Effects of Cor15a-IPT Gene Expression on Leaf Senescence in Transgenic Petunia x hybrida and Dendranthema x grandiflorum.

To prevent leaf senescence of young transplants or excised shoots during storage under dark and cold conditions, the cytokinin biosynthetic gene isopentenyl transferase (ipt) was placed under the control of a cold-inducible promoter cor15a from Arabidopsis thaliana and introduced into Petunia x hybrida \u27Marco Polo Odyssey\u27 and Dendranthema x grandiflorum (chrysanthemum) \u27Iridon\u27. Transgenic cor15a-ipt petunia and chrysanthemum plants and excised leaves remained green and healthy during prolonged dark storage (4 weeks at 25 degrees C) after an initial exposure to a brief cold-induction period (4 degrees C for 72 h). However, cor15a-ipt chrysanthemum plants and excised leaves that were not exposed to a cold-induction period, senesced under the same dark storage conditions. Regardless of cold-induction treatment, leaves and plants of non-transformed plants senesced under prolonged dark storage. Analysis of ipt expression indicated a marked increase in gene expression in intact transgenic plants as well as in isolated transgenic leaves exposed to a short cold-induction treatment prior to dark storage. These changes correlated with elevated concentrations of cytokinins in transgenic leaves after cold treatment. Cor15a-ipt transgenic plants showed a normal phenotype when grown at 25 degrees C

A different pattern of production and scavenging of reactive oxygen species in halophytic Eutrema salsugineum (Thellungiella salsuginea) plants in comparison to Arabidopsis thaliana and its relation to salt stress signaling

Isolated thylakoids from halophytic Eutrema salsugineum (Thellungiella salsuginea) produces more H2O2 in comparison to glycophytic Arabidopsis thaliana. The first objective of this study was to verify whether this feature is relevant also to the intact chloroplasts and leaves. Enhanced H2O2 levels in chloroplasts and leaves of E. salsugineum were positively verified with several methods (electron microscopy, staining with Amplex Red and with diaminobenzidine). This effect was associated with a decreased ratio of O2.-/H2O2 in E.s in comparison to A.thaliana as detected by electron paramagnetic resonance (EPR) method. As a next step, we tested how this specific ROS signature of halophytic species affect the antioxidant status and down-stream components of ROS signaling. Comparison of enzymatic antioxidants revealed a decreased activity of ascorbate peroxidase (APX), enhanced activity of glutathione peroxidase (GPX), and the presence of thylakoid-bound forms of iron superoxide dismutase (FeSOD) and ascorbate peroxidase (APX) in E.s.. These cues were, however, independent from application of salt stress. The typical H2O2-dependent cellular responses, namely the levels of glucosinolates and stress-related hormones were determined. The total glucosinolate content in E.s water-treated leaves was higher than in A.t. and increased after salinity treatment. Treatment with salinity up-regulated all of tested stress hormones, their precursors and catabolites (abscisic acid, dihydrophaseic acid, phaseic acid, 1-aminocyclopropane-1-carboxylic acid, salicylic acid, jasmonic acid, cis-(+)-12-oxo-phytodienoic acid and jasmonoyl-L-isoleucine) in A.t., whereas in E.s. only a stimulation in ethylene synthesis and abscisic acid catabolism was noted. Obtained results suggest that constitutively enhanced H2O2 generation in chloroplasts of E.s. might be a crucial component of stress-prepardeness of this halophytic species. It shapes a very efficient antioxidant protection (in which glucosinolates might play a specific role) and a fine tuning of hormonal signaling to suppress the cell death program directed by jasmonate pathway

The mvp2 mutation affects the generative transition through the modification of transcriptome pattern, salicylic acid and cytokinin metabolism in Triticum monococcum

