Combination Of Stress Factors Research Articles

Using In Vitro Cultured Berries to Unravel the Effects of Heat- and ABA-Induced Stress on Thiol Precursor Biosynthesis in Sauvignon Blanc.

Global warming, heat waves, and seasonal drought pose serious threats to crops, such as grapevine, that are valued for their secondary metabolites, which are of primary importance for the wine industry. Discriminating the effects of distinct environmental factors in the open field is challenging. In the present study, in vitro cultured berries of Sauvignon Blanc were exposed to individual and combined stress factors to investigate the effects on the biosynthesis of the thiol precursors. Our results confirm the complexity and extreme reactivity of the accumulation process in grapes. However, they also indicate that heat stress has a positive effect on the production of the Cys-3SH precursor. Moreover, we identified several candidate genes, such as VvGSTs and VvGGT that are potentially involved in biosynthesis and consistently modulated. Nonetheless, we were unable to conclusively determine the effects of stresses on the biosynthesis of other precursors nor could we formulate hypotheses regarding their regulation.

A Physiological and Molecular Focus on the Resistance of "Filippo Ceo" Almond Tree to Xylella fastidiosa.

The impact of Xylella fastidiosa (Xf) subsp. pauca on the environment and economy of Southern Italy has been devastating. To restore the landscape and support the local economy, introducing new crops is crucial for restoring destroyed olive groves, and the almond tree (Prunus dulcis Mill. D. A. Webb) could be a promising candidate. This work focused on the resistance of the cultivar "Filippo Ceo" to Xf and evaluated its physiological and molecular responses to individual stresses (drought or pathogen stress) and combined stress factors under field conditions over three seasons. Filippo Ceo showed a low pathogen concentration (≈103 CFU mL-1) and a lack of almond leaf scorch symptoms. Physiologically, an excellent plant water status was observed (RWC 82-89%) regardless of the stress conditions, which was associated with an increased proline content compared to that of the control plants, particularly in response to Xf stress (≈8-fold). The plant's response did not lead to a gene modulation that was specific to different stress factors but seemed more indistinct: upregulation of the LEA and DHN gene transcripts by Xf was observed, while the PR transcript was upregulated by drought stress. In addition, the genes encoding the transcription factors (TFs) were differentially induced by stress conditions. Filippo Ceo could be an excellent cultivar for coexistence with Xf subps. pauca, confirming its resistance to both water stress and the pathogen, although this similar health status was achieved differently due to transcriptional reprogramming that results in the modulation of genes directly or indirectly involved in defence strategies.

Functional trait correlation network and proteomic analysis reveal multifactorial adaptation mechanisms to a climatic gradient associated with high altitude in the Himalayan region.

Globally occurring changes in environmental conditions necessitate extending our knowledge of the system-level mechanisms underlying plant adaptation to multifactorial stress conditions or stress combinations. This is crucial for designing new strategies to maintain plant performance under simultaneous abiotic pressure. Here, we conducted our study at Rohtang Pass and sampled Picrorhiza kurroa leaves along high-altitude gradient (3400, 3800 and 4100 metersabove sea level) in the western Himalayas. The results showed the functional traits associated with morpho-anatomical structures and eco-physiological performances are highly variable. The air temperature and relative humidity represent dominant environmental factors among others that significantly regulate plant's physiological performance by adjusting the functional traits in altitude-specific manner. A trait coordination network is developed among significantly altered plant functional traits, which reveals high-altitude associated trait-based adaptation. Moreover, it reveals leaf area shows the highest degree, while photochemical quenching reflects the weighted degree of centrality in the network. Proteomic analysis reveals various stress-responsive proteins, including antioxidants were accumulated to deal with combined stress factors. Furthermore, a high-altitudinal protein interaction network unravels key players of alpine plant adaptation processes. Altogether, these systems demonstrate a complex molecular interaction web extending the current knowledge of high-altitudinal alpine plant adaptation, particularly in an endangered medicinal herb, P. kurroa.

The interaction between titanium dioxide nanoparticles and light can have dualistic effects on the physiological responses of plants.

