New insights into an old story

Abstract

ROS is a collective term that includes oxygen radicals (e.g., superoxide, hydroxyle, hydroperoxyle), and certain non radicals (e.g., H 2 O 2 , ozone, singlet oxygen) that are oxidising agents and/or are easily converted into radicals. These agents are continuously produced in plants and other aerobic organisms as a result of partial O 2 reduction during a number of normal metabolic processes, such as respiration, photosynthesis and photorespiration. [1][2][3][4] The ROS pool size depends on the relative rates of ROS generation and destruction, and on the life time of the main ROS species. Plants possess a complex battery of ROS scavenging enzymes (e.g., superoxide dismutase, ascorbate peroxidase, glutathione peroxidase and catalase), and low molecular non-enzymatic antioxidants (e.g., ascorbate and glutathione, but also tocopherol, flavonoids, alkaloids and carotenoids), often confined to particular compartments, that play a key role in ROS cellular control levels. 5,6 Excess ROS is harmful to many plant cell constituents, including lipids, proteins and nucleic acids, and in some case can induce plant cell death. 7,8 Several biochemical and genetic studies have emphasized the key role of ROS as PCD (apoptosis) triggers in plant cell response to specific stimuli.9,10 PCD controlled by ROS occurs during developmental processes, including aleurone cell death and leaf senescence, hypersensitive response, allelopathic plantplant interactions, and various forms of abiotic stress. 6,11,12 External adverse conditions (high light, drought, low and high temperature and mechanical stress) disrupt intracellular ROS Reactive oxygen species (ROS) can exhibit negative and benign traits. In plants, ROS levels increase markedly during periods of environmental stress and defense against pathogen attack. ROS form naturally as a by-product of normal oxygen metabolism, and evenly play an essential role in cell growth. The short ROS lifespan makes them ideal molecules to act in cell signaling, a role they share in both plants and animals. A particular plant organism, the pollen grain, may closely interact with human mucosa and an allergic inflammatory response often results. Pollen grain ROS represent a first, crucial signal which primes and magnifies a cascade of events in the allergic response. New insights into an old storyPollen ROS also play a role in hay fever Keywords: NADPH oxidase, reactive oxygen species, pollen, allergy, oxidative stress, environment pollution homeostasis.6 Interestingly, ROS/redox signaling networks in the chloroplast and mitochondria play essential roles in plant acclimation to abiotic stress via the regulation of important biological pathways, such as gene expression, energy metabolism and protein phosphorylation. 13Until recently, ROS were considered unwelcome by-products of metabolism. However, information continues to emerge on the range of ROS forms, and has demonstrated the molecules serve as important plant development and growth regulators, which operate in strict association with hormonal signal...

Proteomic Analysis of MG132-Treated Germinating Pollen Reveals Expression Signatures Associated with Proteasome Inhibition

“…At high concentrations ROS causes damage to biomolecules, whereas at low/moderate concentrations it acts as a second messenger in intracellular signaling cascades that mediate several responses in plant cells. ROS levels play an important role in pollen tube emergence and elongation and must be strictly regulated [46] , [47] . Thus, ROS over-accumulation induced by proteasome inhibition may contribute to the observed inhibition of pollen germination and tube elongation.…”

A Review of the Effects of Major Atmospheric Pollutants on Pollen Grains, Pollen Content, and Allergenicity

“…Zea m 1 has indeed a large effect on pollen tube growth rates in vivo [ 91 ]. It is also known that formation of reactive oxygen species (ROS) in pollen starts at the early germination stage, before the formation of the pollen tube, generated mainly by NAD(P)H oxidases, in insoluble fractions [ 92 – 95 ]. Thus pollen viability, pollen germination, allergenicity, and air pollution effects on pollen could have some important common points.…”