Variations in BARE-1 insertion patterns in barley callus cultures

5-Aminolevulinic acid treatment mitigates pesticide stress in bean seedlings by regulating stress-related gene expression and retrotransposon movements

Overdoses of pesticides lead to a decrease in the yield and quality of plants, such as beans. The unconscious use of deltamethrin, one of the synthetic insecticides, increases the amount of reactive oxygen species (ROS) by causing oxidative stress in plants. In this case, plants tolerate stress by activating the antioxidant defense mechanism and many genes. 5-Aminolevulinic acid (ALA) improves tolerance to stress by acting exogenously in low doses. There are many gene families that are effective in the regulation of this mechanism. In addition, one of the response mechanisms at the molecular level against environmental stressors in plants is retrotransposon movement. In this study, the expression levels of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), and stress-associated protein (SAP) genes were determined by Q-PCR in deltamethrin (0.5 ppm) and various doses (20, 40, and 80 mg/l) of ALA-treated bean seedlings. In addition, one of the response mechanisms at the molecular level against environmental stressors in plants is retrotransposon movement. It was determined that deltamethrin increased the expression of SOD (1.8-fold), GPX (1.4-fold), CAT (2.7-fold), and SAP (2.5-fold) genes, while 20 and 40 mg/l ALA gradually increased the expression of these genes at levels close to control, but 80 mg/l ALA increased the expression of these genes almost to the same level as deltamethrin (2.1-fold, 1.4-fold, 2.6-fold, and 2.6-fold in SOD, GPX, CAT, and SAP genes, respectively). In addition, retrotransposon-microsatellite amplified polymorphism (REMAP) was performed to determine the polymorphism caused by retrotransposon movements. While deltamethrin treatment has caused a decrease in genomic template stability (GTS) (27%), ALA treatments have prevented this decline. At doses of 20, 40, and 80 mg/L of ALA treatments, the GTS ratios were determined to be 96.8%, 74.6%, and 58.7%, respectively. Collectively, these findings demonstrated that ALA has the utility of alleviating pesticide stress effects on beans.

Androgenic-Induced Transposable Elements Dependent Sequence Variation in Barley

A plant genome usually encompasses different families of transposable elements (TEs) that may constitute up to 85% of nuclear DNA. Under stressful conditions, some of them may activate, leading to sequence variation. In vitro plant regeneration may induce either phenotypic or genetic and epigenetic changes. While DNA methylation alternations might be related, i.e., to the Yang cycle problems, DNA pattern changes, especially DNA demethylation, may activate TEs that could result in point mutations in DNA sequence changes. Thus, TEs have the highest input into sequence variation (SV). A set of barley regenerants were derived via in vitro anther culture. High Performance Liquid Chromatography (RP-HPLC), used to study the global DNA methylation of donor plants and their regenerants, showed that the level of DNA methylation increased in regenerants by 1.45% compared to the donors. The Methyl-Sensitive Transposon Display (MSTD) based on methylation-sensitive Amplified Fragment Length Polymorphism (metAFLP) approach demonstrated that, depending on the selected elements belonging to the TEs family analyzed, varying levels of sequence variation were evaluated. DNA sequence contexts may have a different impact on SV generated by distinct mobile elements belonged to various TE families. Based on the presented study, some of the selected mobile elements contribute differently to TE-related SV. The surrounding context of the TEs DNA sequence is possibly important here, and the study explained some part of SV related to those contexts.

BAGY2 retrotransposon analyses in barley calli cultures and regenerated plantlets

The stability of aging barley calli and regenerated plantlets from those calli was investigated by the BAGY2 retrotransposon-specific IRAP technique. Mature embryos of barley (Hordeum vulgare cv. Golden Promise) were cultured in Murashige and Skoog medium supplemented with 4 mg/L dicamba and maintained on the same medium for 45 and 90 days. Two IRAP-based primers were used, and the levels of variation of DNA isolated from 45- and 90-day-old calli and regenerated plantlets were found to be increased 0-21%, depending on the mature embryo material and the age of the callus. It has been observed that culture conditions cause genetic variations and evident BAGY2 retrotransposon alterations. Internal domains of BAGY2 were also analyzed by qPCR, and copy numbers were found to be increased. These findings are expected to contribute to understanding of how retrotransposons affect features like tissue culture (especially callus tissue) formation and genetic engineering studies.

Human endogenous retrovirus-H insertion screening

Endogenous retroviruses (ERVs) and ERV-like sequences comprise 8% of the human genome. We aimed to analyze genome integration polymorphisms of human endogenous retrovirus (HERV)-H by the inter-retrotransposon amplified polymorphism (IRAP) technique using the sequences of LTR7A (450 bp), LTR7B (445 bp) and LTR7C (471 bp). Blood samples from 20 individuals (10 females and 10 males) of diverse ethnic origins were used for the determination of integration variations at the genomic level. Isolated genomic DNA was screened using 3 pairs of primers corresponding to LTR regions of the HERV-H gene. We observed insertion polymorphism patterns between 0-87% in all subjects. The findings obtained contribute to our understanding of the effects of HERV-H on variations within the human genome.

Effects of epirubicin on barley seedlings

Epirubicin (EPI) is one of the anthracycline antibiotics, which is used in cancer chemotherapy. It inhibits DNA and RNA synthesis and causes cell death by DNA cleavage and production of free radicals. In this study, phytotoxicity of EPI was investigated on root and shoot growth, antioxidant enzymes and retrotransposons’ movements in 10- and 20-day-old barley seedlings. Mature embryos of barley were germinated on Murashige and Skoog medium supplemented with 250 and 500 μg/ml EPI. Our results showed that EPI treatment significantly inhibited shoot and root growth when compared with control group. Treatment with 250 and 500 μg/ml of EPI reduced shoot length in the 10-day-old plants by approximately 1.5- and 2-fold, respectively; the same treatments reduced total root length by 2- and 4-folds, respectively. However, the shoot and root lengths of 20-day-old plants were observed to be more affected by EPI-treatment. A 500-μg/ml concentration decreased total protein levels and peroxidase (EC 1.11.1.11) activity and increased superoxide dismutase (EC 1.15.1.1) and catalase (EC 1.11.1.6) activities. To investigate the effect of EPI on the movements of BARE-1, SUKKULA and BAGY2 retrotransposons, inter-retrotransposon amplified polymorphism technique was performed. While some polymorphic polymerase chain reaction bands were observed for BARE-1, no polymorphism was identified in SUKKULA and BAGY2 movements. To our knowledge, this is the first report showing phytotoxic effects of EPI on plant germination and retrotransposons’ movements.

Recent progress in the understanding of tissue culture-induced genome level changes in plants and potential applications

In vitro cell and tissue-based systems have tremendous potential in fundamental research and for commercial applications such as clonal propagation, genetic engineering and production of valuable metabolites. Since the invention of plant cell and tissue culture techniques more than half a century ago, scientists have been trying to understand the morphological, physiological, biochemical and molecular changes associated with tissue culture responses. Establishment of de novo developmental cell fate in vitro is governed by factors such as genetic make-up, stress and plant growth regulators. In vitro culture is believed to destabilize the genetic and epigenetic program of intact plant tissue and can lead to chromosomal and DNA sequence variations, methylation changes, transposon activation, and generation of somaclonal variants. In this review, we discuss the current status of understanding the genomic and epigenomic changes that take place under in vitro conditions. It is hoped that a precise and comprehensive knowledge of the molecular basis of these variations and acquisition of developmental cell fate would help to devise strategies to improve the totipotency and embryogenic capability in recalcitrant species and genotypes, and to address bottlenecks associated with clonal propagation.