The model plant Arabidopsis thaliana was exposed to combined stress factors, i.e., titanium dioxide nanoparticles (TiNPs) and high light. The concentrations of TiNPs used for irrigation were 250, 500, and 1000μg/mL. This study shows that TiNPs alter the morphology and nanomechanical properties of chloroplasts in A. thaliana, which leads to a decrease in membrane elasticity. We found that TiNPs contributed to a delay in the thermal response of A. thaliana under dynamic light conditions, as revealed by non-invasive thermal imaging. The thermal time constants of TiNP-treated plants under excessive light are determined, showing a shortening in comparison to control plants. The results indicate that TiNPs may contribute to an alleviation of temperature stress experienced by plants under exposure to high light. In this research, we observed a decline in photosystem II photochemical efficiency accompanied by an increase in energy dissipation upon exposure to TiNPs. Interestingly, concentrations exceeding 250µg/mL TiNPs appeared to mitigate the effects of high light, as shown by reduced differences in the values of specific OJIP parameters (FV/FM, ABS/RC, DI0/RC, and Pi_Abs) before and after light exposure.

Resilience of Xanthoria parietina under Mars-like conditions: photosynthesis and oxidative stress response.

Xanthoria parietina survivability in Mars-like conditions was supported by water-lysis efficiency recovery and antioxidant content balancing with ROS production after 30days of exposure. Xanthoria parietina (L.) Th. Fr. is a widespread lichen showing tolerance against air pollutants and UV-radiation. It has been tested under space-like and Mars-like conditions resulting in high recovery performances. Hereby, we aim to assess the mechanisms at the basis of the thalli resilience against multiple space stress factors. Living thalli of X. parietina were exposed to simulated Martian atmospheric conditions (Dark Mars) and UV radiation (Full Mars). Then, we monitored as vitality indicator the photosynthetic efficiency, assessed by in vivo chlorophyll emission fluorescence measurements (FM; FV/F0). The physiological defense was evaluated by analyzing the thalli antioxidant capacity. The drop of FM and FV/F0 immediately after the exposure indicated a reduction of photosynthesis. After 24h from exposure, photosynthetic efficiency began to recover suggesting the occurrence of protective mechanisms. Antioxidant concentrations were higher during the exposure, only decreasing after 30days. The recovery of photosynthetic efficiency in both treatments suggested a strong resilience by the photosynthetic apparatus against combined space stress factors, likely due to the boosted antioxidants at the beginning and their depletion at the end of the exposure. The overall results indicated that the production of antioxidants, along with the occurrence of photoprotection mechanisms, guarantee X. parietina survivability in Mars-like environment.

Bi-parameter thermal-mechanical reliability of miniaturised electromechanical RF relays for space applications

Reliability assessment of the miniaturised RF electromechanical relays under the simultaneously applied thermal and mechanical stresses was studied. This combination of stress factors, commonly overseeing by the existing reliability standards and testing procedures, does occur in certain operation conditions, such as during the spacecraft launch phase. It was demonstrated that the relay robustness for the mechanical vibration is not affected by high temperature up to the maximum device operation T of 100 °C. However, a progressive deterioration of the device performance under mechanical shocks with the temperature increase was observed. The relay exhibits state flipping events at lower shock accelerations under high temperatures. The relay's destruction limits are also lower at the maximum device operation temperature. The observed degradation is not large, and the device performance stays within the required specifications even at the highest operation temperature.

Study on toxicity responses and their mechanisms in Xenopus tropicalis long-term exposure to Shigella flexneri and ciprofloxacin

