Stress In Bean Research Articles

Effect of salt stress on growth, chlorophyll content, lipid peroxidation and antioxidant defence systems in Phaseolus vulgaris L.

Salinity is one of the major abiotic stresses which affects plant cell metabolism and reduces plant productivity. Variations in the antioxidant defence systems under salinity among two bean genotypes were investigated. Our results indicate that the difference between the genotypes in response to salinity is a quantitative trait rather than qualitative since they develop the same strategies with a significant variation in the rate of synthesis and accumulation, with the exemption of the antioxidant defence based on the synthesis of phenolic compounds. For both genotypes, salinity induced a marked reduction in dry matter gain in roots and shoots along with oxidative stress as indicated by the significant increase in malondialdehyde content. In addition, the photosynthetic pigments decreased with the increase of salinity. The only qualitative difference that we found among both genotypes was the decrease of total production of phenolic compounds in leaves that was only detectable in the low-yielding genotype under high salinity. The high-yielding genotype may have a better protection against oxidative damages by increasing the activity of antioxidant enzymes and the amounts of total flavonoids and ascorbic acid under high salinity, which allows maintaining higher yield even upon stress conditions. These results indicate that salt induced oxidative stress in bean is mainly counteracted by enzymatic defence systems, and that the metabolism of phenolic compounds is induced under very extreme conditions. The selection of genotypes for this trait will increase yield under stress conditions.

Molecular cloning and characterization of the ABA-specific glucosyltransferase gene from bean (Phaseolus vulgaris L.)

Levels of the plant hormone abscisic acid (ABA) are maintained in homeostasis by a balance of its biosynthesis, catabolism and conjugation. The detailed molecular and signaling events leading to strict homeostasis are not completely understood in crop plants. In this study, we obtained cDNA of an ABA-inducible, ABA-specific UDP-glucosyltransferase (ABAGT) from the bean plant (Phaseolus vulgaris L.) involved in conjugation of a glucose residue to ABA to form inactive ABA-glucose ester (ABA-GE) to examine its role during development and abiotic stress in bean. The bacterially expressed PvABAGTase enzyme showed ABA-specific glucosylation activity in vitro. A higher level of the PvABAGT transcript was observed in mature leaves, mature flowers, roots, seed coats and embryos as well as upon rehydration following a period of dehydration. Overexpression of 35S::PvABAGT in Arabidopsis showed reduced sensitivity to ABA compared with WT. The transgenic plants showed a high level of ABA-GE without significant decrease in the level of ABA compared with the wild type (WT) during dehydration stress. Upon rehydration, the levels of ABA and phaseic acid (PA) decreased in the WT and the PvABAGT-overexpressing lines with high levels of ABA-GE only in the transgenic plants. Our findings suggest that the PvABAGT gene could play a role in ABA homeostasis during development and stress responses in bean and its overexpression in Arabidopsis did not alter ABA homeostasis during dehydration stress.

Effects of Exogenous Salicylic Acid on the Antioxidative System in Bean Seedling Treated with Manganese

In the present study we investigated the role of salicylic acid (SA) in regulating Mn-induced oxidative stress in bean (Phaseolus vulgaris) leaves. Exposure of plants to 100 μM Mn inhibited biomass production and intensively increased Mn accumulation in leaves. Concomitantly, Mn significantly enhanced protein carbonyl, H2O2 content and lipid peroxidation as indicated by malondialdehyde (MDA) accumulation. SA (10, 50 and 100 μM) pretreatment alleviated the negative effect of Mn on plan growth and led to decrease in oxidative stress induced by Mn stress. Furthermore, SA enhanced the activities of catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), but lowered that of superoxide dismutase (SOD, EC 1.15.1.1) and guaiacol peroxidase (POD, EC Original Research Article Saidi et al.; BBJ, 6(3): 93-100, 2015; Article no.BBJ.2015.031 94 1.11.1.7). The data suggest that the beneficial effect of SA could be related to avoidance of oxidative damage upon exposure to Mn thus reducing the negative consequences of oxidative stress caused by Mn toxicity.

Incomplete alleviation of nickel toxicity in bean by nitric oxide supplementation

The aim of the experiment was to test the capacity of NO to reverse harmfull effects of nickel on bean (Phaseolus vulgaris L.) seedlings. Bean seedlings were grown on culture medium and treated with NO-donor – sodium nitroprusside (0.3 mmol/L) and Ni (0.2 mmol/L NiCl<sub>2</sub>). After 4 days, the parameters of antioxidative response were determined in roots and leaves, as well as the concentrations of essential cations and Ni. In the presence of Ni alone, soluble protein, proline and superoxide-dismutase activity were increased, while peroxidase and especially catalase activities were supressed. Also, Ni induced a depletion of K, Ca, Mg, Mn and Zn, while the contents of Cu and Fe in the roots were increased. In the presence of NO, Ni-induced stimulation of superoxide-dismutase activity, soluble protein and proline accumulations was decreased, while the inhibition of peroxidase and catalase activities was eliminated. Calcium and Zn concentrations were increased by Ni in NO-treated seedlings, suggesting specific activation of the uptake of these elements as part of the protective processes regulated by NO. However, NO had no effect on the impact of Ni on K, Cu, Fe, and Mn concentrations. In conclusion, exogenous NO efficiently attenuates oxidative stress in bean, but does not prevent Ni-induced ion leakage.

