Identification of <i>Peroxiredoxin</i> (<i>PRX</i>) Genes from Pepper Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO)
Peroxiredoxins (Prxs; EC 1.11.1.15) are a group of thiol peroxidases that catalyze the detoxification of H<sub>2</sub>O<sub>2</sub> and other organic hydroperoxides. The ripening of pepper (<i>Capsicum annuum</i> L.) fruit involves significant phenotypic, physiolo...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Antioxidants |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-3921/14/7/817 |
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| Summary: | Peroxiredoxins (Prxs; EC 1.11.1.15) are a group of thiol peroxidases that catalyze the detoxification of H<sub>2</sub>O<sub>2</sub> and other organic hydroperoxides. The ripening of pepper (<i>Capsicum annuum</i> L.) fruit involves significant phenotypic, physiological, and biochemical changes. Based on the available pepper plant genome, eight <i>PRX</i> genes were identified and named <i>CaPRX1</i>, <i>CaPRX1-Cys</i>, <i>CaPRX2B</i>, <i>CaPRX2E</i>, <i>CaPRX2F</i>, <i>CaPRX2-CysBAS1</i>, <i>CaPRX2-CysBAS2</i>, and <i>CaPRX Q</i>. Among these, only CaPRX1-Cys was not detected in the transcriptome (RNA-Seq) of sweet pepper fruits reported previously. This study analyzes the modulation of these seven <i>CaPRX</i> genes during ripening and after treating fruits with nitric oxide (NO) gas. A time-course expression analysis of sweet pepper fruit during ripening revealed that two genes were upregulated (<i>CaPRX1</i> and <i>CaPRX2E</i>), two were downregulated (<i>CaPRX2B</i> and <i>PRX Q</i>), and three were unaffected (<i>CaPRX2F</i>, <i>CaPRX2-CysBAS1</i>, and <i>CaPRX2-CysBAS2</i>). Gene expression was also studied in three hot pepper varieties with varying capsaicin contents (<i>Piquillo</i> < <i>Padrón</i> < <i>Alegría riojana</i>), showing a differential expression pattern during ripening. Furthermore, NO treatment of sweet pepper fruits triggered the upregulation of <i>CaPRX2B</i> and <i>CaPRXQ</i> genes and the downregulation of <i>CaPRX1</i> and <i>CaPRX2-CysBAS1</i> genes, while the other three remained unaffected. Among the CaPrx proteins, four (<i>CaPrx2B</i>, <i>CaPrx2-CysBAS1</i>, <i>CaPrx2-CysBAS2</i>, and <i>CaPrx2E</i>) were identified as susceptible to <i>S</i>-nitrosation, as determined by immunoprecipitation assays with an antibody against <i>S</i>-nitrocysteine and further mass spectrometry analyses. These findings indicate the diversification of <i>PRX</i> genes in pepper fruits and how some of them are regulated by NO, either at the level of gene expression or through protein <i>S</i>-nitrosation, a NO-promoting post-translational modification (PTM). Given that Prxs play a crucial role in stress tolerance, these data suggest that Prxs are vital components of the antioxidant system during pepper fruit ripening, an event that is accompanied by physiological nitro-oxidative stress. |
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| ISSN: | 2076-3921 |