The abuse and overuse of antibiotics increased not only the exposure of aquatic animals to antibiotics but also the development of resistance in pathogenic bacteria. To investigate the effects and mechanisms of exposure, a long-term experiment lasting 120 days was conducted in which Xenopus tropicalis was exposed to single and combined stress factors of multiresistant pathogenic Shigella flexneri and ciprofloxacin (CIP). The intestinal oxidative stress, immune factors and flora, as well as the brain-gut axis correlation factors of X. tropicalis, were tracked to account for the response of aquatic animals to the exogenous pollutants. SOD activity and MDA content were significantly increased in stressed X. tropicalis (p < 0.001), while the levels of proinflammatory factors (IL-1β, IFN-γ) were significantly reduced (p < 0.01). The content of intestinal beneficial bacteria decreased and that of harmful bacteria increased in the intestinal flora of the stressed X. tropicalis (p < 0.001). These results suggested that S. flexneri and CIP disturbed the intestinal flora and caused oxidative damage in the host, and the body produced a series of responses, such as oxidative stress responses and regulation of the expression of immune factors, to maintain the balance of antioxidant inflammation. Significant changes in the expression of intestinal neurotransmitters (5-HT, CGRP) and brain peptides (BDNF, NCAM, NPY) (p < 0.05) also indicated that the brain-gut axis interaction was disrupted. In addition, although the coexisting CIP could reduce intestinal toxicity caused by S. flexneri, the amount of intestinal pathogenic bacteria Desulfovibrio increased significantly. Moreover, compared with the single exposure group, SOD activity, CAT activity and MDA content were significantly reduced in the dual exposure group. Therefore, the health risks of multiresistant pathogenic bacteria on the intestinal and brain-gut axis interaction should be given more attention, and the interaction of brain-gut axis is more important when antibiotics coexist.

Combined Phosphorus and Water stress Conditions Induce Negative Mycorrhizal Response in Maize (Zea mays L.)

Arbuscular mycorrhizal fungi (AMF) confer both positive and negative effects on the plant symbionts, depending on the prevailing growth condition. We investigated the effect of concurrent variations in phosphorus and soil moisture on percentage root colonization (%RC), mycorrhizal growth response (MGR) and drought response index (DRI) of SAMMAZ-16 maize variety in timescale. The experimental factors were AMF inoculation (addition or no addition), P2O5 applications (30, 60 or 90 kg ha-1) and water regimes (100% and 50% of the soil’s field capacity introduced after 4WAS). The result shows that the overall %RC was 62.22% at 8 weeks after sowing (WAS) and 71.33% at 12 WAS. With 30 and 60 kg P2O5 ha-1 application a rate, %RC was significantly higher at 12 WAS than that of similar application rates at 8 WAS. However, %RC was not different between 8 WAS and 12 WAS in 90 kg P2O5 ha-1 application. AMF inoculation tended to equilibrate the shoot growth of the inoculated plants to that of non- inoculated plants that received 50% higher doses of P2O5 under amply watered conditions. Increasing phosphorus application progressively alleviated the negative mycorrhizal response of the plants at the early stage of growth (week 4) and in 50% FC category at the other sampling times. Higher doses of P2O5 application improved the DRI of the maize in both samplings but the trend was more consistent in AMF-inoculated plants. We conclude that AMF inoculation would be detrimental to the growth of SAMMAZ-16 when there is combined phosphorus and water stress factors

Co-production of high density biomass and high-value compounds via two-stage cultivation of Chlorella vulgaris using light intensity and a combination of salt stressors

In this study, the effects of combined stress factors involving light intensity and salinity (NaCl, MgCl2, CaCl2, and their combinations) on the two-stage cultivation of Chlorella vulgaris for simultaneous production of biomass and high-value products, were investigated. The two-stage strategies comprised a 25-day vegetative stage in BG11 medium, followed by a 15-day combined stress stage. During salt stress conditions, the addition of 15 g L−1 CaCl2 or 7.5 g L−1 MgCl2 / 7.5 g L−1 CaCl2 mixture with 140 µmol m−2 s−1 light intensity significantly promoted the growth of C. vulgaris achieving maximum biomass productivity of 50.50 ± 0.50 and 50.25 ± 3.25 mg L−1 d−1, respectively. Cultivation of C. vulgaris in a medium containing 7.5 g L−1 NaCl/ 7.5 g L−1 CaCl2 had remarkably increased the lipid content (31.15 ± 1.18%) and lipid productivity (14.55 ± 1.48 mg L−1 d−1). The saturated fatty acids (SFAs) at 39.52–59.29%, monounsaturated fatty acids (MUFAs) at 27.16–35.47%, and polyunsaturated fatty acids (PUFAs) at 7.18–29.97%, were obtained with palmitic (C16:0), oleic (C18:1), stearic (C18:0), and linolenic (C18:3) acids as predominant fatty acids. Cultures supplemented with 5 g L−1 NaCl / 5 g L−1 MgCl2 / 5 g L−1 CaCl2 and high light intensity exposure attained consistently high carbohydrate content (52.71 ± 2.50%). The combination of 7.5 g L−1 NaCl / 7.5 g L−1 MgCl2 also resulted in a marked increase in the protein content (35.32 ± 2.20%) and total carotenoids (0.31 ± 0.03 μg mL−1) as compared to the Controls. The highest antioxidant activity (86.16%) was achieved with a 7.5 g L−1 NaCl / 7.5 g L−1 CaCl2 combination in the growth stage. The antioxidant activities were attributed to the presence of phenolics, flavonoids, and tannins due to the stressed conditions. One of the key benefits of using a combined stress strategy in this study is that if one factor has a low impact on enhancing target metabolites, other factors can compensate.

