Positive feedback regulation of maize NADPH oxidase by mitogen-activated protein kinase cascade in abscisic acid signalling

Abstract

In maize (Zea mays), abscisic acid (ABA)-induced H2O2 production activates a 46 kDa mitogen-activated protein kinase (p46MAPK), and the activation of p46MAPK also regulates the production of H2O2. However, the mechanism for the regulation of H2O2 production by MAPK in ABA signalling remains to be elucidated. In this study, four reactive oxygen species (ROS)-producing NADPH oxidase (rboh) genes (ZmrbohA–D) were isolated and characterized in maize leaves. ABA treatment induced a biphasic response (phase I and phase II) in the expression of ZmrbohA–D and the activity of NADPH oxidase. Phase II induced by ABA was blocked by pretreatments with two MAPK kinase (MPKKK) inhibitors and two H2O2 scavengers, but phase I was not affected by these inhibitors or scavengers. Treatment with H2O2 alone also only induced phase II, and the induction was arrested by the MAPKK inhibitors. Furthermore, the ABA-activated p46MAPK was partially purified. Using primers corresponding to the sequences of internal tryptic peptides, the p46MAPK gene was cloned. Analysis of the tryptic peptides and the p46MAPK sequence indicate it is the known ZmMPK5. Treatments with ABA and H2O2 led to a significant increase in the activity of ZmMPK5, although ABA treatment only induced a slight increase in the expression of ZmMPK5. The data indicate that H2O2-activated ZmMPK5 is involved in the activation of phase II in ABA signalling, but not in phase I. The results suggest that there is a positive feedback loop involving NADPH oxidase, H2O2, and ZmMPK5 in ABA signalling.

Changes in Hydrogen Peroxide Levels and Catalase Isoforms Expression are Induced with Freezing Tolerance by Abscisic Acid in Potato Microplants

“…CAT2 transcripts and the relevant isozyme were strongly ABA-inducible. Given the increased H 2 O 2 levels in ABA-treated microplants, and the H 2 O 2 -inducibility of potato CAT2 (Almeida et al, 2005), this gene may have an ABA-induction mechanism like Arabidopsis CAT1 (Xing et al, 2008) and maize CAT1 (Lin et al, 2009). Our data are consistent with potato CAT2 as the ortholog of the stress-inducible N. plumbaginifolia CAT2 (Willekens et al, 1994;Santos et al, 2006).…”

“…The origin of H 2 O 2 induced by ABA has been identified as superoxide generation by plasma membrane NADPH oxidases, encoded by Rboh (respiratory burst oxidase homolog) genes (Cho et al, 2009). Recent work in maize indicates that the ABA-induced expression and activity of NADPH oxidases is further stimulated by the resultant H 2 O 2 in a MAPK-regulated positive feedback (Lin et al, 2009). …”

Hemoglobin Control of Cell Survival/Death Decision Regulates in Vitro Plant Embryogenesis

“…All genes, with expression patterns that correlate to the activation of NADPH oxidase (Lin et al, 2009a), were induced in lines suppressing ZmHb1(A) and ZmHb2(A) in a fashion consistent with a regulation mediated by NO and Zn 2+ (Supplemental Fig. S8).…”

Lysigenous aerenchyma formation in maize root is confined to cortical cells by regulation of genes related to generation and scavenging of reactive oxygen species

“…8,9,12 Several studies have shown that transcriptional activation of RBOH genes is accompanied by an oxidative burst, [12][13][14] and the positive feedback regulation of the RBOH gene expression at transcriptional and post-transcriptional levels contributes to amplification of the ROS signals. 12,[15][16][17] There is increasing evidence that plant MTs regulate the accumulation of ROS: downregulation of the rice MT2b gene contributed to high H 2 O 2 accumulation during defense signaling 18 and ethylene-induced epidermal cell death, 19 and H 2 O 2 treatment and knockdown of MT2b gene promoted lysigenous aerenchyma formation the subsequent processes of PCD and lysis of the cortical cells (i.e., lysigenous aerenchyma formation) in maize roots.…”