Strategies of Molecular Signal Integration for Optimized Plant Acclimation to Stress Combinations.

Plant growth and survival in their natural environment require versatile mitigation of diverse threats. The task is especially challenging due to the largely unpredictable interaction of countless abiotic and biotic factors. To resist an unfavorable environment, plants have evolved diverse sensing, signaling, and adaptive molecular mechanisms. Recent stress studies have identified molecular elements like secondary messengers (ROS, Ca2+, etc.), hormones (ABA, JA, etc.), and signaling proteins (SnRK, MAPK, etc.). However, major gaps remain in understanding the interaction between these pathways, and in particular under conditions of stress combinations. Here, we highlight the challenge of defining "stress" in such complex natural scenarios. Therefore, defining stress hallmarks for different combinations is crucial. We discuss three examples of robust and dynamic plant acclimation systems, outlining specific plant responses to complex stress overlaps. (a) The high plasticity of root system architecture is a decisive feature in sustainable crop development in times of global climate change. (b) Similarly, broad sensory abilities and apparent control of cellular metabolism under adverse conditions through retrograde signaling make chloroplasts an ideal hub. Functional specificity of the chloroplast-associated molecular patterns (ChAMPs) under combined stresses needs further focus. (c) The molecular integration of several hormonal signaling pathways, which bring together all cellular information to initiate the adaptive changes, needs resolving.

Timeline of critically ill 2019 SARS-CoV-2 cases after onset of illness: Intensive care data from Turkey.

Introduction: This study aimed to evaluate the epidemiological, clinical, laboratory characteristics and treatment and clinical outcomes of severe COVID19 cases from a 3rd degree intensive care unit in Turkey. Materials and Methods: The study was conducted in a level three, 16-bed COVID intensive care unit. The investigation was planned as a retrospective and observational study. Patients who were admitted with COVID-19 pneumonia and respiratory failure in the intensive care unit between March 2020 and March 2021 and followed up due to critical illness were evaluated. Result: A total of 213 patients that were admitted to the intensive care unit with the diagnosis of COVID-19 pneumonia were included in the study. Median age of the patients was 66 (IQR 56.5-74) years, and 134 (62.9%) were males. One hundred and sixty-six (77.9%) of the patients had at least one comorbidity. Patients were followed up mainly with invasive mechanical ventilation [104 (48.8%)] and high flow nasal cannula [67 (31.5%)]. Median number of days was 7 (IQR 4-10) and included the first symptom onset to intensive care admission. The time to intubation was 9 (IQR 4-15) days, and the median day to intensive care discharge was 16 (IQR 11-23). After the symptoms started, first tocilizumab 9 (IQR 5-11) and pulse steroid treatment 8 (IQR 3-11) were found to be close to each other. In total, 95 (44.6%) of the 213 patients died. Conclusions: SARS-CoV-2 associated viral disease can progress after simple symptoms to hospital admission in a median of four days and to intensive care admission requiring intubation in a median of nine days. We believe that a better understanding of the clinical course of COVID-19 and its change between centers can be revealed through sharing information from different countries and centers.

Exogenous ascorbic acid improves defence responses of sunflower (Helianthus annuus) exposed to multiple stresses.

Ascorbic acid is an important antioxidant that plays role both on growth and development and also stress response of the plant. The purpose of this study was to determine the effect of ascorbate on physiological and biochemical changes of sunflower that was exposed to multiple stresses. Chlorophyll and carotenoid contents decreased and glutathione, ascorbate and malondialdehyde contents as well as antioxidant enzyme activities increased for sunflower plant that was exposed to 50 mM NaCl and pendimethalin at different concentrations. These changes were found to be more significant in groups simultaneously exposed to both stress factors. While malondialdehyde content decreased, chlorophyll, carotenoid, ascorbate, glutathione contents and antioxidant enzyme activities increased in plants treated exogenously with ascorbate, compared to the untreated samples. According to the findings of our study; compared to individual stress, the effect of stress is more pronounced in sunflower exposed to multiple stresses, and treatment with exogenous ascorbate reduces the negative effects of stress.

Exogenous jasmonic acid induces stress tolerance in tobacco (Nicotiana tabacum) exposed to imazapic.

Jasmonic acid (JA) is one of the important phytohormones, regulating the stress responses as well as plant growth and development. The aim of this study is to determine the effects of exogenous JA application on stress responses of tobacco plant exposed to imazapic. In this study, phytotoxic responses resulting from both imazapic and imazapic combined with JA treatment are investigated comparatively for tobacco plants. For plants treated with imazapic at different concentrations (0.030, 0.060 and 0.120mM), antioxidant enzyme activities (catalase, ascorbate peroxidase, glutathione S-transferase and glutathione reductase), carotenoids, glutathione and malondialdehyte (MDA) contents, jasmonic acid, abscisic acid and indole-3-acetic acid levels as well as herbicide residue amounts on leaves increased in general compared to the control group. In the plants treated with 45µM jasmonic acid, pigment content, antioxidant activity and phytohormone level increased whereas MDA content and the amount of herbicidal residue decreased compared to the non-treated plants. Our findings show that imazapic treatment induces some phytotoxic responses on tobacco leaves and that exogenous jasmonic acid treatment alleviates the negative effects of herbicide treatment by regulating these responses.

The physiological and biochemical effects of salicylic acid on sunflowers (Helianthus annuus) exposed to flurochloridone.

In this study, we comparatively evaluated the effects of the flurochloridone as well as flurochloridone and exogenously applied salicylic acid (SA) on Helianthus annuus L. to find out herbicide-induced toxicity reducing influence of SA. We examined and compared the physiological and biochemical effects of different concentrations of flurochloridone (11, 32 and 72 mM) in both the SA pre-treated and non-treated plants. The plants treated with flurochloridone exhibited reduced total chlorophyll, carotenoid, and relative water content compared to the control group, whereas the plants that were pre-treated with SA exhibited relatively higher values for the same physiological parameters. In the SA non-treated plants, the superoxide dismutase, glutathione reductase and glutathione S-transferase activities were increased in the treatment groups compared to the control group. In the treatment groups, these enzyme activities were decreased in the SA-pre-treated plants compared to the non-treated plants. Ascorbate peroxidase and catalase activities decreased in the flurochloridone-treated plants compared to the control plants. The ascorbate peroxidase activity increased in the control groups but decreased in the treatment groups in the SA pre-treated plants compared to the non-treated plants. However, SA treatment decreased the activity of catalase in the control and treatment groups compared to the plants that were not treated with SA. Flurochloridone treatment increased the malondialdehyde content in the treated groups compared to the control groups, whereas SA-pretreatment decreased malondialdehyde content compared to plants that were not treated with SA. Flurochloridone treatment increased endogenous SA content compared to the control. Although the residual levels of herbicide in the plants increased proportionately with increasing herbicide concentrations, the SA-pre-treated plants exhibited reduced residual herbicide levels compared to the plants that were not treated with SA. These results indicate that the flurochloridone induces various physiological and biochemical responses in non-target plants and that treatment with exogenous SA can increase stress resistance by altering these responses.