Effect of the Mode of Fermentation on the Behavior of Penicillium bilaiae in Conditions of Abiotic Stress.

The ability of a Penicillium bilaiae strain to support acid production and simultaneously solubilize inorganic sources of phosphate in conditions of submerged, solid-state fermentation (SSF) and immobilized cell system was examined in this study. Abiotic stress factors such as NaCl and different values of pH were introduced into the different fermentation process schemes to measure the fungal response. The results showed a higher tolerance of P. bilaiae when the fermentation process was carried out in solid-state and immobilized-cell conditions, which mimics the natural state of the soil microorganisms. The acidic culture conditions were not found to be suitable for fungal growth, which increased at a higher pH, with values of 4.0 and 6.0 being optimal for all types of fermentation. The presence of increasing amounts of NaCl provoked low biomass growth, titratable acidity, and simultaneous phosphate (P) solubilization. These results were, however, less pronounced at pH 4.0 and 6.0, particularly in conditions of SSF. Studying stress-tolerant microbial characteristics, particularly in different conditions and combinations of stress factors, is of great importance for further managing the overall microbial inoculants' production and formulation process as well as their applications in specific soil-plant systems.

Determination of cadmium and/or drought stress effects on some plant phytohormone contents and hormone gene expressions in bean (Phaseolus vulgaris L)

Plants can sometimes be under the influence of more than one stress factor. In this case, combined stress factors can cause different responses in plants. In this study, the phytohormonal activity and hormone gene expressions of beans (Phaseolus vulgaris L.) were investigated in different drought levels and soils with different levels of cadmium accumulation. Plants were grown at 4 different cadmium (Cd) levels (Cd: 0, Cd1: 100, Cd2: 150, and Cd3: 200 mg kg$^{-1}$) and 3 irrigation levels (D0: 100%, D1: 75%, and D2: 50% of field capacity). Abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid (GA), salicylic acid (SA), cytokinin, zeatin, and jasmonic acid contents and gene expressions related to them were investigated. As a result of the study, we determined that there was a significant decrease in the content of IAA, GA, SA, cytokinin, zeatin, and jasmonic acid with increasing doses of drought and Cd. Especially with the coexistence of both stress factors, this reducing effect (the reductions in these hormones were 86.6%, 64.1%, 71.9%, 66.7%, 45.5%, and 73.9% as compared to D0, respectively) on the measured parameters was greater. However, ABA content increased significantly with drought and/or Cd stresses, especially with Cd3D2, about a thousand times higher than the control. On the other hand, mRNA transcript levels of some hormone genes (ABA 8'-hydroxylase, adenylate isopentenyltransferase (AIPT3), auxin-related protein (AUX/ IAA), MeJA biosynthesis and gibberellin 20-oxidase and NRAMP2 gene known to be involved in Cd transport, were detected. According to the results, while ABA 8'-hydroxylase, gibberellin 20-oxidase, and NRAMP2 genes were overexpressed in all stress treatments, AIPT3 and AUX/IAA genes were down-regulated and also, MeJA biosynthesis gene varied depending on dose and stress.