Wild type and mvp2 (maintained vegetative phase) deletion mutant T. monococcum plants incapable of flowering were compared in order to determine the effect of the deleted region of chromosome 5A on transcript profile and hormone metabolism. This region contains the vernalizationl (VRN1) gene, a major regulator of the vegetative/generative transition. Transcript profiling in the crowns of T. monococcum during the transition and the subsequent formation of flower primordia showed that 306 genes were affected by the mutation, 198 by the developmental phase and 14 by the interaction of these parameters. In addition, 546 genes were affected by two or three factors. The genes controlled by the deleted region encode transcription factors, antioxidants and enzymes of hormone, carbohydrate and amino acid metabolism. The observed changes in the expression of the gene encoding phenylalanine ammonia lyase (PAL) might indicate the effect of mvp2 mutation on the metabolism of salicylic acid, which was corroborated by the differences in 2-hydroxycinnamic acid and cinnamic acid contents in both of the leaves and crowns, and in the concentrations of salicylic acid and benzoic acid in crowns during the vegetative/generative transition. The amount and ratio of active cytokinins and their derivatives (ribosides, glucosides and phosphates) were affected by developmental changes as well as by mvp2 mutation, too. (C) 2016 Elsevier GmbH. All rights reserved

Recovery from drought stress in tobacco: An active process associated with the reversal of senescence in some plant parts and the sacrifice of others

Plant response to water deficit and subsequent re-watering is fine tuned at the whole plant level. It differs not only between shoot and root, but also among particular leaves along a plant axis. We estimated the expression of proline metabolism-related genes and the activity of senescence-related promoter in roots and individual leaves of tobacco plants in the course of drought stress and recovery. Proline plays the dual role of an osmoprotectant and an antioxidant under water deficit. High proline concentration in the youngest uppermost leaves contributed to their protection from drought, which was associated with low degree of senescence. During recovery, elevated proline concentrations persisted and the senescence-related promoter was switched off in all surviving leaves. Two mutually exclusive scenarios were followed by tobacco leaves on recovery—restoration of photosynthesis and metabolism, or death, depending on the progress of senescence

Gliding Arc Plasma Treatment of Maize (Zea mays L.) Grains Promotes Seed Germination and Early Growth, Affecting Hormone Pools, but Not Significantly Photosynthetic Parameters

Maize grains (Zea mays convar. Indentata Sturt.) were treated with non-thermal plasma, where Gliding Arc plasma discharge at an atmospheric pressure was used (working gas: Air; time duration: 0 s, 180 s, 300 s, 600 s). The experiment was conducted at a temperature of 18 °C, light/dark 12/12 h, and a light intensity of 100 µmol/m2s. Seed germination, seedling growth, photosynthetic parameters, and hormone (abscisic acid, jasmonic acid, salicylic acid, indole-3-acetic acid, and cytokinin) contents were measured. The highest stimulation of seed germination (to 141%), root length (to 221%), shoot length (to 298%), and root weight (to 122%) in comparison with the control was recorded after Gliding Arc plasma treatment for 600 s. The photochemical and non-photochemical Chl fluorescence parameters were not significantly affected by Gliding Arc plasma treatment. In contrast, hormonal pools in maize were significantly affected. The short-term plasma treatment (180 s) was associated with a decrease in the stress hormones abscisic acid, salicylic acid, jasmonic acid, and jasmonate isoleucine, while indole-3-acetic acid and cytokinin precursors were elevated. Longer-term treatment (300 s, 600 s) had an opposite effect—an elevation of abscisic acid, jasmonic acid, and jasmonate isoleucine as well as active cytokinins. The content of auxin decreased. Gliding plasma treatment may significantly affect maize physiology, dependent on the treatment duration

Redox control of plant growth and development

Redox changes determined by genetic and environmental factors display well-organized interactions in the control of plant growth and development. Diurnal and seasonal changes in the environmental conditions are important for the normal course of these physiological processes and, similarly to their mild irregular alterations, for stress adaptation. However, fast or large-scale environmental changes may lead to damage or death of sensitive plants. The spatial and temporal redox changes influence growth and development due to the reprogramming of metabolism. In this process reactive oxygen and nitrogen species and antioxidants are involved as components of signalling networks. The control of growth, development and flowering by reactive oxygen and nitrogen species and antioxidants in interaction with hormones at organ, tissue, cellular and subcellular level will be discussed in the present review. Unsolved problems of the field, among others the need for identification of new components and interactions in the redox regulatory network at various organization levels using systems biology approaches will be also indicated. © 2013 Elsevier Ireland Ltd