Neslihan Turgut-Kara

Selenium Metabolism in Plants: Molecular Approaches

Selenium (Se) is placed in Group VIA of the Periodic Table. Its chemistry is similar to sulfur (S). Practically all small organic selenium compounds are isologues of corresponding sulfur compounds. With a few exceptions, they are also isologues of sulfur amino acids or derivatives thereof. Selenium plays an indispensable role for humans, animals and microorganisms. It is beneficial for the metabolism at lower concentrations, whereas at higher concentrations it becomes toxic. In other words, the range between deficiency and toxicity is very narrow. Short-term consumption of high levels of Se by human and animals may cause nausea, vomiting, and diarrhea, whereas chronic consumption of high concentrations of Se compounds can result in a disease called selenosis (Goldhaber, 2003). Excess selenium in the environment can be the result of either natural geological processes or industrialization.

De Novo Transcriptome Assembly and Comparative Analysis Elucidate Complicated Mechanism Regulating Astragalus chrysochlorus Response to Selenium Stimuli

Astragalus species are medicinal plants that are used in the world for years. Some Astragalus species are known for selenium accumulation and tolerance and one of them is Astragalus chrysochlorus, a secondary selenium accumulator. In this study, we employed Illumina deep sequencing technology for the first time to de novo assemble A. chrysochlorus transcriptome and identify the differentially expressed genes after selenate treatment. Totally, 59,656 unigenes were annotated with different databases and 53,960 unigenes were detected in NR database. Transcriptome in A. chrysochlorus is closer to Glycine max than other plant species with 43,1 percentage of similarity. Annotated unigenes were also used for gene ontology enrichment and pathway enrichment analysis. The most significant genes and pathways were ABC transporters, plant pathogen interaction, biosynthesis of secondary metabolites and carbohydrate metabolism. Our results will help to enlighten the selenium accumulation and tolerance mechanisms, respectively in plants.

Detection of genetically modified organisms in soy products sold in Turkish market

PCR-based technique for GMO detection is the most reliable choice because of its high sensitivity and specificity. As a candidate of the European union, Turkey must comply with the rules for launching into the market, traceability, and labeling of GMOs as established by Eu legislation. Therefore, the objective of this study is to assess soybean products in the Turkish market to verify compliance with legislation using qualitative Polymerase Chain Reaction (PCR) assay to detect the presence of GM soybean and to quantify its amount of GM soybean in the samples tested positive using real-time PCR. DNA extracted by the modified CTAB method was properly used for PCR amplification of food materials. The amplification of a 118 bp DNA fragment of the lectin gene from soybean by PCR was successfully achieved in all samples. The GMO screening was based on the detection of 35S promoter and NOS terminator sequences. The GM positive samples were subjected to detection of Roundup Ready TM soybean (RR) using quantitative real-time PCR. It was found that 100% of the tested food samples contained less than 0.1 per cent of EPSPS gene.

Selenium induced selenocysteine methyltransferase gene expression and antioxidant enzyme activities in Astragalus chrysochlorus

Abstract Astragalus sp. are used in folk medicine because of their biological activities and are known for the ability to accumulate high levels of selenium (Se). The purpose of this study was to explore gene expression of selenocysteine methyltransferase (SMT), responsible for forming MeSeCys, and activities of ascorbate peroxidase (APX), peroxidase (POX), catalase (CAT) and glutathione reductase (GR) enzymes in callus tissues of Astragalus chrysochlorus growing in different Se-containing media. Quantitative real-time polymerase chain reaction assay was done for quantification of SMT gene transcript and it was normalized to actin gene. It was found that transcript level of callus tissues grown at 5.2 μM and 26.4 μM Se-enriched media was lower than that of the control callus. In contrast, a high level of Se (132.3 μM) in the medium caused an approximately 4.26 times higher level of SMT transcript in callus than the control. APX, POX, CAT and GR enzymes were all effected by different Se concentrations. While POX and APX activities were higher then control, CAT and GR activities decreased. These results show that an increase of SMT gene expression led to a rise in APX and POX, but a suppression of CAT and GR enzymes activities in Astragalus chrysochlorus. This suggests that Se could be involved in the antioxidant metabolism in Astragalus chrysochlorus.

Epigenetics and Applications in Plants

As seen in other eukaryotic cells, DNA is coiled tightly around the histone proteins in plant cells. Pathways that end with cytosine DNA methylation, posttranslational histone modifications, and RNA interference (RNAi) contribute importantly to the regulation of chromatin structure and hence affect many cellular events. High-throughput sequencing analysis on a genome-wide scale brings new understanding about plant genomes and the functions of epigenetic pathways. Although epigenetics has become an important research field in the post-genomic era and even though we can use many model organisms whose epigenomes have been sequenced for many years, we still far from having full knowledge about the regulation of gene expression. This chapter mainly focuses on the characteristics of the field of epigenetics and its applications in plants.