Light Stress Research Articles

Enhancing carotenoid accumulation in Dunaliella bardawil by combined treatments with fulvic acid and optimized culture conditions

Natural carotenoids from microalgae have received more attention as an alternative source. In this study, fulvic acid (FA), a plant growth regulator, was used to enhance carotenoid accumulation in microalgae Dunaliella bardawil rich in lutein. However, the addition of FA promoted pigment synthesis but also exhibited an inhibitory effect on biomass. Therefore, the optimization of culture conditions was performed to further enhance carotenoid accumulation, including high light stress (10,000 lx) and the two-stage cultivation comprising 1-aminocyclopropane-1-carboxylic acid (ACC) and FA. Under both culture conditions, the growth inhibition caused by FA was alleviated, leading to a further increase in the contents of chlorophylls and carotenoids. HPLC analysis revealed that the production of lutein, α-carotene and β-carotene increased by 0.44-, 0.37- and 0.54-fold under the treatment of 400 mg/L FA with high light intensity and 0.91-, 1.15- 0.29-fold under the two-stage cultivation comprising 11 mM ACC and 500 mg/L FA. Furthermore, algal cells under FA treatment and the two-stage cultivation stained with Bodipy505/515 emitted stronger fluorescence under a laser confocal microscope, suggesting that lipid accumulation was increased. Additionally, the transcription levels of carotenogenic genes were also found to be up-regulated by qRT-PCR. These results indicated an enhancement in both the storage capacity and synthesis of carotenoids in D. bardawil. This study revealed the potential application of plant growth regulators in promoting carotenoid accumulation in D. bardawil which could be further improved by optimizing the culture conditions, providing a reference for efficient carotenoid production in microalgae.

A Chimeric Peptide for Shielding Plant Photosynthetic Systems against Excess Light Stress via Chloroplast-Targeted ROS Quenching

A Chimeric Peptide for Shielding Plant Photosynthetic Systems against Excess Light Stress via Chloroplast-Targeted ROS Quenching

Response of Native and Non-Native Subarctic Plant Species to Continuous Illumination by Natural and Artificial Light.

This study addressed the following questions: How does continuous lighting (CL) impact plant physiology, and photosynthetic and stress responses? Does the impact of CL depend on the source of the light and other environmental factors (natural vs. artificial)? Do responses to CL differ for native and non-native plant species in the subarctic region and, if differences exist, what physiological reasons might they be associated with them? Experiments were conducted with three plants native to the subarctic region (Geranium sylvaticum L., Geum rivale L., Potentilla erecta (L.) Raeusch.) and three non-native plant species (Geranium himalayense Klotzsch, Geum coccineum Sibth. and Sm., Potentilla atrosanguinea Loddiges ex D. Don) introduced in the Polar-Alpine Botanic Garden (KPABG, 67°38' N). The experimental groups included three species pairs exposed to (1) a natural 16 h photoperiod, (2) natural CL, (3) an artificial 16 h photoperiod and (4) artificial CL. In the natural environment, measurements of physiological and biochemical parameters were carried out at the peak of the polar day (at the end of June), when the plants were illuminated continuously, and in the second week of August, when the day length was about 16 h. Th experiments with artificial lighting were conducted in climate chambers where plants were exposed to 16 h or 24 h photoperiods for two weeks. Other parameters (light intensity, spectrum composition, temperature and air humidity) were held constant. The obtained results have shown that plants lack specific mechanisms of tolerance to CL. The protective responses are non-specific and induced by developing photo-oxidative stress. In climate chambers, under constant environmental conditions artificial CL causes leaf injuries due to oxidative stress, the main cause of which is circadian asynchrony. In nature, plants are not photodamaged during the polar day, as endogenous rhythms are maintained due to daily fluctuations of several environmental factors (light intensity, spectral distribution, temperature and air humidity). The obtained data show that among possible non-specific protective mechanisms, plants use flavonoids to neutralize the excess ROS generated under CL. In local subarctic plants, their photoprotective role is significantly higher than in non-native introduced plant species.

