Füsun Eyidoğan

Antioxidant responses of shoots and roots of lentil to NaCl-salinity stress

The effect of salt stress (100 mM and 200 mM NaCl) on antioxidant responses in shoots and roots of 14-day-old lentil (Lens culinaris M.) seedlings was investigated. Salt stress caused a significant decrease in length, wet-dry weight and an increase in proline content of both shoot and root tissues. In leaf tissues, high salinity treatment resulted in a 4.4 fold increase in H2O2 content which was accompanied by a significant level of lipid peroxidation and an increase in electrolyte leakage. Root tissues were less affected with respect to these parameters. Leaf tissue extracts exhibited four activity bands, of which two were identified as Cu/Zn-SOD and others as Fe-SOD and Mn-SOD. Fe-SOD activity was missing in root extracts. In both tissues Cu/Zn-SOD activity comprised 70–75% of total SOD activity. Salt stress did not cause a significant increase in total SOD activity of leaf tissues but a significant enhancement (88%) was observed in roots mainly due to an enhancement in Cu/ZnSOD isoforms. Compared to leaf tissues a significantly higher constitutive ascorbate peroxidase (APX) and glutathion reductase (GR) activity was observed in root tissues. Upon salt stress no significant change in the activity of APX, catalase (CAT) and GR was observed in root tissues but a higher APX activity was present when compared to leaf tissues. On the other hand, in leaf tissues, with the exception of CAT, salt stress caused significant enhancement in the activity of other antioxidant enzymes. These results suggested that, root tissues of lentil are protected better from NaCl stress induced oxidative damage due to enhanced total SOD activity together with a higher level of APX activity under salinity stress. To our knowledge this is the first report describing antioxidant enzyme activities in lentil.

Aptamer-Gated Nanoparticles for Smart Drug Delivery

Aptamers are functional nucleic acid sequences which can bind specific targets. An artificial combinatorial methodology can identify aptamer sequences for any target molecule, from ions to whole cells. Drug delivery systems seek to increase efficacy and reduce side-effects by concentrating the therapeutic agents at specific disease sites in the body. This is generally achieved by specific targeting of inactivated drug molecules. Aptamers which can bind to various cancer cell types selectively and with high affinity have been exploited in a variety of drug delivery systems for therapeutic purposes. Recent progress in selection of cell-specific aptamers has provided new opportunities in targeted drug delivery. Especially functionalization of nanoparticles with such aptamers has drawn major attention in the biosensor and biomedical areas. Moreover, nucleic acids are recognized as an attractive building materials in nanomachines because of their unique molecular recognition properties and structural features. A active controlled delivery of drugs once targeted to a disease site is a major research challenge. Stimuli-responsive gating is one way of achieving controlled release of nanoparticle cargoes. Recent reports incorporate the structural properties of aptamers in controlled release systems of drug delivering nanoparticles. In this review, the strategies for using functional nucleic acids in creating smart drug delivery devices will be explained. The main focus will be on aptamer-incorporated nanoparticle systems for drug delivery purposes in order to assess the future potential of aptamers in the therapeutic area. Special emphasis will be given to the very recent progress in controlled drug release based on molecular gating achieved with aptamers.

Cu/Zn superoxide dismutase activity and respective gene expression during cold acclimation and freezing stress in barley cultivars

The transcript levels and activities of the superoxide dismutase isoenzyme (Cu/ZnSOD) were assessed in winter (Tarm-92) and spring (Zafer-160) barley cultivars during cold acclimation, freezing stress and after rewarming. Leaf Cu/ZnSOD activity and Cu/ZnSOD expression level were not significantly changed during cold acclimation. The Cu/ZnSOD expression increased evidently at mild freezing stress (−3 °C; F1), while Cu/ZnSOD1 activity did not show any response and Cu/ZnSOD2 activity decreased continuously during F1 and F2 (−7 °C) in Tarm-92. On the other hand, root Cu/ZnSOD2 activity was in accordance with Cu/ZnSOD expression in Zafer-160 after F2 treatment. Rewarming periods did not cause any significant changes in the Cu/ZnSOD activity and expression of Cu/ZnSOD in both cultivars when compared to freezing stresses. These results showed that freezing stress can regulate differently Cu/ZnSOD transcription and enzyme activity.

