Search

Pepper (Capsicum annuum L.) and tomato (Solanum lycopersicum L.), which belong to the Solanaceae family, are among the most cultivated and consumed fleshy fruits worldwide and constitute excellent sources of many essential nutrients, such as vitamins A, C, and E, calcium, and carotenoids. While fruit ripening is a highly regulated and complex process, tomato and pepper have been classified as climacteric and non-climacteric fruits, respectively. These fruits differ greatly in shape, color composition, flavor, and several other features which undergo drastic changes during the ripening process. Such ripening-related metabolic and developmental changes require extensive alterations in many cellular and biochemical processes, which ultimately leads to fully ripe fruits with nutritional and organoleptic features that are attractive to both natural dispersers and human consumers. Recent data show that reactive oxygen and nitrogen species (ROS/RNS) are involved in fruit ripening, during which molecules, such as hydrogen peroxide (HO), NADPH, nitric oxide (NO), peroxynitrite (ONOO -), and S-nitrosothiols (SNOs), interact to regulate protein functions through post-translational modifications. In light of these recent discoveries, this review provides an update on the nitro-oxidative metabolism during the ripening of two of the most economically important fruits, discusses the signaling roles played by ROS/RNS in controlling this complex physiological process, and highlights the potential biotechnological applications of these substances to promote further improvements in fruit ripening regulation and nutritional quality. In addition, we suggest that the term € nitro-oxidative eustress' with regard to fruit ripening would be more appropriate than nitro-oxidative stress, which ultimately favors the consolidation of the plant species.

Nitric oxide (NO) is an important signaling molecule occurring in virtually all organisms, whose mechanism of action relies mainly on its interaction with proteins or peptides by nitrosylation, forming compounds such as S-nitrosothiols (SNO). The Saville reaction and the ozone-based chemiluminescence method are the main techniques used for nitrosylated protein quantification. While the Saville assay is not very sensitive, the ozone-based chemiluminescence is expensive and time-consuming. Here we propose a method in which the protein-bound NO groups are exposed to UV light, cleaving the bond and allowing the quantification of the derived NO molecules by diamino-rhodamine (DAR) dyes. The DAR-based method was shown to be specific in plant tissues by pre-treatment of the samples with reducing agents and parallel EPR analysis. Spike-and-recovery assays revealed 72% recovery after a GSNO spike. Moreover, the method was significantly more sensitive than the Saville reaction, and this increase in sensitivity was crucial for detecting the reduced levels of nitrosylated proteins in plant species other than Arabidopsis. The method presented here is a suitable alternative to compare plant samples, allowing simple and fast detection of nitrosylated proteins.