Changes in Growth, Ionic Status, Metabolites Content and Antioxidant Activity of Two Ferns Exposed to Shade, Full Sunlight, and Salinity

The interactions between ferns and the environment have been frequently researched. However, detailed data on how ferns respond to specific stresses and a combination of stress factors during cultivation are lacking. This study assessed the effects of salinity and full sunlight and the combination of both stresses on the growth and selected metabolic parameters of two hardy ferns (Athyrium nipponicum cv. Red Beauty and Dryopteris erythrosora) under production conditions. Hardy ferns are highly interesting ornamental plants that can serve as a potential source of antioxidants for the pharmaceutical, cosmetic, and food industries. The results showed that in both ferns, salinity and salinity combined with full sunlight lowered the dry weight of the aerial part and potassium/sodium and calcium/potassium ratio compared with control plants. Salinity, full sunlight, and multi-stress did not affect the total polyphenol content in both ferns but increased the total free amino acids and flavonoids in D. erythrosora. In A. nipponicum cv. Red Beauty, all stressors decreased the total free amino acids content and the antioxidant activities determined by ABTS, DPPH, FRAP, and reducing power assays. By contrast, plants of D. erythrosora grown under full sunlight are characterized by higher antioxidant activities determined by DPPH, FRAP, and reducing power assays. Overall, a greater adaptive potential to abiotic stresses was found in D. erythrosora than in A. nipponicum cv. Red Beauty. Our findings shed some light on the physiological mechanisms responsible for sensitivity/tolerance to salinity, full sunlight, and combined stresses in hardy ferns.

To Be or Not to Be? Are Reactive Oxygen Species, Antioxidants, and Stress Signalling Universal Determinants of Life or Death?

In the environmental and organism context, oxidative stress is complex and unavoidable. Organisms simultaneously cope with a various combination of stress factors in natural conditions. For example, excess light stress is accompanied by UV stress, heat shock stress, and/or water stress. Reactive oxygen species (ROS) and antioxidant molecules, coordinated by electrical signalling (ES), are an integral part of the stress signalling network in cells and organisms. They together regulate gene expression to redirect energy to growth, acclimation, or defence, and thereby, determine cellular stress memory and stress crosstalk. In plants, both abiotic and biotic stress increase energy quenching, photorespiration, stomatal closure, and leaf temperature, while toning down photosynthesis and transpiration. Locally applied stress induces ES, ROS, retrograde signalling, cell death, and cellular light memory, then acclimation and defence responses in the local organs, whole plant, or even plant community (systemic acquired acclimation, systemic acquired resistance, network acquired acclimation). A simplified analogy can be found in animals where diseases vs. fitness and prolonged lifespan vs. faster aging, are dependent on mitochondrial ROS production and ES, and body temperature is regulated by sweating, temperature-dependent respiration, and gene regulation. In this review, we discuss the universal features of stress factors, ES, the cellular production of ROS molecules, ROS scavengers, hormones, and other regulators that coordinate life and death.

Phyllosphere bacterial communities in urban green areas throughout Europe relate to urban intensity.

The phyllosphere harbours a diverse and specific bacterial community, which influences plant health and ecosystem functioning. In this study, we investigated the impact of urban green areas connectivity and size on the composition and diversity of phyllosphere bacterial communities. Hereto, we evaluated the diversity and composition of phyllosphere bacterial communities of 233 Platanus x acerifolia and Acer pseudoplatanus trees in 77 urban green areas throughout 6 European cities. The community composition and diversity significantly differed between cities but only to a limited extent between tree species. We could show that urban intensity correlated significantly with the community composition of phyllosphere bacteria. In particular, a significant correlation was found between the relative abundances for 29 out of the 50 most abundant families and the urban intensity: the abundances of classic phyllosphere families, such as Acetobacteraceae, Planctomycetes, and Beijerinkiaceae, decreased with urban intensity (i.e. more abundant in areas with more green, lower air pollution, and lower temperature), while those related to human activities, such as Enterobacteriaceae and Bacillaceae, increased with urban intensity. The results of this study suggest that phyllosphere bacterial communities in European cities are associated with urban intensity and that effect is mediated by several combined stress factors.

The levels of oxidative stress in a combination of stress factors.

