Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.3.1 (NADPH oxidase)
 11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

OsRac1, one of the Rac/Rop family of small GTPases, plays important roles in defense responses, including a role in the production of reactive oxygen species mediated by NADPH oxidase. We have identified an effector of OsRac1, namely rice (Oryza sativa) cinnamoyl-CoA reductase 1 (OsCCR1), an enzyme involved in lignin biosynthesis. Lignin, which is polymerized through peroxidase activity by using H(2)O(2) in the cell wall, is an important factor in plant defense responses, because it presents an undegradable mechanical barrier to most pathogens. Expression of OsCCR1 was induced by a sphingolipid elicitor, suggesting that OsCCR1 participates in defense signaling. In in vitro interaction and two-hybrid experiments, OsRac1 was shown to bind OsCCR1 in a GTP-dependent manner. Moreover, the interaction of OsCCR1 with OsRac1 led to the enzymatic activation of OsCCR1 in vitro. Transgenic cell cultures expressing the constitutively active OsRac1 accumulated lignin through enhanced CCR activity and increased reactive oxygen species production. Thus, it is likely that OsRac1 controls lignin synthesis through regulation of both NADPH oxidase and OsCCR1 activities during defense responses in rice.
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PMID:Cinnamoyl-CoA reductase, a key enzyme in lignin biosynthesis, is an effector of small GTPase Rac in defense signaling in rice. 1638 Apr 17

Development, abiotic and biotic stress each affect the physical architecture and chemical composition of the plant cell wall, making maintenance of cell-wall integrity an important component of many plant processes. Cellulose biosynthesis inhibition (CBI) was employed to impair the functional integrity of the cell wall, and the plant's response to this specific stress was characterized in an Arabidopsis seedling model system. CBI caused changes in the expression of genes involved in mechanoperception, the response to microbial challenge, and lignin and cell-wall polysaccharide biosynthesis. Following CBI, activation of a UDP-D-xylose 4-epimerase gene correlated with increases in arabinose and uronic acid content in seedling cell walls. Activation of pathogen response genes, lignin deposition and lesion formation were dependent on externally supplied sugars and were suppressed by osmotic support. Lignin deposition in the root elongation zone caused by CBI was reduced in atrbohd (NADPH oxidase) mutant seedlings but increased in jasmonic acid resistant1 (jar1-1) mutant seedlings. Phytohormone measurements showed that CBI-induced increases in jasmonic (JA) and salicylic acids were dependent on sugar availability and prevented by osmotic support. We show that CBI activates responses commonly attributed to both abiotic and microbial challenges. Glucose/sucrose and turgor pressure are critical components in maintenance of cell-wall integrity and the regulation of induced responses, including JA biosynthesis. Lignin deposition induced by CBI is regulated by JAR1-1 and NADPH oxidase-dependent signalling processes. Our results identify components of the mechanism that mediates the response to impairment of cell-wall integrity in Arabidopsis thaliana.
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PMID:Identification of cell-wall stress as a hexose-dependent and osmosensitive regulator of plant responses. 1903 34

The plant cell wall is a dynamic and complex structure whose functional integrity is constantly being monitored and maintained during development and interactions with the environment. In response to cell wall damage (CWD), putatively compensatory responses, such as lignin production, are initiated. In this context, lignin deposition could reinforce the cell wall to maintain functional integrity. Lignin is important for the plant's response to environmental stress, for reinforcement during secondary cell wall formation, and for long-distance water transport. Here, we identify two stages and several components of a genetic network that regulate CWD-induced lignin production in Arabidopsis (Arabidopsis thaliana). During the early stage, calcium and diphenyleneiodonium-sensitive reactive oxygen species (ROS) production are required to induce a secondary ROS burst and jasmonic acid (JA) accumulation. During the second stage, ROS derived from the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG D and JA-isoleucine generated by JASMONIC ACID RESISTANT1, form a negative feedback loop that can repress each other's production. This feedback loop in turn seems to influence lignin accumulation. Our results characterize a genetic network enabling plants to regulate lignin biosynthesis in response to CWD through dynamic interactions between JA and ROS.
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PMID:Cell wall damage-induced lignin biosynthesis is regulated by a reactive oxygen species- and jasmonic acid-dependent process in Arabidopsis. 2613 Jan 2

The precise localization of extracellular matrix and cell wall components is of critical importance for multicellular organisms. Lignin is a major cell wall modification that often forms intricate subcellular patterns that are central to cellular function. Yet the mechanisms of lignin polymerization and the subcellular precision of its formation remain enigmatic. Here, we show that the Casparian strip, a lignin-based, paracellular diffusion barrier in plants, forms as a precise, median ring by the concerted action of a specific, localized NADPH oxidase, brought into proximity of localized peroxidases through the action of Casparian strip domain proteins (CASPs). Our findings in Arabidopsis provide a simple mechanistic model of how plant cells regulate lignin formation with subcellular precision. We speculate that scaffolding of NADPH oxidases to the downstream targets of the reactive oxygen species (ROS) that they produce might be a widespread mechanism to ensure specificity and subcellular precision of ROS action within the extracellular matrix.
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PMID:A mechanism for localized lignin deposition in the endodermis. 2358 19