Reactive oxygen species produced by NADPH oxidase regulate plant cell growth

Abstract

Cell expansion is a central process in plant morphogenesis, and the elongation of roots and root hairs is essential for uptake of minerals and water from the soil. Ca2+ influx from the extracellular store is required for (and sets the rates of) cell elongation in roots. Arabidopsis thaliana rhd2 mutants are defective in Ca2+ uptake and consequently cell expansion is compromised--rhd2 mutants have short root hairs and stunted roots. To determine the regulation of Ca2+ acquisition in growing root cells we show here that RHD2 is an NADPH oxidase, a protein that transfers electrons from NADPH to an electron acceptor leading to the formation of reactive oxygen species (ROS). We show that ROS accumulate in growing wild-type (WT) root hairs but their levels are markedly decreased in rhd2 mutants. Blocking the activity of the NADPH oxidase with diphenylene iodonium (DPI) inhibits ROS formation and phenocopies Rhd2-. Treatment of rhd2 roots with ROS partly suppresses the mutant phenotype and stimulates the activity of plasma membrane hyperpolarization-activated Ca2+ channels, the predominant root Ca2+ acquisition system. This indicates that NADPH oxidases control development by making ROS that regulate plant cell expansion through the activation of Ca2+ channels.

NADPH oxidases in lung biology and pathology: Host defense enzymes, and more

“…NOX-dependent Ca 2+ signaling may be mediated by increased voltage-dependent Ca 2+ channel opening, as has been demonstrated in angiotensin II signaling in neural cells (50), in B cell receptor-mediated signaling (51), and during NOX-mediated plant root hair outgrowth (52). In addition, NOXmediated ROS may also induce oxidative cysteine modifications within Ca 2+ channel, as was demonstrated for with respect to activation of the ryanodine receptor (53,54).…”

“…Fig. 1), which are critically involved in cell growth and differentiation and morphogenesis (13,38,52,110,111). Because the airway epithelium is continuously subjected to injury due to environmental stress, it possesses an exceptional capacity to repair itself (112,113), through a coordinated response involving rapid spreading and migration of neighboring cells, cell proliferation and redifferentiation, to restore the original mucociliary epithelium (103,114,115).…”

Functional analysis of barley RAC/ROP G‐protein family members in susceptibility to the powdery mildew fungus

“…Kawasaki et al (1999) provided evidence that OsRAC1 could be a regulator of an NADPH oxidase, as known for RAC2 and RAC1 from mammalian systems (Bokoch and Diebold, 2002). Like RAC/ROP proteins (Li et al, 1999), the NADPH oxidase is involved in ROI production and tip-focused Ca 2 accumulation during polar root hair growth (Foreman et al, 2003). The establishment of Bgh-haustoria in barley epidermal cells requires polar plant membrane growth, and during this process, generation of superoxide at the side of penetration has been detected.…”

Glutathione – linking cell proliferation to oxidative stress

“…The Arabidopsis genome has ten AtRboh genes (AtRbohA-AtRbohJ) that encode NADPH oxidases (59). The activity of NADPH oxidases is required for root growth and for root hair development (60).Auxininduced ROS production is mediated at least in part by the activation of RbohD (58,(60)(61)(62)(63) but RbohC is involved in the control of root hair tip growth(64), a process that also involves the transcriptional Mediator subunits, PFT1/MED25 by activating a subset of hydrogen peroxide-producing class III peroxidases (65). As discussed below, the regulated activities of both NADPH oxidases and peroxidases are required for the orchestration of root development.…”