Abstract
Nitric oxide (NO) is a key redox-active, small molecule involved in various aspects of plant growth and development. Here, we report the identification of an NO accumulation mutant, nitric oxide excess1 (noe1), in rice (Oryza sativa), the isolation of the corresponding gene, and the analysis of its role in NO-mediated leaf cell death. Map-based cloning revealed that NOE1 encoded a rice catalase, OsCATC. Furthermore, noe1 resulted in an increase of hydrogen peroxide (H(2)O(2)) in the leaves, which consequently promoted NO production via the activation of nitrate reductase. The removal of excess NO reduced cell death in both leaves and suspension cultures derived from noe1 plants, implicating NO as an important endogenous mediator of H(2)O(2)-induced leaf cell death. Reduction of intracellular S-nitrosothiol (SNO) levels, generated by overexpression of rice S-nitrosoglutathione reductase gene (GSNOR1), which regulates global levels of protein S-nitrosylation, alleviated leaf cell death in noe1 plants. Thus, S-nitrosylation was also involved in light-dependent leaf cell death in noe1. Utilizing the biotin-switch assay, nanoliquid chromatography, and tandem mass spectrometry, S-nitrosylated proteins were identified in both wild-type and noe1 plants. NO targets identified only in noe1 plants included glyceraldehyde 3-phosphate dehydrogenase and thioredoxin, which have been reported to be involved in S-nitrosylation-regulated cell death in animals. Collectively, our data suggest that both NO and SNOs are important mediators in the process of H(2)O(2)-induced leaf cell death in rice.
Highlights
Nitric oxide (NO) is a key redox-active, small molecule involved in various aspects of plant growth and development
No signs of damage were developed in the shaded parts of the leaves of noe1 grown in the field under natural growth conditions or under low light (400 mmol m22 s21; Supplemental Fig. S1, A and C)
When the 10-d-old low-light-grown noe1 plants were transferred to high light, the obvious leaf bleaching and cell death were developed in noe1 plants on the 2nd and 5th d, respectively (Supplemental Fig. S2A)
Summary
Nitric oxide (NO) is a key redox-active, small molecule involved in various aspects of plant growth and development. To generate insights into the potential role of S(NO) in the process of rice (Oryza sativa) leaf cell death and identify associated S-nitrosylated proteins, we conducted a forward genetic screen utilizing a large T-DNA-tagged population to identify mutants with perturbed (S)NO homeostasis. This approach uncovered the nitric oxide excess (noe1) mutant, which accumulated more (S)NO in comparison with wild-type plants. Through the biotin-switch assay and nanoliquid chromatographytandem mass spectrometry (LC-MS/MS), we identified S-nitrosylated proteins during cell death triggered by high light These results provide initial insights into the mechanisms underpinning this process in rice leaves
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