We studied the effect of the combined action of ionizing radiation and induced immobilization stress on the lipid peroxidation process and antioxidant protection of organs (mesenteric lymph nodes, spleen, adrenal glands, thymus, and liver) and immune cels - the blood lymphocytes. Results were obtained on the role of free-radical oxidation in combination with exposure to ionizing radiation and immobilization stress at an early stage in the experiment. Gamma radiation in the acute period resulted in significant changes in lipoperoxidation and antioxidant systems. The first period of immobilization stress was marked by the imbalance of LPO-AOS systems disturbance with an accumulation of toxic compounds in tissues which had affected their function. The combined sublethal gamma radiation and immobilization stress disturbed the functional activity of adaptive systems of the body in the early stage of adaptation syndrome. Furthermore, the results show the dominant role of ionizing radiation in it.

Effect of Drought and Low P on Yield and Nutritional Content in Common Bean

Common bean (Phaseolus vulgaris L.) production in the tropics typically occurs in rainfed systems on marginal lands where yields are low, primarily as a consequence of drought and low phosphorus (P) availability in soil. This study aimed to investigate the physiological and chemical responses of 12 bush bean genotypes for adaptation to individual and combined stress factors of drought and low P availability. Water stress and P deficiency, both individually and combined, decreased seed weight and aboveground biomass by ∼80%. Water deficit and P deficiency decreased photosynthesis and stomatal conductance during plant development. Maximum rates of carboxylation, electron transport, and triose phosphate utilization were superior for two common bean genotypes (SEF60 and NCB226) that are better adapted to combined stress conditions of water deficit and low P compared to the commercial check (DOR390). In response to water deficit treatment, carbon isotope fractionation in the leaf tissue decreased at all developmental stages. Within the soluble leaf fraction, combined water deficit and low P, led to significant changes in the concentration of key nutrients and amino acids, whereas no impact was detected in the seed. Our results suggest that common bean genotypes have a degree of resilience in yield development, expressed in traits such as pod harvest index, and conservation of nutritional content in the seed. Further exploration of the chemical and physiological traits identified here will enhance the resilience of common bean production systems in the tropics.

Synthesis of Secretory Proteins in Yarrowia lipolytica: Effect of Combined Stress Factors and Metabolic Load.

While overproduction of recombinant secretory proteins (rs-Prots) triggers multiple changes in the physiology of the producer cell, exposure to suboptimal growth conditions may further increase that biological response. The environmental conditions may modulate the efficiency of both the rs-Prot gene transcription and translation but also the polypeptide folding. Insights into responses elicited by different environmental stresses on the rs-Prots synthesis and host yeast physiology might contribute to a better understanding of fundamental biology processes, thus providing some clues to further optimise bioprocesses. Herein, a series of batch cultivations of Yarrowia lipolytica strains differentially metabolically burdened by the rs-Prots overproduction have been conducted. Combinations of different stress factors, namely pH (3/7) and oxygen availability (kLa 28/110 h−1), have been considered for their impact on cell growth and morphology, substrate consumption, metabolic activity, genes expression, and secretion of the rs-Prots. Amongst others, our data demonstrate that a highly metabolically burdened cell has a higher demand for the carbon source, although presenting a compromised cell growth. Moreover, the observed decrease in rs-Prot production under adverse environmental conditions rather results from the emergence of a less-producing cell subpopulation than from the decrease of the synthetic capacity of the whole cell population.

Systematic Long-Term Cycling of 18650 Batteries Beyond 80% Capacity

The true useful life of secondary Li-ion batteries is currently not well characterized. 80% of initial capacity, a decades old metric for vehicle applications, is a common endpoint in literature cycling studies and commercial cell specification sheets. As such, much is not known about cell performance beyond this metric. The 80% cutoff may not be applicable for non-vehicle applications, like grid energy storage, where there are different requirements for performance. Degradation data beyond the 80% capacity threshold is needed to make these evaluations.To address this, we have been conducting a multi-year study of both cycling and calendar aging of 18650 cells. During this study, LiFePO4/LFP, LiNixCoyAl1-x-yO2/NCA, and LiNixMnyCo1-x-yO2/NMC cells have been cycled at systematically varied temperature, state of charge (SOC) ranges, and cycling rates. Our group has previously reported on trends in cells as they were cycled to 80% capacity [1]. In this study it was generally found that SOC range impacted the capacity fade rates most significantly. Here, we present an update on performance of cells cycled beyond 80% capacity. We aim to identify so called knee points, and determine what conditions extend useful life of the cells.Results so far suggest that SOC range continues to be the largest factor in capacity fade rate. Also, combination of stress factors (high SOC with low temperature) causes rapid capacity fade beyond what would be expected by simple addition of degradation rates from the individual stress factors. Some cells do not appear to have a knee point as they have been in rapid degradation modes from the start of cycling. Cells that do display a knee have onset points that vary by chemistry and conditions of cycling. This study represents the broadest public report of post 80% capacity cycling across multiple chemistries. It will inform cell lifetime prediction and allow for better utilization of battery systems.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2021-5032 A

