Nitric oxide-dependent posttranslational modification in plants: an update

Abstract

Nitric oxide (NO) has been demonstrated as an essential regulator of several physiological processes in plants. The understanding of the molecular mechanism underlying its critical role constitutes a major field of research. NO can exert its biological function through different ways, such as the modulation of gene expression, the mobilization of second messengers, or interplays with protein kinases. Besides this signaling events, NO can be responsible of the posttranslational modifications (PTM) of target proteins. Several modifications have been identified so far, whereas metal nitrosylation, the tyrosine nitration and the S-nitrosylation can be considered as the main ones. Recent data demonstrate that these PTM are involved in the control of a wide range of physiological processes in plants, such as the plant immune system. However, a great deal of effort is still necessary to pinpoint the role of each PTM in plant physiology. Taken together, these new advances in proteomic research provide a better comprehension of the role of NO in plant signaling.

Figure 1

Schematic illustration of NO dependent PTM in plants. To date, all the analyses of NO-modified proteins in plants followed an NO production induced by (a)biotic stress or NO donors treatment. The NO radical can react with transition metals (M) of metalloproteins. This process is called metal nitrosylation and can affect notably (non)-symbiotic hemoglobins (nsHb and sHb) and an Arabidopsis thaliana NO-dependent guanylate cyclase (AtNOGC1). The Tyr nitration depends on the formation of NO derivatives, particularly peroxynitrite formed in the presence of the superoxide anion (O2^•−). Nitration occurs on one of the two carbon equivalent (C3) of the aromatic ring of tyrosine residues to form a 3-nitrotyrosine. This reaction has been demonstrated in plants for the ferredoxin-NADP oxidoreductase (FNR), the guanylate cyclase of Medicago truncatula (MtGS1a) or the of O-acetylserine(thiol)lyase A1 (OASA1). Protein S-nitrosylation is the electrophilic attack of nitrosonium cation (NO⁺, resulting from the oxidation of NO) on a thiolate group of a cysteine residue of a target protein. Among numerous proteins, this posttranslational modification affect for example peroxyredoxin II E (PrxII E), salicylic acid binding protein 3 (SABP3), nonexpressor of pathogenesis-related gene 1 (NPR1), transcription factor TGA1, respiratory burst oxidase homologue D (RBOHD) or cell division cycle 48 (CDC48). All these modifications will participate to the change of the plant cell physiology depending on the stimulus applied.