فهرست مطالب مریم پسندیده ارجمند

This study was conducted for investigating the effect of drought different levels on morphological and physiological traits of Canola and investigating relative expression of antioxidant genes to identify the antioxidant response of tolerant genotype at drought different levels. The factorial experiment based on unbalanced completely random design was conducted at the end of the 5-leaf stage of Canola in 3 replications in the greenhouse of Agricultural Sciences Faculty of Gilan University on the year 2022. The effect of different drought levels, including non-stress (100%), low (75%), medium (50%), severe (25%) and very severe stress (20%FC) on morphological and physiological traits in SLM046 and Licord Canola genotypes, as well as the relative expression of important antioxidant genes of Ferredoxin-NADP+oxidoreductase (FNR) and NADPH-thioredoxin reductase (NTR) in the tolerant genotype were investigated using Real-time PCR based on Livak method. The interaction effect of stress on genotype for root length, shoot and root dry weight, allometric coefficient, root water weight, chlorophyll a and b, total chlorophyll, carotenoid and anthocyanin was significant at 1% probability level. The allometric coefficient at 20%FC, and root dry weight at all levels were higher in SLM046 than Licord under drought stress. Drought stress caused a decrease in RWC at 75% FC in both genotypes. Also, the drough treatment at the level of 20% FC caused a decrease in the leaf area and the treatment of all stress levels caused a decrease in the amount of anthocyanin in both genotypes. The stress treatment at 20%FC increased the amount of chlorophyll b and total chlorophyll in SLM046 genotype. The treatment at all stress levels decreased the chlorophyll a and b, total chlorophyll and carotenoid in Licord genotype. The results showed that the expression of FNR and NTR genes increased in SLM046 genotype at higher stress levels. It seems that the SLM046 is tolerant under severe and very severe drought. The increase in FNR expression, which leads to the production of NADPH, is regulated by the NTR expression, and by regulating the expression of genes involved in oxidative stress, it can cause drought tolerance and plant survival in tolerant genotype.

MicroRNAs (miRNAs) are small, non-coding, and regulatory molecules that play an important role in post gene expression regulation in response to biotic and abiotic stresses. Although Canola (Brassica napus) is a globally important oilseed, little is known about its regulation mechanisms target genes of drought-responsive miRNAs. Then, in this study drought-responsive miRNAs target genes of bna-miR156b, bna-miR156c, bna-miR156g, bna-miR171a, bna-miR171d, bna-miR171e, bna-miR172d, bna-miR399a, bna-miR399b, bna-miR396a, bna-miR395d, bna-miR395e and bna-miR395f in Canola were identified by bioinformatics tools. Molecular function, biological process, cellular component, proteins interaction, and relation of their pathways were investigated. In the present study were identified 225 target genes for miRNAs. Bioinformatics study showed that ribosome, proteasome, and chaperon-related genes of RPP1C, RPL36AA, RPL9D, RPS11, RPT1A, RPT2a, RPT4A, RPN11, HSF1, HSFA1E, HSF4, and HSFB2B are targets of drought-responsive miRNAs of bna-miR172d ،bna-miR156b/c/g، bna-miR860، bna-miR396a and bna-miR395d. Ribosomes, proteasomes, and chaperons are regulated by drought-responsive miRNAs for protein regulation and stress tolerance under drought conditions. Laboratory study of identified genes in this study can be a fundamental step in the production of drought-resistant Canola cultivars in inbreeding and genetic engineering programs.

Plants are often exposed to a variety of environmental stresses such as drought and salinity, which leads to osmotic stress in the plant and ultimately reduces crop growth and productivity. Identification of effective genes at different treatments of osmotic stress can be very helpful in finding genes that are effective in tolerating plant stresses. Therefore, the aim of this study was to identify the hub genes of Arabidopsis model plant in osmotic stress and to introduce them for crop breeding under environmental stresses .

In this study, Arabidopsis microarray data that were exposed to mannitol-induced osmotic stress for 1.5, 3, 12 and 24 hours were analyzed separately by GEO2R online tool. Genes with significant expression were identified and the most important genes at each stress level were identified using bioinformatics tools. Then, the hub genes in osmotic stress were identified and their protein interactions and biological processes were studied and discussed .

