A Raf-Like MAPKKK Gene DSM1 Mediates Drought Resistance through Reactive Oxygen Species Scavenging in Rice      

Abstract

Mitogen-activated protein kinase (MAPK) cascades have been identified in various signaling pathways involved in plant development and stress responses. We identified a drought-hypersensitive mutant (drought-hypersensitive mutant1 [dsm1]) of a putative MAPK kinase kinase (MAPKKK) gene in rice (Oryza sativa). Two allelic dsm1 mutants were more sensitive than wildtype plants to drought stress at both seedling and panicle development stages. The dsm1 mutants lost water more rapidly than wild-type plants under drought stress, which was in agreement with the increased drought-sensitivity phenotype of the mutant plants. DSM1-RNA interference lines were also hypersensitive to drought stress. The predicted DSM1 protein belongs to a B3 subgroup of plant Raf-like MAPKKKs and was localized in the nucleus. By real-time PCR analysis, the DSM1 gene was induced by salt, drought, and abscisic acid, but not by cold. Microarray analysis revealed that two peroxidase (POX) genes, POX22.3 and POX8.1, were sharply down-regulated compared to wild type, suggesting that DSM1 may be involved in reactive oxygen species (ROS) signaling. Peroxidase activity, electrolyte leakage, chlorophyll content, and 3,3#-diaminobenzidine staining revealed that the dsm1 mutant was more sensitive to oxidative stress due to an increase in ROS damage caused by the reduced POX activity. Overexpression of DSM1 in rice increased the tolerance to dehydration stress at the seedling stage. Together, these results suggest that DSM1 might be a novel MAPKKK functioning as an early signaling component in regulating responses to drought stress by regulating scavenging of ROS in rice.

Quantitative expression analysis of drought responsive genes in clones of Hevea with varying levels of drought tolerance

“…MAPK signaling triggers expression of a cascade of genes that are involved in cellular protection, desiccation tolerance, ROS scavenging enzymes and DNA damage repair by activating corresponding transcription factors (Neill et al 2002a, b;Hung et al 2005;Desikan et al 2000). Involvement of MAPKs in abiotic stress adaptation has been widely reported in many plant species (Yu et al 2010;Ning et al 2010 The transcript abundance of Nuclear Factor Y subunit A (NFYA) was found more in RRIM 600 and RRII 105 while it was moderate in RRII 208. But it got slightly down regulated in RRII 414.…”

SALT-RESPONSIVE ERF1 Regulates Reactive Oxygen Species-Dependent Signaling during the Initial Response to Salt Stress in Rice

“…Upstream signals activate MAP3Ks, which then phosphorylate MAP2Ks. MAP2Ks in turn activate a specific MAPK (Ning et al, 2010). Moreover, MAPK cascades represent wellknown ROS-activated signaling networks involved in several abiotic stress pathways (Mittler et al, 2011).…”

“…Several members of the rice MAPK pathway are encoded by abiotic stress-responsive genes (Jung et al, 2010). In rice, the MAPK kinase kinase (MAP3K)-encoding gene DROUGHT-HYPERSENSITIVE MUTANT1 confers drought stress tolerance by regulating ROS scavenging (Ning et al, 2010). Likewise, MAPK5 confers enhanced tolerance to salt and osmotic stress when overexpressed (Xiong and Yang, 2003).…”

MAPK cascades and major abiotic stresses

“…In rice (Oryza sativa), Ning et al (2010) have identified a Raf-like MAPKKK protein, named DSM1 (drought sensitive mutant1) that functions as a potential scavenger of the reactive oxygen species (ROS), increasing plant tolerance to dehydration under water stress. Drought tolerance in rice is also enhanced by overexpression of the MAP kinase OsMAPK5, an ortholog of the Arabidopsis MPK3 (Xiong and Yang 2003).…”