Comparative transcriptome provides molecular insight into defense-associated mechanisms against spider mite in resistant and susceptible common bean cultivars.

Common bean (Phaseolus vulgaris L.) is a major source of proteins and one of the most important edible foods for more than three hundred million people in the world. The common bean plants are frequently attacked by spider mite (Tetranychus urticae Koch), leading to a significant decrease in plant growth and economic performance. The use of resistant cultivars and the identification of the genes involved in plant-mite resistance are practical solutions to this problem. Hence, a comprehensive study of the molecular interactions between resistant and susceptible common bean cultivars and spider mite can shed light into the understanding of mechanisms and biological pathways of resistance. In this study, one resistant (Naz) and one susceptible (Akhtar) cultivars were selected for a transcriptome comparison at different time points (0, 1 and 5 days) after spider mite feeding. The comparison of cultivars in different time points revealed several key genes, which showed a change increase in transcript abundance via spider mite infestation. These included genes involved in flavonoid biosynthesis process; a conserved MYB-bHLH-WD40 (MBW) regulatory complex; transcription factors (TFs) TT2, TT8, TCP, Cys2/His2-type and C2H2-type zinc finger proteins; the ethylene response factors (ERFs) ERF1 and ERF9; genes related to metabolism of auxin and jasmonic acid (JA); pathogenesis-related (PR) proteins and heat shock proteins.

cDNA-AFLP analysis of transcripts induced in chickpea plants by TiO2 nanoparticles during cold stress.

We evaluated the effect of TiO2 nanoparticles (NPs) on cold tolerance (CT) development in two chickpea (Cicer arietinum L.) genotypes (Sel96Th11439, cold tolerant, and ILC533, cold susceptible) by using cDNA-amplified fragment length polymorphism (cDNA-AFLP) technique during the first and sixth days of cold stress (CS) at 4 °C. Selective amplification by primer combinations generated 4200 transcript-derived fragments (TDFs) while 100 of them (2.62%) were differentially expressed. During CS, 60 differentially expressed TDFs of TiO2 NPs-treated plants were cloned and 10 of them produced successfully readable sequences. These data represented different groups of genes involved in metabolism pathways, cellular defense, cell connections and signaling, transcriptional regulation and chromatin architecture. Two out of 10 TDFs were unknown genes with uncharacterized functions or sequences without homology to known ones. The network-based analysis showed a gene-gene relationship in response to CS. Quantitative reverse-transcriptase polymerase chain reaction (qPCR) confirmed differential expression of identified genes (six out of 10 TDFs) with potential functions in CT and showed similar patterns with cDNA-AFLP results. An increase in transcription level of these TDFs, particularly on the first day of CS, was crucial for developing CT through decreasing electrolyte leakage index (ELI) content in tolerant plants compared to susceptible ones, as well as in TiO2 NPs-treated plants compared to control ones. It could also indicate probable role of TiO2 NPs against CS-induced oxidative stress. Therefore, a new application of TiO2 NPs in CT development is suggested for preventing or controlling the damages in field conditions and increasing crop productivity.

Effect of TiO2 nanoparticles on chickpea response to cold stress.

Nanoparticles (NPs) in agricultural systems can potentially be used as appropriate candidate for change in growth, development, productivity, and quality of plants. In the present study, we assessed the effect of TiO2 NP concentrations (0, 2, 5, and 10 ppm) on changes of membrane damage indexes like electrolyte leakage index (ELI) and malondialdehyde (MDA) during cold stress (CS) 4 °C in sensitive (ILC 533) and tolerant (Sel 11439) chickpea (Cicer arietinum L.) genotypes. Aggregation of NPs within the vacuole and chloroplast indicated absorbed NPs in seedlings. Bioaccumulation of NPs showed that, under thermal treatments, the sensitive genotype had more permeability to NPs compared to the tolerant one, and TiO2 content was higher during CS compared to optimum temperature. Physiological indexes were positively affected by NP treatments during thermal treatments. TiO2 NP treatments (especially 5 ppm) caused a decrease in ELI during thermal treatments, whereas ELI content under CS treatment increased at 0 ppm TiO2 in both genotypes. Under thermal treatments, although the genotype 11439 showed lower accumulation of MDA than ILC 533 genotype, a significant decrease was observed in MDA content at 5 ppm TiO2. Results showed that TiO2 treatments not only did not induce oxidative damage in sensitive and tolerant chickpea genotypes but also alleviated membrane damage indexes under CS treatment. It was suggested for the first time that TiO2 NPs improved redox status of the genotypes under thermal treatments. New findings possibly would reveal the use of NPs generally or TiO2 NPs especially for increase of cold tolerance in crops.