The result showed that 26, 79, 138 and 184 genes had significant expression at 1.5, 3, 12 and 24 hours after stress, respectively. Based on protein network analysis and biological processes, SDA1, CRK11, CYP81F2, EDA39, PLA2A, T1K7_24, F6N7_24, AT2G25735 and MRH10_18 genes were reported as hub genes at different levels of osmotic stress. The results of molecular function analysis of hub genes showed that these genes involved in oxidative stress, response to hypoxia, regulation stomata movement, hypersensitive response, response to chitin, induced systemic resistance, indole glucosinolate biosynthetic process, defense response by callose deposition in cell wall, response to cadmium ion, phytochelatin biosynthetic process, arsenite transport, defense response to bacteria, insects, fungi, viruses and other environmental stress responsive biological process. 

It seems that the key genes introduced in this study can be used to breed crops under environmental stresses that cause osmotic stress in plants.

Iron toxicity lead to oxidation of photosynthetic pigments, increasing of free radicals and as a result rice yield to be severely damaged. This study was performed to investigate the effect of iron toxicity on relative expression of alternative oxidase, external alternative NAD(P)H-ubiquinone oxidoreductase, internal alternative NAD(P)H-ubiquinone oxidoreductase, NADH dehydrogenase, NATPH-thioredoxin reductase and ferredoxin-thioredoxin reductase genes in two rice genotypes, IR64 (susceptible) and Pokkali (tolerant). Iron ion was applied at the levels of 0 (check), 100, 250, 400 and 500 mg.lit-1 under Yoshida hydroponic conditions. Results showed that the iron cosentration in leaves increased with increasing of stress levels. There was not a significant difference among IR64 treatments samples for leaves potassium cosentration. But it increased in Pokkali genotype relative to non stress samples .The expression levels of genes in Pokkali except NDH and IN-NDH in 250 and 400 mg li-1 and NTR in 500 mg li-1 samples were higher than IR64. In all, the difference of morphological traits and relative over expression of genes in Pokkali. In all, the difference of morphological traits and relative over expression of genes in Pokkali indicated that the gene could considerably effect on the tolerant level of pokkali by reducing ROS production under Fe-toxicity. Our results showed that high activity of the mitochondrial and genes, alone or together, could also be an important factor in iron tolerance in rice by detoxifying the harmful effects of the ROS.

Under the iron toxicity conditions, one of the most important limiting factors of rice production in agricultural lands is the increase of active oxygen radicals and thus decrease of plant growth and development. In this study, the effect of iron induced toxicity at 0 (control), 100, 250, 400 and 500 mg/l (Fe-EDTA) levels were investigated on some morphological traits, relative expression of G6PDH photosynthetic gene and activity of peroxidase enzyme in two rice genotypes, Pokkali (tolerant) and IR64 (susceptible), at four-leaf growth stage under hydroponic conditions with Yoshida nutrient solution. The experiment was carried out as factorial with two factors, genotype and iron concentration (two and five levels, respectively), in a completely randomized deshgn with three replications. The results showed that the interaction of iron toxicity and genotype had significant effect on all studied traits except root dry weight. Cluster analysis using farthest neighbor divided the ten studied treatments into two separate groups. Principal component analysis showed also that 66% of the total variation was explained by two principal components. Applying iron toxicity stress reduced the relative expression of G6PDH gene in both genotypes, exept that the relative expression of this gene in the Pokkali genotype decreased with the application of low stress levels, but in the IR64 genotype, the decrease in expression of this gene observed only at high stress levels. The lowest activity of peroxidase enzyme was observed in both Pokkali and IR64 genotypes at 100 mg/l iron and the highest activity were observed at 400 and 250 mg/l, respectively. It seems that decreasing the expression of G6PDH gene at low stress levels and increasing the activity of peroxidase enzyme in the tolerant genotype can reduce the amount of hydrogen peroxide induced by iron toxicity.