PGPR alleviated the negative effects of low temperature and low light stress on the growth and physiology of violet plants

Plants in greenhouses are often exposed to low temperature and low light conditions in the winter, and this has a major effect on flower cultivation. Inoculation of plant growth-promoting rhizobacteria (PGPR) can improve the growth of plants under stress. Here, we examined the effects of Pseudomonas fluorescens on the growth, photosynthesis, chlorophyll fluorescence parameters, and antioxidant enzyme systems of violet plants (Matthiola incana) exposed to normal temperature and normal light intensity (18 °C/11 °C, 500 μmol·m-2·s-1, NN), low temperature and normal light intensity (4 °C/1 °C, 500 μmol·m-2·s-1, LN), normal temperature and low light intensity (18 °C/11°C, 100 μmol·m-2·s-1, NL), and low temperature and low light intensity (4 °C/1 °C, 100 μmol·m-2·s-1, LL). The results showed that the plant height, stem diameter, leaf area, shoot fresh/dry weight, and underground fresh/dry weight of violet inoculated with PGPR were 40%, 17%, 13%, 25%, 41%, 30%, and 38% higher than the control, respectively. In addition, the total root length, mean root diameter, number of root tips, number of bifurcated root tips, and root vigor were 24%, 23%, 14%, 30%, and 21% higher in the inoculated group than in the control group, respectively. PGPR promoted chlorophyll accumulation in plants, and the net photosynthetic rate of violets was 32% higher in plants inoculated with PGPR than in control plants. PGPR also significantly promoted the maximum photochemical conversion efficiency of photosystem II (PSII) and the potential activity of PSII under UV light. After inoculation with PGPR, the content of MDA decreased by 16.8%, and the activities of superoxide dismutase and peroxidase increased by 19.2% and 20.0%, respectively. Therefore, PGPR can promote the growth of violet plants by increasing the photosynthetic capacity, activating the antioxidant enzyme system, and reducing damage induced by exposure to low light intensity.

Photoinhibition and recovery of primary photosynthesis in Antarctic and subantarctic lichens. Analysis of interspecific differences

This study meticulously investigates the dynamics of photoinhibition and the mechanisms of primary photosynthetic activity recovery in lichens found in Antarctica and the sub-Antarctic regions. Advanced methodologies were utilised, such as Kautsky's kinetic analysis and the OJIP test. The study carefully details the response of various lichen species to intense light stress, outlining both immediate effects and subsequent recovery processes. Our findings reveal that these lichens employ a range of adaptive strategies, specific to each species, to mitigate the effects of photoinhibition, thereby emphasizing their remarkable resilience and ecological importance in harsh environments. Notably, the investigation reveals the sophisticated interplay between inherent photoprotective mechanisms and the ecological adaptations that enable these lichens to thrive under such harsh conditions. The study not only advances our knowledge of plant physiology under stress but also enriches our insights into the survival strategies of terrestrial organisms facing global environmental changes. Three types of photoinhibitory treatments differing in their duration and strength were applied to 7 lichen species from Antarctica and South America (Isla Navarino). The lichens responded with a decrease in photosynthetic processes in photosystem II (FV/FM and ΦPSII declined), although they showed almost complete recovery in the following 5 h. This was attributed to the activation of photoprotective mechanisms, non-photochemical quenching (NPQ) in particular, during photoinhibitory treatments. Chlorophyll fluorescence parameters derived from slow Kautsky kinetics were correlated with those derived from the OJIP curve. Our study presents data that supports the conclusion of significant photoresistance of the studied lichen species in the hydrated state to photoinhibition induced by high doses of photosynthetically active radiation (PAR).

Polyunsaturated triacylglycerol accumulation mainly attributes to turnover of de novo-synthesized membrane lipids in stress-induced starchless Chlamydomonas.

