Nitric oxide (NO) has been associated with plant defense responses during microbial attack, and with induction and/or regulation of programmed cell death. Here, we addressed whether NO participates in wound responses in Arabidopsis thaliana (L.) Heynh. Real-time imaging by confocal laser-scanning microscopy in conjunction with the NO-selective fluorescence indicator 4,5-diaminofluorescein diacetate (DAF-2 DA) uncovered a strong NO burst after wounding or after treatment with JA. The NO burst was triggered within minutes, reminiscent of the oxidative burst during hypersensitive responses. Furthermore, we were able to detect NO in plants (here induced by wounding) by means of electron paramagnetic resonance measurements using diethyldithiocarbamate as a spin trap. When plants were treated with NO, Northern analyses revealed that NO strongly induces key enzymes of jasmonic acid (JA) biosynthesis such as allene oxide synthase (AOS) and lipoxygenase (LOX2). On the other hand, wound-induced AOS gene expression was independent of NO. Furthermore, JA-responsive genes such as defensin (PDF1.2) were not induced, and NO induction of JA-biosynthesis enzymes did not result in elevated levels of JA. However, treatment with NO resulted in accumulation of salicylic acid (SA). In transgenic NahG plants (impaired in SA accumulation and/or signaling), NO did induce JA production and expression of JA-responsive genes. Altogether, the presented data demonstrate that wounding in Arabidopsis induces a fast accumulation of NO, and that NO may be involved in JA-associated defense responses and adjustments.
To determine whether an unbalanced redox state might accompany the development of particular inherited mouse cataracts, the lenticular content of oxidized glutathione (GSSG) and the activity of superoxide dismutase (SOD) were chosen as markers. For wild-type lenses, an enhanced GSSG content could be observed in females as compared to males. Such a sex effect could not be detected for the SOD activity. In the mutants, GSSG content in cataractous lenses was found to be enhanced in 2 of 7 cases; the increases in other mutants were not significant. Changes of the SOD activity were even less consistent and only a random correlation of GSSG content and SOD activity with cataractogenesis could be deduced.
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