Nitrate affects transcriptional regulation of UPBEAT1 and ROS localisation in roots of Zea mays L.

Nitrogen is an indispensable nutrient for crops but its availability in agricultural soils is subject to considerable fluctuation. Plants have developed plastic responses to external N fluctuations in order to optimise their development. The coordinated action of nitric oxide and auxin seems to allow the cells of the transition zone (TZ) of the root apex of N-deprived maize to rapidly sense nitrate. Preliminary results support the hypothesis that reactive oxygen species (ROS) signalling might also have a role in this pathway, probably through a putative maize orthologue of UPBEAT1 (UPB1). To expand on this hypothesis and better understand the different roles played by different root portions, we investigated the dynamics of ROS production, and the molecular and biochemical regulation of the main components of ROS production and scavenging in tissues of the Meristem, Transition Zone, Elongation Zone and Maturation Zone of maize roots. The results suggest that the inverse regulation of ZmUPB1 and ZmPRX112 transcription observed in cells of the TZ in response to nitrogen depletion or nitrate supply affects the balance between H2O2 and O2 12 in the root apex and consequently triggers differential root growth. This explanation is supported by additional results on the overall metabolic and transcriptional regulation of ROS homeostasis

Superoxide generation catalyzed by the ozone-inducible plant peptides analogous to prion octarepeat motif

Ozone-inducible (OI) peptides found in plants contain repeated sequences consisting of a hexa-repeat unit (YGH GGG) repeated 7–9 times in tandem, and each unit tightly binds copper. To date, the biochemical roles for OI peptides are not fully understood. Here, we demonstrated that the hexa-repeat unit from OI peptides behaves as metal-binding motif catalytically active in the O2•-generation. Lastly, possible mechanisms of the reaction and biological consequence of the reactions are discussed by analogy to the action of human prion octarepeat peptides

Peroxyacetyl nitrate-induced oxidative and calcium signaling events leading to cell death in ozone-sensitive tobacco cell-line

It has long been concerned that some secondary air pollutants such as smog components, ozone (O3) and peroxyacetyl nitrate (PAN), are highly phytotoxic even at low concentrations. Compared with the biology of O3, we largely lack the information on the toxicity model for PAN at the cellular signaling levels. Here, we studied the cell-damaging impact of PAN using suspension culture of smog-sensitive tobacco variety (Bel-W3). The cells were exposed to freshly synthesized PAN and the induced cell death was assessed under microscope after staining with Evans blue. Involvement of reactive oxygen species (ROS) in PAN toxicity was suggested by PAN-dependently increased intracellular H2O2 and also by the cell-protective effects of ROS scavengers and related inhibitors. Calcium chelator also lowered the level of PAN-induced cell death, indicating that Ca2+ is also involved. Using a transgenic cell line expressing aequorin, an increase in cytosolic Ca2+ concentration responsive to the pulse of PAN, but sensitive to Ca2+ channel blockers, was recorded, indicating that Ca2+ channels are activated by PAN or PAN-derived signals. Above data show some similarity between the signaling mechanisms responsive to O3 and PAN