Dissection of Root Transcriptional Responses to Low pH, Aluminum Toxicity and Iron Excess Under Pi-Limiting Conditions in Arabidopsis Wild-Type and stop1 Seedlings.

Acidic soils constrain plant growth and development in natural and agricultural ecosystems because of the combination of multiple stress factors including high levels of Fe3+, toxic levels of Al3+, low phosphate (Pi) availability and proton rhizotoxicity. The transcription factor SENSITIVE TO PROTON RHIZOTOXICITY (STOP1) has been reported to underlie root adaptation to low pH, Al3+ toxicity and low Pi availability by activating the expression of genes involved in organic acid exudation, regulation of pH homeostasis, Al3+ detoxification and root architecture remodeling in Arabidopsis thaliana. However, the mechanisms by which STOP1 integrates these environmental signals to trigger adaptive responses to variable conditions in acidic soils remain to be unraveled. It is unknown whether STOP1 activates the expression of a single set of genes that enables root adaptation to acidic soils or multiple gene sets depending on the combination of different types of stress present in acidic soils. Previous transcriptomic studies of stop1 mutants and wild-type plants analyzed the effect of individual types of stress prevalent in acidic soils. An integrative study of the transcriptional regulation pathways that are activated by STOP1 under the combination of major stresses common in acidic soils is lacking. Using RNA-seq, we performed a transcriptional dissection of wild-type and stop1 root responses, individually or in combination, to toxic levels of Al3+, low Pi availability, low pH and Fe excess. We show that the level of STOP1 is post-transcriptionally and coordinately upregulated in the roots of seedlings exposed to single or combined stress factors. The accumulation of STOP1 correlates with the transcriptional activation of stress-specific and common gene sets that are activated in the roots of wild-type seedlings but not in stop1. Our data indicate that perception of low Pi availability, low pH, Fe excess and Al toxicity converges at two levels via STOP1 signaling: post-translationally through the regulation of STOP1 turnover, and transcriptionally, via the activation of STOP1-dependent gene expression that enables the root to better adapt to abiotic stress factors present in acidic soils.

Photocatalyst (TiO2) as an enhancer: an attempt to enhance the production of carotenoids and lipids with the combined oxidative stresses in Coelastrella sp. M60

Microalgae are important biological resources which attract the researchers for the production of valuable products like bio-energy and value-added products. In this study, enhanced accumulation of carotenoids and lipids was obtained from Coelastrella sp. M60 which was grown at 40 °C, along with different stress conditions (nitrogen starvation, salinity and TiO2). The results clearly indicate that osmotic stress and nitrogen starvation along with high temperature had induced the yield of zeaxanthin (13.15 mg/g DCW) and the lipid content (39.51 ± 5.13%). Further, it was also observed that TiO2 combined with other stresses had induced the increased accumulation of astaxanthin and zeaxanthin up to 1.16 and 0.51 fold on the 10th day of cultivation. On the contrary, TiO2, along with other stress conditions had influenced the biomass production up to 1.16 fold than the control, but no detectable increase in lipid content was observed. Thus, for the first time it is reported that by employing combined stress factors such as high temperature, nitrogen starvation and 3% salinity had resulted in significant improvement in zeaxanthin production in the foresaid microalgae. Further, it was also noticed that the Coelastrella sp. M60 had accumulated the carotenoids and lipids under TiO2 along with other oxidative stress conditions within the short duration.