photoprotection in diatoms is the xanthophyll cycle. Here I found that the accumulation of viola- and zeaxanthin in P. tricornutum have a negative effect in the development of NPQ, showing that zeaxanthin does not participate in the enhancing of NPQ in diatoms.Thanks to these studies done on different organisms, we gained a deeper knowledge on the shared characteristics and on the peculiar features about photoprotection in green algae, mosses and diatoms.Les bases moléculaires des réponses aux excès de lumière chez les organismes photosynthétiques appartenant à des lignées évolutives distinctes ne sont toujours pas complètement caractérisées. Par conséquent, j'ai caractérisé des antennes photoprotectrices dans les algues vertes, les mousses et les diatomées et j'ai exploré la fonction de deux cycles de xanthophylles chez les diatomées.J'ai étudié les protéines Light Harvesting Complex Stress-Related (LHCSR) dans tous ces organismes. Chez l'algue verte Chlamydomonas reinhardtii, j’ai identifié par mutagénèse dirigée, complémentation fonctionnelle et par une approche biochimique les acides aminés responsables de l'activation de LHCSR3, une protéine importante pour le NPQ.Dans le modèle de mousse Physcomitrella patens, j'ai etudié in vitro les caractéristiques spectroscopique ainsi que le quenching de différents mutants de liaison de pigment sur la protéine LHCSR1.Les protéines LHCSR dans les diatomées sont nommées LHCXs, et dans Phaeodactylum tricornutum j'ai montré que l'expansion de la famille des gènes LHCX reflète une diversification fonctionnelle de ces protéines permettant de répondre à des environnements marins très variables.L'autre acteur principal de la photoprotection dans les diatomées est le cycle des xanthophylles. J’ai trouvé que l'accumulation d'une grande quantité de viola- et zéaxanthin a un effet négatif sur le NPQ montrant que la zéaxanthin ne participe pas au NPQ chez diatomées.Grâce à ces études effectuées, nous avons acquis une connaissance plus approfondie sur les caractéristiques communes et les spécificités de la photoprotection.chez différents organismes

Engineering the Unicellular Alga Phaeodactylum tricornutum for Enhancing Carotenoid Production

Microalgae represent a promising resource for the production of beneficial natural compounds due to their richness in secondary metabolites and easy cultivation. Carotenoids feature among distinctive compounds of many microalgae, including diatoms, which owe their golden color to the xanthophyll fucoxanthin. Carotenoids have antioxidant, anti-obesity and anti-inflammatory properties, and there is a considerable market demand for these compounds. Here, with the aim to increase the carotenoid content in the model diatom Phaeodactylum tricornutum, we exploited genetic transformation to overexpress genes involved in the carotenoid biosynthetic pathway. We produced transgenic lines over-expressing simultaneously one, two or three carotenoid biosynthetic genes, and evaluated changes in pigment content with high-performance liquid chromatography. Two triple transformants over-expressing the genes Violaxanthin de-epoxidase (Vde), Vde-related (Vdr) and Zeaxanthin epoxidase 3 (Zep3) showed an accumulation of carotenoids, with an increase in the fucoxanthin content up to four fold. Vde, Vdr and Zep3 mRNA and protein levels in the triple transformants were coherently increased. The exact role of these enzymes in the diatom carotenoid biosynthetic pathway is not completely elucidated nevertheless our strategy successfully modulated the carotenoid metabolism leading to an accumulation of valuable compounds, leading the way toward improved utilization of microalgae in the field of antioxidants

Dynamic Changes between Two LHCX-Related Energy Quenching Sites Control Diatom Photoacclimation

International audienceMarine diatoms are prominent phytoplankton organisms that perform photosynthesis in extremely variable environments. Diatoms possess a strong ability to dissipate excess absorbed energy as heat via nonphotochemical quenching (NPQ). This process relies on changes in carotenoid pigment composition (xanthophyll cycle) and on specific members of the light-harvesting complex family specialized in photoprotection (LHCXs), which potentially act as NPQ effectors. However, the link between light stress, NPQ, and the existence of different LHCX isoforms is not understood in these organisms. Using picosecond fluorescence analysis, we observed two types of NPQ in the pennate diatom Phaeodactylum tricornutum that were dependent on light conditions. Short exposure of low-light-acclimated cells to high light triggers the onset of energy quenching close to the core of photosystem II, while prolonged light stress activates NPQ in the antenna. Biochemical analysis indicated a link between the changes in the NPQ site/mechanism and the induction of different LHCX isoforms, which accumulate either in the antenna complexes or in the core complex. By comparing the responses of wild-type cells and transgenic lines with a reduced expression of the major LHCX isoform, LHCX1, we conclude that core complex-associated NPQ is more effective in photoprotection than is the antenna complex. Overall, our data clarify the complex molecular scenario of light responses in diatoms and provide a rationale for the existence of a degenerate family of LHCX proteins in these algae

The European Society of Thoracic Surgeons (ESTS) lung neuroendocrine tumors (NETs) database

Histological characteristics and clinical behaviour define lung neuroendocrine tumors (NETs), which are classified into four groups: typical (TC) and atypical carcinoids (AC), large-cell neuroendocrine carcinomas (LCNCs) and small-cell lung cancers (SCLCs). Historically, outcome and treatment of these rare neoplasms have been based on small, usually mono-institutional clinical series. Furthermore, their rarity makes quite impossible to design randomised clinical trial to compare different treatments especially in unusual clinical presentations. In 2012, the European Society of Thoracic Surgeons (ESTS) launched a new working-group, specifically dedicated to lung NETs, with the aim to develop modern knowledge on biology and behaviour of these tumors, and to disseminate it within the scientific community. A dedicated retrospective database was at first developed and sent to all the ESTS centres interested to this project. More than 2,000 operated NETs cases have been rapidly collected, and they represented the clinical substrate of several published scientific studies. The retrospective data collection intrinsic limitations in term of patients' selection and treatment, along with the problem of possible missing data, were the reasons why the ESTS NETs working-group decided in 2015 to design and promote a new prospective database, employing the official ESTS platform. The aim of this review paper is to report the ESTS Lung NETs working-group history and to explain the architecture and use of the lung NETs databases

The European Society of Thoracic Surgeons (ESTS) lung neuroendocrine tumors (NETs) database

Histological characteristics and clinical behaviour define lung neuroendocrine tumors (NETs), which are classified into four groups: typical (TC) and atypical carcinoids (AC), large-cell neuroendocrine carcinomas (LCNCs) and small-cell lung cancers (SCLCs). Historically, outcome and treatment of these rare neoplasms have been based on small, usually mono-institutional clinical series. Furthermore, their rarity makes quite impossible to design randomised clinical trial to compare different treatments especially in unusual clinical presentations. In 2012, the European Society of Thoracic Surgeons (ESTS) launched a new working-group, specifically dedicated to lung NETs, with the aim to develop modern knowledge on biology and behaviour of these tumors, and to disseminate it within the scientific community. A dedicated retrospective database was at first developed and sent to all the ESTS centres interested to this project. More than 2,000 operated NETs cases have been rapidly collected, and they represented the clinical substrate of several published scientific studies. The retrospective data collection intrinsic limitations in term of patients' selection and treatment, along with the problem of possible missing data, were the reasons why the ESTS NETs working-group decided in 2015 to design and promote a new prospective database, employing the official ESTS platform. The aim of this review paper is to report the ESTS Lung NETs working-group history and to explain the architecture and use of the lung NETs databases

Asthma in patients admitted to emergency department for COVID-19: prevalence and risk of hospitalization

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