Iron toxicity lead to increasing of free oxygen radicals, oxidative stresses and sever yield reduction of Rice. One of the plant responses for physiochemical and biochemical regulation to stresses is change of antioxidant enzyme contents. In this study the effect of five treatments of iron (Fe-EDTA) (0, 100, 250, 400 and 500 mg/li-1) on relative expression of glutaredoxin (GRX), thioredoxin (TRX), peroxiredoxin (PRX) and catalase (CAT) genes of IR64 (susceptible) and Pokkali (tolerant) genotypes of Rice in Yoshida hydroponic media by Real time-PCR technique investigated. The results showed that the relative expression level of CAT gene in different levels of iron in Pokkali genotype was higher than IR64 genotype. The relative expression level of PRX in IR64 genotype in all of the levels was similar. The relative expression level of TRX in Pokkali genotype was not significant. The relative expression level of GRX in the most of stress levels in Pokkali genotype was higher than IR64 genotype. Low level iron result in increasing of relative expression level of CAT, GRX and TRX in IR64 genotype. But with increasing level of iron was not significant change in expression of genes. Also in the most of the iron level relative expression of genes in Pokkali was higher than IR64. Probably lose of change in gene expression levels in high level iron and low gene expression in IR64 is one of the reasons of its susceptibility to iron stress.

Increasing of reactive oxygen species (ROS) under iron toxicity is considered as one of the major constraints to rice production. In this study the alterations of SOD, GPX1 and MDHR expression level in two genotypes of rice, Pokkali (as tolerant) and IR64 (as sensitive) were monitored under different concentrations of iron levels [(0) (nonstress)], 100, 250, 400 and 500 mg/lit-1Fe-EDTA). The treatments were done when the plants were at 4-leaf stage and lasted for two weeks. Results showed that the expression levels of genes in Pokkali were higher than IR64. The expression level of SOD in IR64, increased at iron concentration increased, while it decreased at higher Fe-level. The expression level of GPX1 was increased in IR64, but decreased in Pokkali. The expression level of MDHR in IR64 was decreased at early stage of Fe-treatment, but then increased. Inversely, in Pokkali MDHR expression reduced constantly under Fe stress. Overall, the relative over expression of genes in Pokkali and presence of different expression levels of them between different concentrations of Fe in tolerant and sensitive genotypes indicate that the gene could remarkably effect on the tolerant level of pokkali by reducing ROS production under Fe-toxicity.

In order to study some morphological and physiological traits of susceptible (Hayola308) and tolerant (SLM046) genotypes of canola to drought stress, an experiment was conducted in CRD design with factorial split in time arrangement. The applied factors were genotype (susceptible and tolerant) and irrigation condition (non-stress and stress). The stress was applied at before flowering time and the traits were measured at 24, 48, 72 and 96 hours after it in both condition. The result showed a reduction in dry weight of root in Hayola308 genotype, and a significant increase in root to shoot length ratio, fresh weight of root and malondialdehyde level (MDA) in SLM046 genotype. The 48 hours after drought stress, the fresh weight of shoot in SLM046 genotype was higher than Hayola308 genotype. Relative water content (RWC) in SLM046 and Hayola308 at 24 hours after stress were 88.59% and 38.52%, respectively. In Hayola308 genotype, hydrogen peroxide (H2O2) content in stress condition was higher than non-stress ones. There was not a significant difference among studied treatments for electrolyte leakage. In general, the increase of root length, root to shoot length ratio, RWC, fresh weight of root and the difference between fresh and dry weight of root and shoot and no change in dry weight of root and H2O2 content in SLM046 genotype indicated that this genotype had traits which could assign tolerance to drought stress.

Drought is one of the most devastating environmental stresses that adversely affect plant metabolic processes. Many plant genes such as photorespiration ones are involve in response to drought stress. In the present study, the effects of drought stress on the expression level of two peroxisomal (Hydroxy pyruvate reductase (HPR1) and Glycolate oxidase (GO)) and two mitochondrial (Serine hydroxy methyl transferase (SHMT) and Glycine decarboxylase (GDC)) genes were studied in susceptible (Hayola308) and tolerant (SLM046) genotypes of canola (Brassica napus) under stress (irrigation cut at flowering stage) and non-stress conditions. The result of real time-PCR showed that in Hyola308 genotype the expression level of GO gene at 48, 72 and 96 hours after stress was higher than SLM046 genotype. In Hyola308 genotype, the highest expression level of GDC gene observed at 48 hours of stress and then decreased. The highest relative expression level of SHMT gene in both Hyola308 and SLM046 genotypes detected at 24 hours after stress and then in SLM046 genotype, its level decreased at 48 hours after stress, while in Hyola308 genotype, its expression declined over the time of exposure to stress. SLM046 genotype showed highest amount of HPR1 expression level at 48 hours after stress. It seems that the expression of photorespiration genes in SLM046 genotype increased at the initial times of exposure to stress and with continue the stress, it showed more adaptation to stress and control the photorespiration unlike Hyola308.