Assembly of PUFA-attached TAGs is intimately correlated to turnover of newly formed membrane lipids in starch-deficient Chlamydomonas exposed to high light and nitrogen stress under air-aerated mixotrophic conditions. Triacylglycerols (TAGs) rich in polyunsaturated fatty acids (PUFAs) in microalgae have attracted extensive attention due to its promising application in nutraceuticals and other high-value compounds. Previous studies revealed that PUFAs accumulated in TAG primarily derived from the dominant membrane lipids, monogalactosyldiacylglycerolipid, digalactosyldiacylglycerol and diacylglycerol-N,N,N-trimethylhomoserine (DGTS), in the model alga Chlamydomonas reinhardtii. However, their respective contribution to PUFA-attached TAG integration has not been clearly deciphered, particularly in starchless Chlamydomonas that hyper-accumulates TAG. In this study, the starchless C. reinhardtii BAFJ5 was mixotrophically cultivated in photobioreactors aerated with air (0.04% CO2), and we monitored the dynamic changes in growth, cellular carbon and nitrogen content, photosynthetic activity, biochemical compositions, and glycerolipid remodeling under high light and nitrogen starvation conditions. The results indicated that multiple PUFAs continually accumulated in total lipids and TAG, and the primary distributors of these PUFAs gradually shifted from membrane lipids to TAG in stress-induced BAFJ5. The stoichiometry analyses showed that the PUFA-attached TAG assembly attributed to turnover of not only the major glycerolipids, but also the phospholipids, phosphatidylethanolamine (PE) and phosphatidylglycerol. Specifically, the augmented C16:3n3 and C18:3n3 in TAG mainly originated from de novo-synthesized galactolipids, while the cumulative C18:3n6 and C18:4n3 in TAG were intimately correlated with conversion of the newly formed DGTS and PE. These findings emphasized significance of PUFA-attached TAG formation dependent on turnover of de novo assembled membrane lipids in starch-deficient Chlamydomonas, beneficial for enhanced production of value-added lipids in microalgae.

Genome-wide identification and expression analyses of SWEET gene family reveal potential roles in plant development, fruit ripening and abiotic stress responses in cranberry (Vaccinium macrocarpon Ait).

The sugars will eventually be exported transporter (SWEET) family is a novel class of sugar transporters that play a crucial role in plant growth, development, and responses to stress. Cranberry (Vaccinium macrocarpon Ait.) is a nutritious berry with economic importance, but little is known about SWEET gene family functions in this small fruit. In this research, 13 VmSWEET genes belonging to four clades were identified in the cranberry genome for the first time. In the conserved domains, we observed seven phosphorylation sites and four amino acid residues that might be crucial for the binding function. The majority of VmSWEET genes in each clade shared similar gene structures and conserved motifs, showing that the VmSWEET genes were highly conserved during evolution. Chromosomal localization and duplication analyses showed that VmSWEET genes were unevenly distributed in eight chromosomes and two pairs of them displayed synteny. A total of 79 cis-acting elements were predicted in the promoter regions of VmSWEETs including elements responsive to plant hormones, light, growth and development and stress responses. qRT-PCR analysis showed that VmSWEET10.1 was highly expressed in flowers, VmSWEET16 was highly expressed in upright and runner stems, and VmSWEET3 was highly expressed in the leaves of both types of stems. In fruit, the expression of VmSWEET14 and VmSWEET16 was highest of all members during the young fruit stage and were downregulated as fruit matured. The expression of VmSWEET4 was higher during later developmental stages than earlier developmental stages. Furthermore, qRT-PCR results revealed a significant up-regulation of VmSWEET10.2, under osmotic, saline, salt-alkali, and aluminum stress conditions, suggesting it has a crucial role in mediating plant responses to various environmental stresses. Overall, these results provide new insights into the characteristics and evolution of VmSWEET genes. Moreover, the candidate VmSWEET genes involved in the growth, development and abiotic stress responses can be used for molecular breeding to improve cranberry fruit quality and abiotic stress resistance.

Transcriptomic Analysis Provides New Insights into the Tolerance Mechanisms of Green Macroalgae Ulva prolifera to High Temperature and Light Stress.

Our research focused on understanding the genetic mechanisms that contribute to the tolerance of Ulva prolifera (Chlorophyta), a marine macroalgae, to the combined stress of high temperature and high light intensity. At the mRNA level, the up-regulated DEGs showed enrichment in pathways related to ribosomes, proteasomes, and peroxisomes. The spliceosome pathway genes were found to be vital for U. prolifera's ability to adapt to various challenging situations in all the comparison groups. In response to elevated temperature and light intensity stress, there was a significant increase in genes and pathways related to ribosomes, proteasomes, and peroxisomes, whereas autophagy showed an increase in response to stress after 24 h, but not after 48 h. These findings provide novel insights into how U. prolifera adapts to elevated temperature and light stress.