DNA aptamer-based colorimetric detection platform for Salmonella Enteritidis

Food safety is a major issue to protect public health and a key challenge is to find detection methods for identification of hazards in food. Food borne infections affects millions of people each year and among pathogens, Salmonella Enteritidis is most widely found bacteria causing food borne diseases. Therefore, simple, rapid, and specific detection methods are needed for food safety. In this study, we demonstrated the selection of DNA aptamers with high affinity and specificity against S. Enteritidis via Cell Systematic Evolution of Ligands by Exponential Enrichment (Cell-SELEX) and development of sandwich type aptamer-based colorimetric platforms for its detection. Two highly specific aptamers, crn-1 and crn-2, were developed through 12 rounds of selection with Kd of 0.971µM and 0.309µM, respectively. Both aptamers were used to construct sandwich type capillary detection platforms. With the detection limit of 103 CFU/mL, crn-1 and crn-2 based platforms detected target bacteria specifically based on color change. This platform is also suitable for detection of S. Enteritidis in complex food matrix. Thus, this is the first to demonstrate use of Salmonella aptamers for development of the colorimetric aptamer-based detection platform in its identification and detection with naked eye in point-of-care.

Signal Transduction of Phytohormones Under Abiotic Stresses

Growth and productivity of higher plants are adversely affected by various environmental stresses which are of two main types, biotic and abiotic, depending on the source of stress. Broad range of abiotic stresses includes osmotic stress caused by drought, salinity, high or low temperatures, freezing, or flooding, as well as ionic, nutrient, or metal stresses, and others caused by mechanical factors, light, or radiation. Plants contrary to animals cannot escape from these environmental constraints, and over the course of evolution, they have developed some physiological, biochemical, or molecular mechanisms to overcome effects of stress. Phytohormones such as auxin, cytokinin, abscisic acid, jasmonic acid, ethylene, salicylic acid, gibberellic acid, and few others, besides their functions during germination, growth, development, and flowering, play key roles and coordinate various signal transduction pathways in plants during responses to environmental stresses. Complex networks of gene regulation by these phytohormones under abiotic stresses involve various cis- or trans-acting elements. Some of the transcription factors regulated by phytohormones include ARF, AREB/ABF, DREB, MYC/MYB, NAC, and others. Changes in gene expression, protein synthesis, modification, or degradation initiated by or coupled to these transcription factors and their corresponding cis-acting elements are briefly summarized in this work. Moreover, crosstalk between signal transduction pathways involving phytohormones is explained in regard to transcriptional or translational regulation under abiotic stresses.

Superoxide dismutase activity in salt stressed wheat seedlings

We investigated the effect of salt stress on enzymatic activity of superoxide dismutase (SOD) isozymes in shoot and root tissues of salt tolerant and sensitive wheat (Triticum aestivum L. and Triticum durum Defs.) cultivars. Ten day old seedlings were subjected to 0.7 M NaCl stress for 3 and 5 days. Seedlings treated in the same manner without salt stress served as controls. Activity of SOD isozymes in root and shoot extracts was determined by activity staining of native polyacrylamide gels. In both shoot and root extracts of examined cultivars two isozymes of SOD, namely MnSOD and Cu/ZnSOD were identified. Cu/ZnSOD activity comprised 90 % of total SOD activity in both root and shoot tissues. Salt stress caused 1–1.5 fold increase in MnSOD activity of shoots in tolerant cultivars when compared with non-stressed controls. Under stress conditions, compared to controls all cultivars exhibited reduced MnSOD activity in root tissues. Cu/ZnSOD activity, on the other hand, was remarkably enhanced (3–4 fold) in root extracts of the tolerant cultivars, whereas it was reduced in the sensitive ones.

