High-throughput transcriptome analysis of barley (Hordeum vulgare) exposed to excessive boron.

Boron (B) is an essential micronutrient for optimum plant growth. However, above certain threshold B is toxic and causes yield loss in agricultural lands. While a number of studies were conducted to understand B tolerance mechanism, a transcriptome-wide approach for B tolerant barley is performed here for the first time. A high-throughput RNA-Seq (cDNA) sequencing technology (Illumina) was used with barley (Hordeum vulgare), yielding 208 million clean reads. In total, 256,874 unigenes were generated and assigned to known peptide databases: Gene Ontology (GO) (99,043), Swiss-Prot (38,266), Clusters of Orthologous Groups (COG) (26,250), and the Kyoto Encyclopedia of Genes and Genomes (KEGG) (36,860), as determined by BLASTx search. According to the digital gene expression (DGE) analyses, 16% and 17% of the transcripts were found to be differentially regulated in root and leaf tissues, respectively. Most of them were involved in cell wall, stress response, membrane, protein kinase and transporter mechanisms. Some of the genes detected as highly expressed in root tissue are phospholipases, predicted divalent heavy-metal cation transporters, formin-like proteins and calmodulin/Ca(2+)-binding proteins. In addition, chitin-binding lectin precursor, ubiquitin carboxyl-terminal hydrolase, and serine/threonine-protein kinase AFC2 genes were indicated to be highly regulated in leaf tissue upon excess B treatment. Some pathways, such as the Ca(2+)-calmodulin system, are activated in response to B toxicity. The differential regulation of 10 transcripts was confirmed by qRT-PCR, revealing the tissue-specific responses against B toxicity and their putative function in B-tolerance mechanisms.

Randomly amplified polymorphic-DNA analysis for detecting genotoxic effects of Boron on maize (Zea mays L.).

This study was carried out to investigate the genotoxic effect of boron (B) on maize using randomly amplified polymorphic DNA (RAPD) method. Experimental design was conducted under 0, 5, 10, 25, 50, 100, 125, and 150 ppm B exposures, and physiological changes have revealed a sharp decrease in root growth rates from 28% to 85%, starting from 25 ppm to 150 ppm, respectively. RAPD-polymerase chain reaction (PCR) analysis shows that DNA alterations are clearly observed from beginning to 100 ppm. B-induced inhibition in root growth had a positive correlation with DNA alterations. Total soluble protein, root and stem lengths, and B content analysis in root and leaves encourage these results as a consequence. These preliminary findings reveal that B causes chromosomal aberration and genotoxic effects on maize. Meanwhile, usage of RAPD-PCR technique is a suitable biomarker to detect genotoxic effect of B on maize and other crops for the future.

Genotoxic effects of catmint (Nepeta meyeri Benth.) essential oils on some weed and crop plants.

This study investigates the genotoxicity of the essential oils extracted from the aerial parts of catmint (Nepeta meyeri Benth.) against two weeds (Bromus danthoniae and Lactuca serriola) and two crop plants (Brassica napus and Zea mays). The essential oils of N. meyeri analyzed by gas chromatography-mass spectrometry contained 14 compounds, with 4aα, 7α, 7aß-nepetalactone (83.4%), 4aα, 7α, and 7aα-nepetalactone (8.83%) as the major components. The oils were diluted (25, 50, 100, and 150 ppm) and the solutions were applied to seeds or leaves of these plants. The study compared the germination percentage and random amplified polymorphic DNA (RAPD) results with the control group. The results showed that the oils had a strong inhibitory activity and caused a change in RAPD profiles in terms of variation in band intensity, loss of bands, and appearance of new bands compared with the control group. The results suggested that RAPD analysis could be applied as a suitable biomarker assay for the detection of genotoxic effects of plant allelochemicals. This study indicates the genotoxical potential of N. meyeri essential oils on weed and crop plants.

Ecophysiological responses of some maquis (Ceratonia siliqua L., Olea oleaster Hoffm. & Link, Pistacia lentiscus and Quercus coccifera L.) plant species to drought in the east Mediterranean ecosystem.

The objective was to examine the adaptation strategies of four maquis species to drought prone environments; typical of the east Mediterranean area in degraded and healthy sites in Turkey. A comparison made between sites for Pistacia lentiscus and Quercus coccifera shows higher net daily photosynthesis in the degraded site, when compared with the healthy site; but Ceratonia siliqua and Olea oleaster exhibited no difference in their photosynthetic activity in environmentally contrasting conditions. The pattern of daily transpiration shows higher values in the degraded site in the case of P. lentiscus and Q. coccifera, while no site effect was observed for C. siliqua and O. oleaster. In the case of Q. coccifera, a behavior similar to C. siliqua was observed. A comparison made between C. siliqua and O. oleaster to observe seasonal differences in daily patterns of net photosynthesis and transpiration reveals that Q. coccifera had the highest water use efficiency (slope= 2.88; r2 = 0.61), followed by C. siliqua (slope = 2.74; r2 = 0.7), P. lentiscus (slope = 2.56; r2 = 0.52) and O. oleaster (slope = 2.40; r2 = 0.78). Olea oleaster and P. lentiscus performed as a drought tolerant species, being more resistant to aridity and thus indicative of the degradation state of the site. Ceratonia siliqua and Q. coccifera were found avoiding drought by adopting first a water-spending strategy, and then a water-saving strategy.

Assessment of genotoxic effects of boron on wheat (Triticum aestivum L.) and bean (Phaseolus vulgaris L.) by using RAPD analysis.

In boron-rich soils of Turkey, boron tolerant wheat (Triticum aestivum L.) and sensitive bean (Phaseolus vulgaris L.) are most widely cultivated crops. In this study they have been studied to elucidate the probable genotoxic effects of boron by using RAPD analysis. During the study, root and stem lengths have been measured and inhibitory rates (%) of root growth have been found to be significant, starting from 10 (13%) and 5 ppm (19%) for wheat and bean, respectively, which is in strong correlation with the root DNA alterations; RAPD variations starting from 100 ppm for wheat and 25 ppm for bean. The preliminary findings encourage the use of these tools in investigation of genotoxic effects of boron on wheat, bean and the other crops.