Controllable Iodoplumbate-Coordination of Hybrid Lead Iodide Perovskites via Additive Engineering for High-Performance Solar Cells.

The crystallization and growth of perovskite crystals are two crucial factors influencing the performance of perovskite solar cells (PSCs). Moreover, iodoplumbate complexes such as PbI2, PbI3-, and PbI42- in perovskite precursor solution dictate both the quality of perovskite crystals and the optoelectrical performance of PSCs. Here, we propose an iodoplumbate-coordination strategy that employs pentafluorophenylsulfonyl chloride (PTFC) as an additive to tailor the crystal quality. This strategy directly affects the thermodynamics and kinetics of perovskite crystal formation by regulating hydrogen bonds or coordination bonds with Pb2+ or I- ions. Subsequently, the synergistic effect of the PTFC and FA+ complex was beneficial for intermediate-to-perovskite phase transition, improving the crystalline quality and reducing the defect density in the perovskite film to suppress nonradiative recombination loss. Consequently, the treated PSCs achieved a power conversion efficiency (PCE) of 24.61%, demonstrating enhanced long-term stability under both light and thermal stress. The developed device retained 92.53% of its initial PCE after 1200 h of continuous illumination and 88.6% of its initial PCE after 600 h of 85 °C thermal stability tests, respectively, both conducted in N2 atmospheres.

Use microfluidics to study cell migration in response to fluid shear stress gradients

Cells respond not only to biological regulatory factors but also to physical stimuli such as electric fields, light, and shear stress in their environment. These stimuli can lead to cell migration and morphological changes. In the human body, cells encounter fluid shear stress induced by interstitial flow, lymphatic flow, blood flow, or organ-specific conditions within their micro-environments. Therefore, fluid shear stress, a classic mechanical force, has gained significant attention in wound healing and cancer metastasis. In this study, a microfluidic chip was developed to both culture cells and generate a shear stress gradient to direct cell migration. The design of this device’s geometry allows the generation of a shear stress gradient perpendicular to the direction of medium flow. This greatly eliminates the influence of flow-induced cell responses. Using mouse fibroblast cells (NIH3T3) and human lung cancer cells (CL1-5) as models, their migration directionality, migration rates, and alignment in response to the shear stress gradient were investigated. Within the stress range of 0.095–0.155 Pa and a gradient of 0.015 Pa/mm, NIH3T3 cells did not exhibit significant directional migration, differences in migration rates, or specific alignment patterns. In contrast, CL1-5 cells preferred higher shear stress environments and alignment parallel to the medium flow, suggesting that these conditions could induce higher mobility in these cancer cells.

Nanoarchitectonics in Macromolecular Science: Integrating Molecular Dynamics with Smart Materials

Nanoarchitectonics represents a transformative approach in macromolecular science, extending beyond traditional nanotechnology by emphasizing the precise design and construction of complex materials through controlled molecular interactions. This review explores the integration of nanoarchitectonics with molecular dynamics, a powerful computational tool that enables the prediction and optimization of material behavior at the atomic level. The synergy between these two fields allows for the rational design of smart materials that respond dynamically to environmental stimuli, such as temperature, light and mechanical stress. These materials, including thermo-responsive hydrogels, photochromic polymers and self-healing coatings, demonstrate the significant potential of nanoarchitectonics in creating materials with tailored properties for diverse applications. By leveraging molecular dynamics, researchers can gain insights into the energy landscapes and interaction patterns that drive the self-assembly and functionality of these materials, leading to enhanced performance and novel functionalities. This review also examines the future perspectives of nanoarchitectonics, highlighting the potential of integrating artificial intelligence and machine learning with it to further revolutionize material design. As the field advances, the combination of nanoarchitectonics and molecular dynamics is expected to unlock new possibilities in macromolecular science, offering innovative solutions for applications ranging from biomedical devices to environmental remediation. The review concludes by discussing the challenges and opportunities in translating these innovations from the laboratory to real-world applications, emphasizing the need for interdisciplinary collaboration to fully realize the potential of nanoarchitectonic materials in addressing global challenges.

