Abstract
Main conclusionNitro/oxidative modifications of proteins and RNA nitration resulted from altered peroxynitrite generation are elements of the indirect mode of action of canavanine and meta-tyrosine in plantsEnvironmental conditions and stresses, including supplementation with toxic compounds, are known to impair reactive oxygen (ROS) and reactive nitrogen species (RNS) homeostasis, leading to modification in production of oxidized and nitrated derivatives. The role of nitrated and/or oxidized biotargets differs depending on the stress factors and developmental stage of plants. Canavanine (CAN) and meta-tyrosine (m-Tyr) are non-proteinogenic amino acids (NPAAs). CAN, the structural analog of arginine, is found mostly in seeds of Fabaceae species, as a storage form of nitrogen. In mammalian cells, CAN is used as an anticancer agent due to its inhibitory action on nitric oxide synthesis. m-Tyr is a structural analogue of phenylalanine and an allelochemical found in root exudates of fescues. In animals, m-Tyr is recognized as a marker of oxidative stress. Supplementation of plants with CAN or m-Tyr modify ROS and RNS metabolism. Over the last few years of our research, we have collected the complex data on ROS and RNS metabolism in tomato (Solanum lycopersicum L.) plants exposed to CAN or m-Tyr. In addition, we have shown the level of nitrated RNA (8-Nitro-guanine) in roots of seedlings, stressed by the tested NPAAs. In this review, we describe the model of CAN and m-Tyr mode of action in plants based on modifications of signaling pathways induced by ROS/RNS with a special focus on peroxynitrite induced RNA and protein modifications.
Highlights
CGMP Guanosine 3′,5′-cyclic monophosphate GSNO S-Nitrosoglutathione histone deacetylases (HDACs) Histone deacetylase m-Tyr meta-tyrosine nitric oxide (NO) Nitric oxide non-proteinogenic amino acids (NPAAs) Non-proteinogenic amino acid ONOO− Peroxynitrite post-translational modifications (PTMs) Posttranslational modification reactive nitrogen species (RNS) Reactive nitrogen species ROS Reactive oxygen species
Leaves and seeds of leucanea (Leucanea leucophala Lam. de Witt), a leguminosae tree, contain mimosine (Crawford et al 2015). This NPAA acts as a chelator of transition metals and its uptake by non-ruminant animals leads to alopecia (Sethi and Kulkarni 1995; Crawford et al 2015)
Plants supplementation with CAN for 24 h did not change the content of 8-NO2-G in comparison to the seedlings grown in water, while 48 h longer exposition of the seedlings to this NPAA resulted in decreased 8-NO2-G content to about 50% of the control, independently of the dose (Table 1)
Summary
Planta (2020) 252:5 non-proteinogenic amino acids (NPAAs) occur in nature; most of them are of plant or microbial origin (Bell 2003; Vranova et al 2011; Rodgers 2014). NPAAs play various roles in animals and plants: they are agents of the cellular signaling network, structural components of cell membranes and metabolic intermediates They participate in ecological interactions by acting as feeding deterrents or allelochemicals. Meta-tyrosine (m-Tyr, L-3-hydroxyphenylalanine) is a structural analogue of proteinogenic amino acid-phenylalanine (Bertin et al 2007) (Fig. 1). This NPPA is released into the environment by fine-leaf fescue grasses In animal cells m-Tyr is considered as a marker of oxidative stress and aging (Matayatsuk et al 2007) Increased level of this NPAA is typical for patients suffering from neurodegenerative diseases such as Alzheimer, a progression of which is linked to reactive oxygen species (ROS) overproduction and disturbances in reactive nitrogen species (RNS) metabolism (Hannibal 2016) 8-NO2-G in DNA may be potentially mutagenic yielding G:C to T:A transversion. 8-NO2-G in RNA is more stable than in DNA (Masuda et al 2002). 8-NO2-G incorporated into RNA may alter RNA
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