Gel‐based proteomics reveals potential novel protein markers of ozone stress in leaves of cultivated bean and maize species of Panama

We examined responses of cultivated bean (Phaseolus vulgaris L. cv. IDIAP R-3) and maize (Zea mays L. cv. Guarare 8128) plants exposed to ozone (O(3)) using a leaf injury assessment and proteomics approach. Plants grown for 16 days in greenhouse were transferred to an O(3) chamber and exposed continuously to 0.2 ppm O(3) or filtered pollutant-free air for up to 72 h. CBB-stained gels revealed changes in ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) protein. By Western analysis changes in marker proteins for O(3) damage in leaves by 1-DE were checked. In bean leaves, two superoxide dismutase (SOD) protein (19 and 20 kDa) were dramatically decreased, while ascorbate peroxidase (APX, 25 kDa), small heat shock protein (HSP, 33 kDa), and a naringenin-7-O-methyltransferase (NOMT, 42 kDa) were increased by O(3). In maize leaves, expression levels of catalase (increased), SOD (decreased), and APX (increased) were drastically changed by O(3) depending on the leaf stage, whereas crossreacting HSPs (24 and 30 kDa) and NOMT (41 kDa) proteins were strongly increased in O(3)-stressed younger leaves. These results indicated a clear modulation of oxidative stress-, heat shock-, and secondary metabolism-related proteins by O(3). Finally, 2-DE at 72 h after O(3) exposure revealed changes (induction/suppression) in expression levels of 25 and 12 protein spots in bean and maize leaves, respectively. Out of these, ten and nine nonredundant proteins in bean and maize, respectively, were identified by MS. A novel pathogenesis-related protein 2 may serve as a potential marker for O(3) stress in bean.

Reactive oxygen intermediates and glutathione regulate the expression of cytosolic ascorbate peroxidase during iron-mediated oxidative stress in bean.

Excess of free iron is thought to harm plant cells by enhancing the intracellular production of reactive oxygen intermediates (ROI). Cytosolic ascorbate peroxidase (cAPX) is an iron-containing, ROI-detoxifying enzyme induced in response to iron overload or oxidative stress. We studied the expression of cAPX in leaves of de-rooted bean plants in response to iron overload. cAPX expression, i.e., mRNA and protein, was rapidly induced in response to iron overload. This induction correlated with the increase in iron content in leaves and occurred in the light as well as in the dark. Reduced glutathione (GSH), which plays an important role in activating the ROI signal transduction pathway as well as in ROI detoxification, was found to enhance the induction of APX mRNA by iron. To determine whether cAPX induction during iron overload was due to an increase in the amount of free iron, which serves as a co-factor for cAPX synthesis, or due to iron-mediated increase in ROI production, we tested the expression of APX in leaves under low oxygen pressure. This treatment, which suppresses the formation of ROI, completely abolished the induction of cAPX mRNA during iron overload, without affecting the rate of iron uptake by plants. Taken together, our results suggest that high intracellular levels of free iron in plants lead to the enhanced production of ROI, which in turn induces the expression of cAPX, possibly using GSH as an intermediate signal. We further show, using cAPX-antisense transgenic plants, that cAPX expression is essential to prevent iron-mediated tissue damage in tobacco.

Isoflavonoid Formation as an Indicator of UV Stress in Bean (Phaseolus vulgaris L.) Leaves

Induction of the isoflavonoid pigment, coumestrol (3,9-dihydroxy-6H-benzofuro-[3,2-c][1] benzopyran-6-one), in primary leaves of beans (Phaseolus vulgaris L. var Saxa) by ultraviolet (UV) radiation was used as a quantifiable marker for UV damage to a plant system. Coumestrol was induced only by wavelengths below 300 nanometers and its formation could be reversed by treatment with white, but not red light after the UV irradiation period. Formation of coumestrol by UV could also be prevented over a period of 14 hours by simultaneous irradiation with blue light provided that the blue fluence rate was high enough. The results suggest that coumestrol formation is mediated via UV-induced pyrimidine dimer formation in the plant DNA and the photorepair properties of blue light are discussed with respect to possible increases in solar UV due to stratospheric ozone depletion.