Effect of phytohormones on the carbon sequestration performance of CO2 absorption-microalgae conversion system under low light restriction

Microalgae have the potential to fix CO2 into valuable compounds. Low photosynthetic efficiency caused by low light was one of the challenges faced by microalgae carbon sequestration. In this study, Melatonin (MT) and indole-propionic acid (IPA) were used to alleviate the growth inhibition of Spirulina in CAMC system under low light restriction. The results showed that MT and IPA increased biomass and carbon fixation capacity. 10 mg/L IPA group achieved the maximum biomass and carbon fixation capacity, which were 17.11% and 21.46% higher than control. MT and IPA promoted the synthesis of chlorophyll, which in turn captured more light energy for microalgae growth. The increase of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) activities enhanced the resistance of microalgae to low light stress. MT and IPA promoted the secretion of extracellular polymeric substances (EPS) which was benefit to protect cells. The maximum phycocyanin content and yield was found in 10 mg-IPA group, which was 20.67% and 46.67% higher than control. MT and IPA improved the synthesis of carbohydrates and proteins and increased carbohydrates and proteins yield. This indicated that adding phytohormones was an effective method to alleviate the growth of microalgae restricted by low light stress, which provided a theoretical guidance for the application of CAMC system in CO2 capture and resource utilization.

The Vital Role of the CAMTA Gene Family in Phoebe bournei in Response to Drought, Heat, and Light Stress.

The calmodulin-binding transcriptional activator (CAMTA) is a small, conserved gene family in plants that plays a crucial role in regulating growth, development, and responses to various abiotic stress. Given the significance of the CAMTA gene family, various studies have been dedicated to uncovering its functional characteristics. In this study, genome-wide identification and bioinformatics analysis were conducted to explore CAMTAs in Phoebe bournei. A total of 17 CAMTA genes, each containing at least one domain from CG-1, TIG, ANK, or IQ, were identified in the P. bournei genome. The diversity of PbCAMTAs could be varied depending on their subcellular localization. An analysis of protein motifs, domains, and gene structure revealed that members within the same subgroup exhibited similar organization, supporting the results of the phylogenetic analysis. Gene duplications occurred among members of the PbCAMTA gene family. According to the cis-regulatory element prediction and protein-protein interaction network analysis, eight genes were subjected to qRT-PCR under drought, heat, and light stresses. The expression profiles indicated that PbCAMTAs, particularly PbCAMTA2, PbCAMTA12, and PbCAMTA16, were induced by abiotic stress. This study provides profound insights into the functions of CAMTAs in P. bournei.

Genomic Organization and Expression Profiling of GOLDEN2-like Transcription Factor Genes in Eggplant and Their Role in Heat Stresses

GOLDEN2-like (GLK) transcription factor genes are involved in chloroplast biogenesis during all stages of plant growth and development, as well as in the response to biotic and abiotic stresses. However, little is known about this transcription factor family in eggplant. In this study, we identified 54 GLK genes in the eggplant genome (S. melongena L.) and classified them into seven groups (G1–G7). Structural analysis illustrated that the SmGLK proteins of specific groups are relatively conserved. Cis-acting elements indicated that these genes are likely to be involved in multiple responses stimulated by light, phytohormones, and abiotic stress. Collinear analysis indicated that expansion of the SmGLK gene family primarily occurred through segmental duplication. Tissue-specific expression analysis revealed that SmGLKs were preferentially expressed in leaves, fruits, and seeds. Further screening of SmGLK genes revealed their differential expression under various treatments. Notably, SmGLK18 was significantly responsive to multiple phytohormones and stress treatments, whereas SmGLK3 and SmGLK12 were highly induced by ABA, IAA, SA, and drought treatments. Our study provides new information on the eggplant GLK family systematically and comprehensively. For the first time, we propose that SmGLK18 may play a key role in improving heat resistance. This study provides valuable candidate gene resources for further functional research and will benefit eggplant molecular breeding.

Enhancement of Forskolin Production Using Aeroponic Cultivation of Coleus forskohlii and the Impact on the Plant Phytochemistry.

