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Geomagnetic Field (Gmf) and Plant Evolution: Investigating the Effects of Gmf Reversal on <em>Arabidopsis thaliana </em>Development and Gene Expression

One of the most stimulating observations in plant evolution is a correlation between the occurrence of geomagnetic field (GMF) reversals (or excursions) ...

University of Turin

We investigated the role of polyamines (PAs) in lima bean (Phaseolus lunatus) leaves on the production of herbivorous mite (Tetranychus urticae)-induced plant volatiles that attract carnivorous natural enemies of the herbivores. To do this, we focused on the effects of the exogenous PAs [cadaverine, putrescine, spermidine and spermine (Spm)] on the production of volatiles, H(2)O(2) and jasmonic acid (JA) and the levels of defensive genes, cytosolic calcium and reactive oxygen species (ROS). Among the tested PAs, Spm was the most active in inducing the production of volatile terpenoids known to be induced by T. urticae. An increase in JA levels was also found after Spm treatment, indicating that Spm induces the biosynthesis of JA, which has been shown elsewhere to regulate the production of some volatile terpenoids. Further, treatment with JA and Spm together resulted in greater volatile emission than that with JA alone. In a Y-tube olfactometer, leaves treated with Spm + JA attracted more predatory mites (Phytoseiulus persimilis) than those treated with JA alone. After treatment with Spm + JA, no effects were found on the enzyme activity of polyamine oxidase and copper amine oxidase. However, induction of calcium influx and ROS production, and increased enzyme activities and gene expression for NADPH oxidase complex, superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and glutathione peroxidase were found after treatment with Spm + JA. These results indicate that Spm plays an important role in the production of T. urticae-induced lima bean leaf volatiles.

Exogenous polyamines elicit herbivore-induced volatiles in lima bean leaves: involvement of calcium, H2O2 and Jasmonic acid.

Exogenous polyamines [cadaverine (Cad), putrescine (Put), spermidine (Spd) and spermine (Spm)] elicit the production of volatiles in Lima bean (Phaseolus lunatus). Among the tested PAs, Spm induces the production of some volatile terpenoids that are known to be induced by the spider mite Tetranychus urticae. Spm treatment elicits the biosynthesis of Jasmonic acid (JA), a phytohormone known to regulate the production of the volatile terpenoids. The treatment with JA together with Spm resulted in the increased volatile emission, and predatory mites Phytoseiulus persimilis preferred JA and Spm-treated leaves over those treated with JA alone. JA and Spm treatment has no effects on polyamine oxidase (PAO) and Cu-amine oxidase (CuAO) but has a significant induction of calcium influx, ROS production, enzyme activities for NADPH-oxidase complex, superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and glutathione peroxidase, and gene expressions except for NADPH-oxidase complex. Here, we report that a plasma membrane potential (V(m)) depolarization was observed after polyamine perfusion with an increasing trend: Spm, Cad, Put and Spd. JA perfusion did not alter V(m) but the perfusion of JA and the polyamines significantly increased Cad and Put V(m) depolarization. When JA was perfused with polyamines, a negative correlation was found between V(m) depolarization and the number of amino group of the polyamines tested.

Polyamines and jasmonic acid induce plasma membrane potential variations in Lima bean.

Suspension cultured cells of a blast-resistant rice genotype (Oryza sativa L. cv. Gigante Vercelli) were treated with cell wall hydrolysates prepared from the fungal pathogen Magnaporthe oryzae. As a consequence, a complex pattern of phenylalanine ammonia lyase time course specific activity levels was evident. Ion-exchange chromatographic fractionation of crude extracts suggested that the early (6 h) and the late (48-72 h after elicitation) increase of activity relied upon the sequential induction of two different isoenzymes. The relative expression levels of 11 genes putatively coding for a phenylalanine ammonia lyase were measured by semi-quantitative capillary gel electrophoresis of RT-PCR products. Two genes were indeed found to be induced by treatments with the hydrolysate, and data were validated by real-time PCR. Conversely, only the early-responsive enzyme form was observed following elicitation in a blast-sensitive rice genotype (cv. Vialone nano). Therefore, the late-responsive isoform may represent a candidate gene to select for decreased sensitivity to blast.

Ravishankar Narayana

Department of Life Sciences and Systems Biology

University of Turin

Geomagnetic Field (Gmf) and Plant Evolution: Investigating the Effects of Gmf Reversal on Arabidopsis thaliana Development and Gene Expression

Ravishankar Narayana

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Life Sciences and Systems Biology

University of Turin

Geomagnetic Field (Gmf) and Plant Evolution: Investigating the Effects of Gmf Reversal on Arabidopsis thaliana Development and Gene Expression

Department of Life Sciences and Systems Biology