Evaluation of photosynthetic performance of wheat cultivars exposed to boron toxicity by the JIP fluorescence test

The changes in growth and photosynthetic performance of two wheat (Triticum aestivum L.) cultivars (Bolal-2973 and Atay-85) differing in their sensitivity to boron (B) toxicity were investigated under toxic B conditions. Eight-day old seedlings were exposed to highly toxic B concentrations (5, 7.5, and 10 mM H3BO3) for 5 and 9 days. Fast chlorophyll a fluorescence kinetics was determined and analysed using JIP test. Growth parameters, tissue B contents, and membrane damage were measured at two stress durations. The photochemical performance of PSII was hindered more in the sensitive cultivar (Atay-85) than that of the tolerant one (Bolal-2973) under B toxicity. The increase in the B concentration and stress duration caused membrane leakage in both cultivars. However, higher membrane damage was observed in Atay-85 compared to Bolal-2973. Additionally, significant reduction of growth parameters was observed in both cultivars at toxic B concentrations. The accumulation of B was higher in shoots than in roots of both cultivars. Nevertheless, Atay-85 translocated more B from roots to leaves compared to Bolal-2973. The advantages of certain JIP test parameters were demonstrated for evaluation of PSII activity in plants exposed to B stress. Evaluation of photosynthetic performance by JIP test as well as assessment of growth and tissue B content might be used to determine the effects of B toxicity in wheat. The results indicated lesser sensitivity to B toxicity in Bolal-2973 compared to Atay-85.

Development of a paper‐type tyrosinase biosensor for detection of phenolic compounds

A low‐cost, portable, and disposable paper‐type tyrosinase biosensor was developed for determination of phenolic compounds, using a paper‐strip absorption method. Tyrosinase and a chromophore (3‐methyl‐2‐benzothiazolinone hydrazone) were immobilized on paper strips to manufacture the biosensor, which was tested on a nontoxic substrate (l‐dopamine). The biosensor was responsive to phenolic compounds such as 4‐chlorophenol, catechol, m‐cresol, and p‐cresol. The sensor showed stability for 70 days. The developed biosensor can be used for remote on‐site qualitative monitoring of phenolic compounds in wastewater samples.

Physiological, Biochemical, and Transcriptomic Responses to Boron Toxicity in Leaf and Root Tissues of Contrasting Wheat Cultivars

In this study, we examined physiological, biochemical, and transcriptomic responses to toxic boron (B) treatment in leaves and roots of two wheat cultivars in order to gain better insight into B response or tolerance mechanisms. Delayed development and reduced vigor caused by high B were not observed in leaves and roots of both cultivars. Length, wet weight, and dry weight were not markedly changed under B toxicity. In leaves, when compared to control, 995 and 892 genes were significantly expressed at least twofold under B toxicity in Atay and Bolal, respectively. In roots, expressions of 1248 and 957 genes were responsive to B toxicity in Atay and Bolal, respectively. In leaf and root tissues, B toxicity induced more genes related to protein degradation in Atay than those in Bolal. These differences in transcriptome were attributed to higher B accumulation in the sensitive cultivar which required high level of metabolic adjustment. B toxicity stress did not cause any significant change in photosynthetic activity and contents of proline and glycine betaine in both cultivars. Coordinately, we did not find any differentially expressed genes required for proline and glycine betaine metabolisms. Genes related to hormone signaling, kinases, transcription factors such as WRKY and MYB, and key enzymes in reactive oxygen species (ROS) scavenging mechanisms were differentially affected by B toxicity in both cultivars. Among commonly regulated genes in Atay and Bolal, glutathione S-transferase (GST) and NIP4;1 (nodulin-26-like intrinsic proteins) genes stand out as prominent actors in B stress response.

Functional Role of Nitric Oxide Under Abiotic Stress Conditions

Nitric oxide (NO), a free radical in living organisms, is considered a phytohormone and a key signalling molecule functioning in various physiological processes of plants. These physiological processes include germination, growth, senescence, and photosynthesis as well as response mechanisms to specific environmental stresses. Plants under abiotic stress conditions experience oxidative and nitrosative stress ; the latter mainly elicited by regulation of NO production. Nitrosative stress describes the molecular or cellular damage promoted by imbalance in NO homeostasis and other reactive nitrogen species . Additionally, depending on its concentration and location in plant cells or tissues, NO might function as an antioxidant and scavenge some other reactive intermediates. Direct or indirect involvement of NO in response mechanisms under water stress, drought, salinity, heavy metal stress, high or low temperature extremities, and ultraviolet radiation has been reported. In this work, the recent findings and current knowledge on the function of NO in plants under abiotic stress conditions are reviewed briefly.