Accessing plant resources to extract compounds of interest can sometimes be challenging. To facilitate access and limit the environmental impact, innovative cultivation strategies can be developed. Forskolin is a molecule of high interest, mainly found in the roots of Coleus forskohlii. The aim of this study was to develop aeroponic cultivation methods to provide a local source of Coleus forskohlii and to study the impact of abiotic stress on forskolin and bioactive metabolite production. Three cultivation itineraries (LED lighting, biostimulant, and hydric stress) along with a control itinerary were established. The forskolin content in the plant roots was quantified using HPLC-ELSD, and the results showed that LED treatment proved to be the most promising, increasing root biomass and the total forskolin content recovered at the end of the cultivation period threefold (710.1 ± 21.3 mg vs. 229.9 ± 17.7 mg). Statistical analysis comparing the LED itinerary to the control itinerary identified stress-affected metabolites, showing that LEDs positively influence mainly the concentration of phenolic compounds in the roots and diterpenes in the aerial parts of Coleus forskohlii. Moreover, to better define the phytochemical composition of Coleus forskohlii cultivated in France using aeroponic cultivation, an untargeted metabolomic analysis was conducted using UHPLC-HRMS/MS analysis and molecular networks on both the root and aerial parts. This study demonstrates that aeroponic cultivation, especially with the application of an LED treatment, could be a very promising alternative for a local source of Coleus forskohlii leading to easy access to the roots and aerial parts rich in forskolin and other bioactive compounds.

Genome-wide analysis of the WOX gene family and function exploration of RhWOX331 in rose (R. 'The Fairy').

WOXs are a class of plant-specific transcription factors that play key roles in plant growth and stress responses. However, the mechanism by which WOXs influence adventitious root development in Rosa hybrida remains unclear. In this study, RcWOX gene family in rose was identified and phylogenetically analyzed using bioinformatics analysis. A total of 381 RcWOX gene members were localized on seven chromosomes except of nine members. The main cis-acting elements involved in hormonal, light, developmental, and abiotic stress responses were identified in the promoters of RcWOX genes, suggesting their regulation by these signals. Nine RhWOX genes had significant different expression during rooting process of rose. RhWOX331, RhWOX308, RhWOX318 were positive with the formation of rose roots. RhWOX331 was positively involved in the formation of adventitious root primordia, which gene coding a transcription factor localized in the nucleus. The HOX conserved domain in the protein contributed to the self-activating activity of RhWOX331. We obtained genetically modified Arabidopsis to validate the function of RhWOX331. Overexpression of RhWOX331 gene alleviated the inhibition of root length of A. thaliana primary roots by high concentration of IBA and NPA, and significantly increased the number of lateral roots on the primary roots, as well as the height of A. thaliana plants. Additionally, RhWOX331 promoted adventitious root formation in A. thaliana and mitigated hormonal inhibition by exogenous 6-BA, NPA, and GA3. The RhWOX331 promoter contained cis-acting elements such as ABRE, Box 4 and CGTCA-motif et.al. GUS activity analysis showed that the gene acted at the cotyledon attachment site. Taken together, these studies identified a significant expansion of the RcWOX gene family, inferred roles of certain branch members in adventitious root formation, elucidated the function of RhWOX331 in adventitious root initiation, and laid the foundation for further research on the function of WOX gene family in roses.

Alternative buffer systems in biopharmaceutical formulations and their effect on protein stability.

The formulation of biopharmaceutical drugs is designed to eliminate chemical instabilities, increase conformational and colloidal stability of proteins, and optimize interfacial stability. Among the various excipients involved, buffer composition plays a pivotal role. However, conventional buffers like histidine and phosphate buffers may not always be the optimal choice for all monoclonal antibodies (mAbs). In this study, we investigated the effects of several alternative buffer systems on seven different mAbs, exploring various combinations of ionic strengths, concentrations of the main buffer component, mAb concentrations, and stress conditions. Protein stability was assessed by analyzing soluble aggregate formation through size exclusion chromatography. At low protein concentrations, protein instability after temperature stress was exclusively observed in the bis-TRIS/ glucuronate buffer. Conversely, freeze-thaw stress led to a significant increase in aggregate formation in tested formulations, highlighting the efficacy of several alternative buffers, particularly arginine/ citrate, in preserving protein stability. Under temperature stress, the introduction of arginine to histidine buffer systems provided additional stabilization, while the addition of lysine resulted in protein destabilization. Similarly, the incorporation of arginine into histi-dine/HCl buffer further enhanced protein stability during freeze--thaw cycles. At high protein concentrations, the histidine/citrate buffer emerged as one of the most optimal choices for addressing temperature and light-induced stress. The efficacy of histidine buffers in combating light stress might be attributed to the light-absorbing properties of histidine molecules. Our findings demonstrate that the development of biopharmaceutical formulations should not be confined to conventional buffer systems, as numerous alternative options exhibit comparable or even superior performance.

Phytohormones enhanced carbon fixation and biomass production in CO2 absorption-microalgae conversion system under light stress

CO2 absorption-microalgae conversion (CAMC) system can be a sustainable technology to achieve low-energy carbon capture and resource utilization in response to zero carbon. However, light stress could restrict the carbon utilization efficiency of CAMC system. In this study, melatonin (MT) and indole-propionic acid (IPA) as phytohormones, were used to promote the carbon fixation capacity and biomass yield of CAMC system under light stress, and the potential mechanism was also discussed. Both MT and IPA promoted the growth of Spirulina, and 10 mg-MT group obtained the highest biomass and carbon fixation capacity, which were 27.61 % and 30.62 % higher than control. MT and IPA promoted the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), enhancing antioxidant activity to avoid oxidative damage. The results of transmission electron microscopy (TEM) and cell apoptosis showed MT and IPA reduced cell membrane damage and apoptosis. Phytohormones induced the carbon flux flow to the synthesis of carbohydrate and protein, and increased carbohydrate and protein productivity. Moreover, the maximum phycocyanin content and yield were 13.74 % and 43.25 % higher than the control. Therefore, adding phytohormones was an effective strategy to achieve high-value bioresources of microalgae in CAMC system under light stress.

Green Leaf Volatiles: A New Player in the Protection against Abiotic Stresses?

To date, the role of green leaf volatiles (GLVs) has been mainly constrained to protecting plants against pests and pathogens. However, increasing evidence suggests that among the stresses that can significantly harm plants, GLVs can also provide significant protection against heat, cold, drought, light, and salinity stress. But while the molecular basis for this protection is still largely unknown, it seems obvious that a common theme in the way GLVs work is that most, if not all, of these stresses are associated with physical damage to the plants, which, in turn, is the major event responsible for the production of GLVs. Here, I summarize the current state of knowledge on GLVs and abiotic stresses and provide a model explaining the multifunctionality of these compounds.

Species-specific effects of light and temperature on photosynthesis and respiration among Symbiodiniaceae (Dinophyceae)

Coral reefs are exposed to various environmental stressors that cause bleaching events, whereby endosymbiotic microalgae (Symbiodiniaceae) disassociate from coral hosts. Bleached corals are compromised and face mortality. The combination of high-light exposure and elevated seawater temperature often lead to coral bleaching. The physiological properties of the Symbiodiniaceae within the coral tissues contribute to the thermal tolerance of the holobiont (the host and all its symbionts). The present study aimed to investigate the effects of light and temperature stress on four Symbiodiniaceae species from three genera with respect to photosynthetic oxygen production and consumption. Under control conditions, the species displayed predominantly low-to-moderate light requirements for photosynthesis with increased photoinhibition at higher photon flux rates. After 30 days of heat acclimation at 32 °C, maximum photosynthetic activity declined in Effrenium voratum, doubled in Fugacium kawagutii, and remained unchanged in Breviolum psygmophilum. In subsequent acute heating assays, species-specific effects on maximum photosynthetic activity were observed. Photosynthesis in all species declined across a temperature gradient between 25 and 39 °C in the acute heating assays; full inhibition occurred at 37 °C in B. psygmophilum and E. voratum and at 39 °C in B. aenigmaticum and F. kawagutii. In contrast, respiration remained largely constant in all species across temperatures. Our data point to species-specific photophysiological traits that lead to different thermal tolerances among Symbiodiniaceae.